HomeMy WebLinkAboutPA2008-179_20220825_Mariners Medical Arts Conformance Review Memo
MEMORANDUM
DATE: August 25, 2022
TO: Jaime Murillo, AICP, Principal Planner
City of Newport Beach
Community Development Department
FROM: Robert Chattel, AIA, President
Alvin-Christian Nuval, Associate III
Chattel, Inc., Historic Preservation Consultants
RE: Conformance Review of Rehabilitation Plans
Mariners Medical Arts, 1901 Westcliff Drive, Newport Beach, California
Chattel, Inc (Chattel) is providing this memorandum to the City of Newport Beach (City) to describe
and assess proposed work at Mariners Medical Arts, 1901 Westcliff Drive, Newport Beach,
California (“subject property” or “complex”) to ensure conformance with the Secretary of the Interior’s
Standards for the Treatment of Historic Properties (Secretary’s Standards). The subject property
contains a 1963 medical office complex designed by master architect Richard Neutra (Neutra) and
comprised of three component buildings on a nearly square-shaped parcel. The subject property is
not listed in the National Register of Historic Places (National Register), California Register of
Historical Resources (California Register), or the local Newport Beach Register of Historical Property
(Newport Beach Register), though it was identified as the Westcliff Medical Building in a 1991
Historic Resources Inventory prepared by the City Ad Hoc Historic Preservation Advisory
Committee.
In 2008, Chattel prepared a Historic Resource Assessment (2008 HRA) for the City reviewing if the
subject property is a historical resource for the purposes of the California Environmental Quality Act
(CEQA). The 2008 HRA found that the subject property was eligible for listing in the National
Register at the statewide level of significance under Criterion C for architecture, California Register
under Criterion 3 as an exceptional work of a master architect, and Newport Beach Register as a
Class 1 – Major Historic Landmark due to its statewide significance. As such, it is a historical
resource under CEQA. Chattel subsequently prepared a Conformance Review and Cultural
Resources Impacts Analysis in 2012 for an unrealized project (2012 Report).
The subject property has since been purchased by new owners Burnham Ward Properties (BWP),
who have engaged architects ShubinDonaldson (SD) to prepare a rehabilitation drawing set for the
subject property (proposed project). Because the subject property is a historical resource under
CEQA, this memo reviews architectural and landscape plans for the subject property for
conformance with the Secretary’s Standards. The drawings prepared by SD and submitted to the
City for plan check (submittal set) are dated July 11, 2022. It should be noted that a separate
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signage program has been prepared that is not part of the submittal set. See Attachment A for
historic images, Attachment B for contemporary photos, Attachment C for original Neutra drawings,
Attachment D for Preservation Brief 1: Cleaning and Water-Repellent Treatments for Historic
Masonry Buildings, and Attachment E for Preservation Brief 6: Dangers of Abrasive Cleaning to
Historic Buildings.
Regulatory Setting
California Environmental Quality Act (CEQA)
According to CEQA,
a historical resource is a resource listed in, or determined eligible for listing in, the California
Register of Historical Resources. Historical resources included in a local register of historical
resources..., or deemed significant pursuant to criteria set forth in subdivision (g) of Section
5024.1, are presumed to be historically or culturally significant for purposes of this section,
unless the preponderance of the evidence demonstrates that the resource is not historically
or culturally significant (Public Records Code §21084.1).
If a proposed project were expected to cause substantial adverse change in an historical resource,
environmental clearance for the project would require mitigation measures to reduce impacts.
“Substantial adverse change in the significance of an historical resource means the physical
demolition, destruction, relocation, or alteration of the resource or its immediate surroundings such
that the significance of an historical resource would be materially impaired.”1 California Code of
Regulations, Title 14, Chapter 3 §15064.5 (b)(2) describes material impairment taking place when a
project:
A) demolishes or materially alters in an adverse manner those physical characteristics
of an historical resource that convey its historical significance and that justify its
inclusion in, or eligibility for, inclusion in the California Register… or
B) demolishes or materially alters in an adverse manner those physical; characteristics
that account for its inclusion in a local register... or its identification in an historical
resources survey... unless the public agency reviewing the effects of the project
establishes by a preponderance of evidence that the resource is not historically or
culturally significant; or
C) demolishes or materially alters those physical characteristics of an historical resource
that convey its historical significance and that justify its inclusion in, or eligibility for,
inclusion in the California Register... as determined by a lead agency for the
purposes of CEQA.
California Historical Building Code (CHBC)
The purpose of the CHBC is to provide regulations for preservation, restoration, rehabilitation,
relocation, or reconstruction of buildings or properties designated as qualified historical buildings or
properties. A qualified historical building or property, as defined by CHBC and Health and Safety
Code Section 18955, is:
Any building, site, object, place, location, district or collection of structures, and their
associated sites, deemed of importance to the history, architecture or culture of an area by
an appropriate local, state, or federal government jurisdiction. This shall include historical
buildings or properties on, or determined eligible for, national, state or local historical
1 CEQA Guidelines §15064.5 (b)(1))
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registers or inventories, such as the National Register of Historic Places, California Register
of Historical Resources, State Historical Landmarks, State Points of Historical Interest, and
city or county registers, inventories or surveys of historical or architecturally significant sites,
places or landmarks.
Secretary of the Interior’s Standards for the Treatment of Historic Properties
The Secretary’s Standards are not intended to be prescriptive and are intended to be flexible and
adaptable to specific project conditions to balance continuity and change while retaining historic
building fabric to the maximum extent feasible. Their interpretation requires exercise of professional
judgment and balance of the various opportunities and constraints of any given project based on
use, materials retention and treatment, and compatibility of new construction. Not every standard
necessarily applies to every aspect of a project, nor is it necessary to comply with every standard to
achieve conformance. The Secretary’s Standards encompass four approaches to treatments for
historic properties: preservation, rehabilitation, restoration, and reconstruction. The appropriate
treatment for the proposed project is rehabilitation, defined as the Secretary of the Interior’s
Standards for Rehabilitation (Rehabilitation Standards).
The Rehabilitation Standards are as follows:
1. A property will be used as it was historically or be given a new use that requires minimal
change to its distinctive materials, features, spaces, and spatial relationships.
2. The historic character of a property will be retained and preserved. The removal of distinctive
materials or alteration of features, spaces, and spatial relationships that characterize a
property will be avoided.
3. Each property will be recognized as a physical record of its time, place, and use. Changes
that create a false sense of historical development, such as adding conjectural features or
elements from other historic properties, will not be undertaken.
4. Changes to a property that have acquired historic significance in their own right will be
retained and preserved.
5. Distinctive materials, features, finishes, and construction techniques or examples of
craftsmanship that characterize a property will be preserved.
6. Deteriorated historic features will be repaired rather than replaced. Where the severity of
deterioration requires replacement of a distinctive feature, the new feature will match the old
in design, color, texture, and, where possible, materials. Replacement of missing features
will be substantiated by documentary and physical evidence.
7. Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means
possible. Treatments that cause damage to historic materials will not be used.
8. Archeological resources will be protected and preserved in place. If such resources must be
disturbed, mitigation measures will be undertaken.
9. New additions, exterior alterations, or related new construction will not destroy historic
materials, features, and spatial relationships that characterize the property. The new work
will be differentiated from the old and will be compatible with the historic materials, features,
size, scale and proportion, and massing to protect the integrity of the property and its
environment.
10. New additions and adjacent or related new construction will be undertaken in such a manner
that, if removed in the future, the essential form and integrity of the historic property and its
environment would be unimpaired.
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General Existing Conditions
Mariners Medical Arts at 1901 Westcliff Drive is located at the center of a rectangular block bounded
by Westcliff Drive (Westcliff) to the north, Irvine Avenue to the west, Dover Drive to the east, and
Sherington Place (Sherington) to the south. The immediate setting is primarily commercial, though
adjacent blocks also have single-family and multi-family residences. The primary façade of the
subject property faces Westcliff and the buildings are set back from the street by a drive aisle
separating two rows of perpendicular parking along the north at Buildings A and B. Along Sherington
there is additional rear parking with a drive aisle and a single row of perpendicular parking along the
south at Building C. Commercial property is located to the east and west.
The subject property includes three buildings organized by outdoor walkways covered by a main
north-south canopy and a secondary east-west canopy (circulation canopies). Together, the
buildings form an L-shaped plan, with Buildings A and B at the north and Buildings B and C at the
east. There are ten total existing suites, with four in one-story Building A (2, 3A, 7, 7A), two in one-
story Building B (1, 4), and four in two-story Building C (6, 9, 5, 10). Building A is the largest of the
three buildings at 9,000 square feet, followed by Building C at 6,150 square feet, and Building B at
2,350 square feet. The circulation canopies delineate the primary path of travel at the subject
property. The main circulation canopy, considered the central spine, runs north-south between
Buildings A and B, from the entrance at the north elevation to Building C. The circulation canopies
are generally freestanding; the underside of the north-south canopy is plaster and the underside of
the east-west canopy is corrugated metal. Building A has a full width carport located on the west
elevation. It should be noted that the carport is screened from both Westcliff and Sherington.
The buildings are primarily clad in stucco and ashlar masonry walls, but glass, metal, and wood are
also used throughout. Fenestration is typically arranged in groups and read as long, linear strips,
emphasizing the horizontal massing of the buildings. Vertical elements such as metal louvers and
wood screen walls are also reflected throughout. The roofs are generally flat with either a short
parapets or extended eaves. Added rooftop mechanical equipment is visible on one-story Buildings
A and B, and less so on two-story Building C.
Hardscape generally consists of simple gray concrete paving with regular control joints. There are
several locations where there has been differential settlement of concrete paving causing trip
hazards. A ramp from the rear parking is particularly steep. Parking areas are covered in asphalt
paving.
Landscaping generally occurs adjacent to exterior walls of the buildings and at planters within or
adjacent to the parking and along the central spine. There is a wide variety of planting including a
lawn, olive, pine and eucalyptus trees, and palms. On May 26, 2022, Arborgate Consulting, Inc.
(Arborgate) prepared an arboricultural evaluation (Arborgate evaluation) of 30 trees at the subject
property. The evaluation found several deficiencies including lack of proper professional pruning that
has been harmful to the health, structure, and beauty of the trees. Olive trees were found to have
minor to severe Xylella infections that cannot be cured. Arborgate described the following in their
analysis:
The buildings themselves may have historical interest or connection to a notable architect,
but the landscape and the trees are now common. The spaces that contain the various trees
are inadequate to provide for many more years of life. The pruning and other care of the
trees will not help these trees have long lives. Truly historic trees are planted in places where
they can live long lives. Those conditions do not exist here.
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Hardscape elements include a circular concrete bench with flagpole at center, three historic
rectangular water features below the north-south canopy that are not in operation, and a concrete
bicycle parking pad at the north elevation of Building B.
The 2012 Report describes character-defining features of the subject property as follows:
• Horizontality of overall design with a low-flung nature
• Interplay of vertical and horizontal planes achieving balance through composition of
asymmetrical parts
• Configuration of buildings as a complex, and a strong relationship of buildings to each other
and the site
• Flat roofs with wide overhanging eaves and cantilevered canopies, some with skylights or
oculus opening to the sky
• Relationship between exterior and interior spaces
• Configuration of contained interior and public exterior courtyards
• Exterior circulation pattern, including patio-lobby
• Landscape features, particularly olive and eucalyptus trees
• Low concrete planters, some originally served as reflecting pools
• Exterior staircases, second floor decks, and walled patios
• Simple, geometric forms
• Expressed post-and-beam construction
• Steel, round- and square-shaped canopy supports
• Ribbon and clerestory windows, with fixed and louvered panes
• Exterior stone cladding and wood screen walls
• Unadorned wall surfaces; little decorative detailing throughout
• Palette of materials in a variety of shades and textures; including stone exterior cladding,
painted plaster walls, steel, and glass
• Linear fluorescent lighting fixtures located at the building exterior, under roof eaves
Alterations
As described in the 2008 HRA:
Alterations to Mariners’ Medical Arts building are relatively insignificant as demonstrated both
through photographic evidence and in the record of changes to the building fabric
established by the permits over the years. Most of the permits noted relate to minor tenant
improvements on the interiors of units, such as the addition of sinks, light fixtures, or
electrical receptacles. Interiors of most units have had minor tenant alterations over the
years, such as the replacement of original cabinetry. However, the Mariners’ Medical Arts
building is a highly intact example of Neutra’s work, as major structural elements and
architectural features are relatively untouched. The building currently suffers from lack of
adequate maintenance, but this, too, in no way diminishes the building’s significance.
Additional alterations described in the 2008 HRA include loss of metal louvers at Suite 6, which were
illegally removed and reported stolen in November 2008, and changes to the central landscaped
area along the north-south canopy. Historic water features were emptied and infilled with earth
topped with a gravel or stone surface. A cast-concrete wayfinding element shaped like a podium or
table near the northernmost water feature was also removed at an unknown date.
Since preparation of the 2008 HRA, additional alterations, some unpermitted, have occurred at the
subject property, as described in the 2012 Report. The most significant change has been removal of
the stairs at the southeast corner of Building C. The stairs are still not extant, though there is a
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visible scar from where the stairs were removed. The second-floor units at Building C are currently
vacant and only accessible by the stairs at the west elevation. Additional alterations include
installation of added recessed circular can light fixtures under the eave at the façade of Building A
and along the north-south canopy, and removal of exterior stone cladding for gas line installation at
Building B. The 2012 Report concluded that even with the unpermitted work, the subject property still
retains integrity. Minimal alterations appear to have occurred since, though several character-
defining eucalyptus trees have been removed, including at the courtyard of Building A and rear
parking to the west of Building C.
Proposed Project Description
The project description contained in the submittal set states:
Exterior rehabilitation of an existing historical medical facility and non-medical offices,
including in-kind replacement of exterior materials where possible. Scope to include
architectural, structural, mechanical, plumbing, electrical, civil, and landscape. Interior
additions of 356 SF at Level 2 (E) exterior decks. All work shall be completed in conformance
with the Secretary of the Interior’s Standards for the Treatment of Historic Properties (36
CFR 38).
The three buildings at the subject property are generally undergoing similar treatments, described in
the sections below.
Exterior Walls
Existing and refinished exterior plaster surfaces would generally be painted white with an eggshell
finish. Where indicated, some walls would instead be painted in an accent chestnut color, a dark red,
matching the original Zolatone finish based on historic documentation. The existing stone walls at
the north elevation of Building A and the west elevation of Building C would be cleaned with a
muriatic acid wash. No work is proposed at the other existing stone walls at the subject property. At
the west elevation of Building C, vertical wood fins at the west of the stairs leading to the second
floor would be stripped of paint and sanded on all sides. A semi-transparent oil-based Olympic stain
would be applied and steel brackets would be restored and painted with epoxy paint. A similar
treatment would occur to the vertical wood members at the east bay south elevation of Building B.
At the north elevation of Building B, the existing wall panel between the windows and the stone wall
would be replaced with a new white composite panel. An existing panel at the west bay of the south
elevation of Building B would be treated similarly. Existing wall panels at the south elevation of
Building C would be disassembled and replaced with new gray composite panels. Some walls
directly adjacent to suite doors would have a wood composite panel in a French walnut finish.
The demolished stairs at the southeast corner of Building C, with entrance at the south elevation,
would be reconstructed based on historic documentation. A new steel handrail would be installed
along the new east pony wall and terminate at the bottom of the stairs. A new recessed LED light
would also be installed near the raked base of the new east pony wall, approximately 6 inches above
the stair tread. The partial height deck wall on the second floor at suite 10 along the west side of the
reconstructed stair is proposed to be raised to meet the roof extension and clad in stucco.
The existing address sign at the north elevation wall of Building A and south elevation of Building C
would be protected-in-place and cleaned. Added tenant signs below the address sign at Building A
would be removed, with holes patched to match existing plaster.
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Doors and Windows
All existing suite entry doors would be replaced with new solid core wood doors with French walnut
finish. Architect has instructed the general contractor to verify if existing frames for doors at specified
suites are aluminum storefront or wood. Suite doors vary between flush single with wood frame,
flush single with no frame at existing storefront, and flush single with wood frame and wood transom
panel. Existing original suite numbers would be salvaged for re-installation on new doors. All original
mail slot next to the existing suite entry doors would be restored where existing. Utility doors would
generally be replaced with vertical cedar slat doors painted either chestnut to match original
Zolatone color or white with eggshell finish to match painted plaster walls. The existing four-panel
sliding glass door assembly at the second-floor east wall of Building C would be removed and
prepped for a new fixed glazing assembly.
All existing windows and frames would be cleaned to remove corrosion using the gentlest means
possible, with clear film applied to original glazing from the interior. New storefronts at the second
floor of Building C would have glass with clear anodized aluminum frames.
Vertical aluminum louvers at the subject property would generally be refinished, with special
cleaning and protection of glazing behind the louvers. New cranks would be installed where missing
to make louvers functional based on historic documentation. Missing louvers would be replaced in-
kind with matching profile and brackets. At the vertical aluminum louvers on the east and west
elevations of Building C, shoring would take place for bracket replacement, with existing wall
brackets removed and replaced with new support.
Circulation Canopies
Proposed alterations to the existing circulation canopies are largely concentrated at the central spine
running north-south between Buildings A and B and extending west along the north and south
elevations of Building A. The existing plaster ceiling and light fixtures would generally be removed,
though the four existing recessed can light fixtures with eyeball trims at the primary façade of
Building A would be protected-in-place and restored. New plaster with light sand finish would be
installed and painted white with eggshell finish. A new recessed LED linear light fixture would be
installed at the east edge of the central spine, terminating at Building C.
At the metal canopy running east-west between Buildings B and C, all corrosion at the underside
would be removed with rust remover. If the rust remover is insufficient, abrasive-blasting in a range
of No. 10 to No. 45 screen sizes and dry compressed air at 80 pounds per square inch is proposed.
All exposed structural steel at the underside of the canopy and at cylindrical pipes or columns would
be painted a red iron oxide color.
Roof
All roofs would have a new PVC single-ply roofing membrane with new aggregate or ballast
distributed evenly. A portion of existing mechanical equipment on the roof of Building A would be
demolished, along with a roof screen near the south elevation. All other existing rooftop mechanical
equipment would remain. New aluminum roof screens would be installed set back further from the
roof edge of Building A to block remaining mechanical, though a portion of existing mechanical
equipment that is substantially set back from the north elevation would not be screened. No
screening is proposed for the existing mechanical equipment at the roof above the second floor of
Building C. All existing exterior roof gutters and downspouts and all temporary, makeshift stormwater
plumbing lines would be removed. Various new galvalume sheet metal downspouts and gutters
would be installed. All existing roof edge flashing would be replaced with new galvalume flashing.
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An existing skylight in Building A would be removed and replaced in-kind, with all other existing
skylights to remain. Existing wood trellis structures at Buildings A and B would be removed and
replaced with new clear cedar beams to match existing. At Building C, a portion of the roof structure
at the southeast corner of the second floor would be removed to accommodate new roof framing and
cladding.
Interiors
No interior work is proposed except at the vacant second-floor suites (5 and 10) at Building C. All
non-load-bearing interior framing would be removed, and all existing plumbing and mechanical
fixtures would be removed and capped. The existing sliding doors at the east wall of suite 10 would
be removed. Where portion of the exterior wall at the east exterior decks would be converted to an
interior wall, plaster cladding would be removed.
The east entrance to suite 10 would be moved further east, with a new clear anodized aluminum
storefront on curb added. At the south wall where a portion of the exterior deck would be enclosed, a
new clear anodized aluminum storefront would also be added, with sliding doors allowing access to
a smaller exterior deck.
Hardscape and Landscape
Existing concrete hardscape throughout the subject property would be removed for installation of
new hardscape. Natural gray concrete would be the primary material, used for exterior circulation
throughout the subject property. Tinted concrete in a palomino color would also be used at suite
entry door locations only.
A new monument sign is proposed perpendicular to the sidewalk along Westcliff and shown for
reference in the submittal set. The existing flagpole with circular bench seating and existing bicycle
parking pad at the primary north façade would be retained, with new wood slats proposed to
encompass the top surface of the circular bench and new bollards proposed at the bicycle parking
pad. Four new vehicular bollards are proposed at the main entryway at the primary façade, as well
as truncated dome pavers in a gray charcoal color. All three existing water features would be
demolished and replaced with new water features in the same general locations. New rectangular
water features would be functional and have a concrete basin, with waterproofing and decorative
rock mulch. The water features would also be bordered by ¼-inch thick Corten steel with a 4-inch
welded dowel, embedded in the concrete pour. A layer of basalt chip rock mulch would line the
exterior perimeter of the water features. New planter pots would be added in the two southernmost
water features to match existing. At the southwest corner of the rear parking, a new trash enclosure
is proposed with access from Sherington. The trash enclosure would have cedar vertical wood slat
doors and walls, similar to the utility doors at the complex, mounted to a 2x2 angle and structural
metal beams with a web at the corners. The trash enclosure would also have a DensDeck clad shed
roof with liquid-applied waterproofing topped with gravel that extends slightly above the wood
enclosure below.
The existing wood screen to the east of Building A would be removed and replaced with a new wood
screen composed of hollow structural sections (HSS) steel posts and cedar wood planks arranged
vertically. A new concrete ramp with low wall would be installed south of Building A and west of
Building C, providing accessibility to and from the rear parking. A stainless steel handrail on posts
would border both sides of the ramp. The existing steps down from the rear parking to Building C
would be replaced with new cast-in-place concrete stairs with a steel railing.
Most existing trees and palms at the subject property are proposed to be removed, though three
Canary Island pines (pinus canariensis), one Japanese black pine (pinus thunbergiana), and two
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olive trees (olea europaea) would remain. Fifteen new olive trees would be planted throughout the
subject property, some where existing trees were removed and some in new locations at the rear
parking at the south. At the sidewalks to the north and south of the subject property, existing Port
Jackson fig trees (ficus rubiginosa) would remain. Additional new planting includes a variety of low
shrubs and grasses in bark and rock mulch alongside the covered canopies, at perimeter of the
buildings, and at both the north and south sidewalks.
Conformance with the Secretary’s Standards
Within the Secretary’s Standards, the appropriate treatment for the project is rehabilitation, defined
as the Secretary of the Interior’s Standards for Rehabilitation (Rehabilitation Standards). As is further
explained below, the project is found to conform with the Rehabilitation Standards:
• The subject property will continue to retain its historic use as a medical office complex, with
little change to its distinctive materials, features, spaces, and spatial relationships. Therefore,
the proposed project is in conformance with Standard 1.
• The project would retain and preserve the historic character of the subject property.
Features, spaces, and spatial relationships that characterize the subject property would still
be intact and interpreted appropriately. There is a concern about the proposed removal of
existing lemon gum eucalyptus trees at the subject property which have previously been
identified as a character-defining feature. The proposed project is in conformance with
Standard 2.
• The project would not create a false sense of historical development and does not include
construction of conjectural features which were never constructed. The functional water
features would be added along the central spine in a contemporary manner. There is some
concern about the proposed addition of a wood slat surface on the existing circular bench
seating at the flagpole. The circular bench historically had a concrete surface, so addition of
wood slat surface is not recommended. The applicant has since stated that they will revise
plans to remove the wood slat surface. The proposed project is in conformance with
Standard 3.
• The project does not appear to have alterations that have taken historic significance over
time. Therefore, the proposed project is in conformance with Standard 4.
• The project would preserve distinctive features, finishes, and construction techniques of the
subject property. Historic materials would be retained to the greatest extent feasible.
Character-defining features that demonstrate workmanship, such as the use of louvers
throughout the complex, would be retained and repaired as necessary. Concrete paving
would be replaced with similar material, texture, and finish with emphasis at suite doors. The
project would also return features that had been altered or removed such as the removed
stairs at the southeast corner of Building C. Therefore, the proposed project is in
conformance with Standard 5.
• Deteriorated historic features, such as damaged or missing louvers, would be repaired rather
than replaced, or if not possible, replaced in-kind. Some features that had previously been
removed, such as exterior stairs at the southeast corner of Building C, would be
reconstructed based on historic documentation. Therefore, the proposed project is in
conformance with Standard 6.
• Rust removal at the metal canopy and muriatic acid wash at stone walls are proposed. It is
currently unclear how these chemical and physical treatments will be undertaken to not
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impair historic materials. While some methods are acceptable (see Attachment D for
reservation Brief 1: Cleaning and Water-Repellent Treatments for Historic Masonry Buildings
and Attachment E for Preservation Brief 6: Dangers of Abrasive Cleaning to Historic
Buildings), mock-ups should be completed prior to the full work. The proposed project is in
conformance with Standard 7.
• There is no reason to believe that archaeological resources would be affected by the project
as the subject property had already previously been developed to build the complex.
Therefore, the proposed project is in conformance with Standard 8.
• The project would not substantially destroy historic materials that characterize the subject
property. Historic materials that are damaged would be repaired or replaced in-kind. Missing
louvers and cranks would be replaced in-kind to return functionality. Demolition of exterior
walls would be limited to a small portion of the second floor of Building C that is not highly
visible and at the rear elevation. Therefore, the proposed project is in conformance with
Standard 9.
• The project would not have any new additions or adjacent new construction which would
impair the essential form and integrity of the subject property. The size, scale, proportion,
and massing of the property would remain relatively the same. The new infill construction at
the second floor of Building C will be appropriately subordinate and follow established
fenestration patterns and use of materials. Retention of a smaller deck at the south elevation
and setting back the new glazing would maintain the existing character of the south
elevation. Therefore, the proposed project is in conformance with Standard 10.
Outstanding Recommendations and Resolution
• Lemon gum eucalyptus trees were previously identified as character-defining features in the
2012 Report. Since preparation of the 2012 Report, several eucalyptus trees have been
removed from the subject property and only five remain at the rear parking. These five
eucalyptus trees are proposed to be removed with no replacement of new eucalyptus trees,
resulting in complete loss of this character-defining feature. Chattel encourages replanting
some eucalyptus trees at the subject property in locations based on historic photographs to
reduce the overabundance of proposed replacement and added olive trees. It is unfortunate
that with implementation of the project as proposed, all remaining eucalyptus trees would be
removed from the subject property and not replaced in like kind. Justification for removal was
provided included inherent risk in replanting the same character-defining species. Thus, on
balance, the proposed project is in conformance with Standard 2.
• Do not add wood slat surface to the existing circular bench seating at flagpole. Based on
historic photographs, the seating appears to always have had a concrete surface. Addition of
wood slats adds to a false sense of history, inconsistent with the Secretary’s Standards, and
should be avoided. The applicant has since stated that they will revise plans to remove the
wood slat surface.
• Where infill is proposed at the existing partial height east wall of second-floor suite 10 at
Building C clerestory windows are recommended to interpret previous view of glass
storefront facing the exterior deck. The clerestory window detail should be similar to
clerestory windows on the north elevation at suite 2 in Building A.
• Prior to undertaking full rust removal or abrasive blasting at metal canopy and muriatic acid
wash at stone wall, prepare a small-scale mock-up to test if historic materials may be
damaged. For metalwork, abrasive blasting with fractured or round glass may be appropriate
for use under controlled conditions. For stone walls, a Prosoco product may be appropriate
for use and is recommended. Refer to Preservation Brief 1: Cleaning and Water-Repellent
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Treatments for Historic Masonry Buildings and Preservation Brief 6: Dangers of Abrasive
Cleaning to Historic Buildings for additional recommendations and treatments.
• Detailing of the galvalume and other sheet metal work at the coping of the reconstructed stair
at the southeast corner of Building C and at the gravel stop/fascia trim at the roofs should
exactly match historic documentation. Based on physical evidence, the sheet metal details
included a straited or grooved surface texture that should be the building standard for repair
and replacement, as necessary. In particular, the reconstructed pony wall should have a
grooved sheet metal cap that extends slightly to each side of the stucco wall.
• Any new mechanical equipment added to the roof of Building C or elsewhere at Buildings A
and B by future tenants should be located as close to the center of the roof as possible to be
minimally visible from the street, with screening to match proposed screening materials and
design at Building A.
Conclusion
Based on the findings of this memo, the proposed work described in the rehabilitation plans are in
conformance with the Secretary’s Standards. To supplement conformance of the proposed project,
Chattel outlined a series of recommendations in the bullets above. The City should continue to
follow-up on the recommendations with the applicant team at its discretion. The overall project
maintains the integrity and character of the subject property and proposed alterations reviewed are
compatible in design.
Attachments
Attachment A: Historic Images
Attachment B: Contemporary Photos
Attachment C: Original Neutra Drawings
Attachment D: Preservation Brief 1: Cleaning and Water-Repellent Treatments for Historic Masonry
Buildings
Attachment E: Preservation Brief 6: Dangers of Abrasive Cleaning to Historic Buildings
this pAge intentionAlly left blAnk
AttAchment A:
historic imAges
Mariners Medical arts
1901 Westcliff drive
neWport Beach, california
this pAge intentionAlly left blAnk
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 1: Subject property, Building B (left) and Building A (right), north elevation,
view south (Julius Shulman Photography Archive, Getty Research Library, 1964)
Image 2: Subject property, Building B, east (left) and north (right) elevations, view
west (Julius Shulman Photography Archive, Getty Research Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 3: Subject property, Building B, east elevation, view west (Julius Shulman
Photography Archive, Getty Research Library, 1964)
Image 4: Subject property, Building C, east elevation, view west (Julius Shulman
Photography Archive, Getty Research Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 5: Subject property, Building C, east elevation, view northeast (Yukio
Fukagawa, Richard and Dion Neutra Papers 1925-1970, UCLA Special
Collections, 1969)
this spAce intentionAlly left blAnk
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 6: Subject property, Building C, south (left) and east (right) elevations, view
north (Julius Shulman Photography Archive, Getty Research Library, 1964)
Image 7: Subject property, Building C, south elevation, view northeast (Julius
Shulman Photography Archive, Getty Research Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 8: Subject property, Building C, west elevation, view east (Julius Shulman
Photography Archive, Getty Research Library, 1964)
Image 9: Subject property, Building C, west elevation, view southeast (Julius
Shulman Photography Archive, Getty Research Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 10: Subject property, Building B (left) and Building A (right), west elevation,
view southwest (Julius Shulman in Thomas S. Hines’ Richard Neutra and the
Search for Modern Architecture, 1964)
Image 11: Subject property, Building B (left) and Building A (right), underneath
canopy at central spine, view southwest (Yukio Fukagawa, Richard and Dion
Neutra Papers 1925-1970, UCLA Special Collections, 1969)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 12: Subject property, Building B (left) and Building A (right), water fixture
and central spine visible, view west (Julius Shulman Photography Archive, Getty
Research Library, 1964)
Image 13: Subject property, Building B, west elevation, water fixture, view
southeast (Julius Shulman Photography Archive, Getty Research Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 14: Subject property, Building C, north elevation, water fixture and canopy
visible, view southwest (Julius Shulman Photography Archive, Getty Research
Library, 1964)
Image 15: Subject property, Building C, west elevation, water fixture and canopy
visible, view northeast (Julius Shulman Photography Archive, Getty Research
Library, 1964)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 16: Subject property, Building A, south (left) and east (right) elevations,
view northwest (Julius Shulman Photography Archive, Getty Research Library,
1964)
this spAce intentionAlly left blAnk
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment A: historic imAges
chAttel, inc. | historic PreservAtion consultAnts
Image 17: Subject property, north elevation, view south, note eucalyptus trees
that have been removed identified with red arrows (Google Maps, 2011)
Image 18: Subject property, south elevation, view north, note eucalyptus trees
that have been removed identified with red arrows (Google Maps, 2011)
AttAchment B:
contemporAry photogrAphs
Mariners Medical arts
1901 Westcliff drive
neWport Beach, california
this pAge intentionAlly left BlAnk
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 1: Subject property, Building A, north elevation, view northwest (Chattel,
2022)
Image 2: Subject property, Building B, north elevation, view southeast (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 3: Subject property, Building A, north elevation, view west (Chattel, 2022)
Image 4: Subject property, Building A, east elevation, view northwest (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 5: Subject property, Building B (left) and Building A (right), main entrance
with flagpole and central spine visible, view southwest (Chattel, 2022)
Image 6: Subject property, detail of circular bench at flagpole (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 7: Subject property, Building B (left) and Building A (right), detail of non-
functioning water feature and central spine (Chattel, 2022)
Image 8: Subject property, Building A (left) and Building B (right), view down
central spine towards main entrance, view northeast (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 9: Subject property, Building A, east elevation under central spine, view
north (Chattel, 2022)
Image 10: Subject property, Building A, east elevation, view northwest (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 11: Subject property, Building A, south elevation, view northwest (Chattel,
2022)
Image 12: Subject property, Building A, south elevation, view northeast (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 13: Subject property, Building A, south elevation, view east (Chattel, 2022)
Image 14: Subject property, Building A, west (left) and south (right) elevations,
view east (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 15: Subject property, Building B, north elevation, view south (Chattel, 2022)
Image 16: Subject property, Building B, north elevation, detail of bicycle parking
pad, view southwest (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 17: Subject property, Building B, east elevation, stone wall, view northwest
(Chattel, 2022)
Image 18: Subject property, Building B, south (left) and east (right) elevations,
view north (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 19: Subject property, Building B, east elevation, view northwest (Chattel,
2022)
Image 20: Subject property, Building C (left) and Building B (right), metal canopy,
view northwest (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 21: Subject property, metal canopy at east elevation, view northeast
(Chattel, 2022)
Image 22: Subject property, metal canopy at east elevation, view west (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 23: Subject property, Building C, east elevation, vertical metal louvers, view
northwest (Chattel, 2022)
Image 24: Subject property, Building C, east elevation, detail of vertical metal
louvers, view west (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 25: Subject property, Building C, east elevation, wall where stairs to
second floor was removed, scar visible, view northwest (Chattel, 2022)
Image 26: Subject property, Building C, east elevation, detail of scarring at wall
where stairs to second floor was removed, view northwest (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 27: Subject property, Building C, south elevation, view north (Chattel,
2022)
Image 28: Subject property, Building C, south elevation, view east (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 29: Subject property, Building C, north (left) and west (right) elevations,
view south (Chattel, 2022)
Image 30: Subject property, Building C, west elevation, view southeast (Chattel,
2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 31: Subject property, Building C, west elevation, vertical wood fins at stairs,
view east (Chattel, 2022)
this spAce intentionAlly left BlAnk
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 32: Subject property, Building C, west (left) and north (right) elevations,
view southwest (Chattel, 2022)
Image 33: Subject property, Building C, west elevation, view east (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 34: Subject property, Building C, detail of deterioration at canopy metal
columns (Chattel, 2022)
Image 35: Subject property, Building C, detail of original suite number at door
(Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 36: Subject property, Building C, west elevation, olive tree in landscape,
view southeast (Chattel, 2022)
Image 37: Subject property, Building C, west stairs to second floor, view
southwest (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 38: Subject property, Building C, second floor landing at west elevation,
view southwest (Chattel, 2022)
Image 39: Subject property, Building C, second floor, detail of vertical metal
louvers, note one louver missing, view southwest (Chattel, 2022)
Mariners Medical arts, 1901 Westcliff drive, neWport Beach, california
AttAchment B: contemporAry photogrAphs
chAttel, Inc. | hIstorIc preservAtIon consultAnts
Image 40: Subject property, hardscape, detail of steps and handrail from Building
C to rear parking, view northwest (Chattel, 2022)
Image 41: Subject property, hardscape, detail of ramp from Building A to rear
parking, view southwest (Chattel, 2022)
this pAge intentionAlly left BlAnk
AttAchment c:
OriginAl neutrA DrAwings
Mariners Medical arts
1901 Westcliff drive
neWport Beach, california
this pAge intentiOnAlly left blAnk
AttAchment D:
PreservAtion Brief 1 -
cleAning AnD WAter-rePellAnt treAtments
for historic mAsonry BuilDings
Mariners Medical arts
1901 Westcliff drive
neWport Beach, california
this PAge intentionAlly left BlAnk
16
Summary
A well-planned cleaning project is an essential step in
preserving, rehabilitating or restoring a historic masonry
building. Proper cleaning methods and coating treatments,
when determined necessary for the preservation of the
masonry, can enhance the aesthetic character as well as the
structural stability of a historic building. Removing years
of accumulated dirt, pollutant crusts, stains, graffiti or
paint, if done with appropriate caution, can extend the life
and longevity of the historic resource. Cleaning that is
carelessly or insensitively prescribed or carried out by
inexperienced workers can have the opposite of the intended
effect. It may scar the masonry permanently, and may
actually result in hastening deterioration by introducing
harmful residual chemicals and salts into the masonry or
causing surface loss. Using the wrong cleaning method or
using the right method incorrectly, applying the wrong
kind of coating or applying a coating that is not needed
can result in serious damage, both physically and
aesthetically, to a historic masonry building. Cleaning a
historic masonry building should always be done using
the gentlest means possible that will clean, but not damage
the building. It should always be taken into consideration
before applying a water-repellent coating or a waterproof
coating to a historic masonry building whether it is really
necessary and whether it is in the best interest of preserving
the building.
Selected Reading
Architectural Ceramics: Their History, Manufacture and
Conservation. A Joint Symposium of English Heritage and the
United Kingdom Institute for Conservation, September 22-25,
1994. London: English Heritage, 1996.
Ashurst, Nicola. Cleaning Historic Buildings. Volume One:
Substrates, Soiling & Investigation. Volume Two: Cleaning
Materials & Processes. London: Donhead Publishing Ltd., 1994.
Association for Preservation Technology. Special Issue:
Preservation of Historic Masonry. Papers from the Symposium
on Preservation Treatments for Historic Masonry: Consolidants,
Coatings, and Water Repellents, New York, New York, November
11-12,1994. APT Bulletin. Vol. XXVI, No.4 (1995).
Grimmer, Anne E. Preservation Brief 6: Dangers of Abrasive
Cleaning to Historic Buildings. Washington, D.C: Preservation
Assistance Division, National Park Service, U.s. Department
of the Interior, 1979.
Grimmer, Anne E. Ke~ping it Clean: Removing Exterior Dirt,
Paint, Stains and Graffiti ]rom Historic Masonry Buildings.
Washington, D.C.: Preservation Assistance Division, National
Park Service, U.S. Department of the Interior, 1988.
Park, Sharon c., AlA. Preservation Brief39: Holding the Line:
Controlling Unwanted Moisture in Historic Buildings.
Washington, D.C: Heritage Preservation Services, National Park
Service, U.s. Department of the Interior, 1996.
Powers, Robert M. Preservation Tech Note, Masonry No.3,
"Water Soak Cleaning of Limestone". Washington, D.C:
Preservation Assistance Division, National Park Service, U.s.
Department of the Interior, 1992.
Sinvinski, Valerie. "Gentle Blasting." Old-House Journal. Vol.
XXIV, No.4 Ouly-August 1996), pp. 46-49.
Weaver, Martin E. Conserving Buildings: A Guide to
Techniques and Materials . New York: John Wiley & Sons, Inc.,
1993.
Weaver, Martin E. Preservation Brief 38: Removing Graffiti from
Historic Masonry. Washington, D.C: Preservation Assistance
Division, National Park Service, U.S. Department of the Interior,
1995.
Winkler, E.M. Stone in Architecture: Properties, Durability.
Third, completely revised and extended edition. Berlin,
Germany: Springer-Verlag, 1997.
Acknowledgments
Robert C. Mack, FAIA, is a principal in the firm of MacDonald
& Mack Architects, Ltd., an architectural firm that specializes in
historic buildings in Minneapolis, Minnesota.
Anne Grimmer is a Senior Architectural Historian in the Technical
Preservation Services Branch, Heritage Preservation Services
Program, National Park Service, Washington, D.C
The original version of Preservation Brief 1: The Cleaning and
Waterproof Coating of Masonry Buildings was written by Robert C
Mack, AlA. It inaugurated the Preservation Briefs series when
it was published in 1975.
The following historic preservation specialists provided technical
review of this publication: Frances Gale, Training Director,
National Center for Preservation Technology and Training,
National Park Service, Natchitoches, LA; Judith M. Jacob,
Architectural Conservator, Building Conservation Branch,
Northeast Cultural Resources Center, National Park Service, N.Y.,
NY; Robert M. Powers, Architectural Conservator, Powers and
Company, Inc., Philadelphia, PA; Antonio Aguilar, Kaaren Dodge,
JoEllen Hensley, Gary Sachau, John Sandor and Audrey T. Tepper,
Technical Preservation Services Branch, Heritage Preservation
Services Program, National Park Service, Washington, D.C; and
Kay D. Weeks, Heritage Preservation Services Program, National
Park Service, Washington, D.C.
This publication has been prepared pursuant to the National
Historic Preservation Act of 1966, as amended, which directs the
Secretary of the Interior to develop and make available information
concerning historic properties. Comments on the usefulness of
this publication may be directed to: Sharon C. Park, FAIA, Chief,
Technical Preservation Services Branch, Heritage Preservation
Services Program, National Park Service, 1849 C Street, N.W.,
Suite NC200, Washington, D.C 20240 (www2.cr.nps.gov/tps).
This publication is not copyrighted and can be reproduced without
penalty. Normal procedures for credit to the authors and the
National Park Service are appreciated.
Front Cover: Chemical cleaning of the brick and architectural terra
cotta frieze on the 1880s Pellsioll Buildillg, Washington, D.C. (now the
National Building Museulll), is showll here in progress. Photo:
Christina Henry.
Photographs llsed to illustrate this Brief were taken by Anne Grimmer unless
otherwise credited.
ISSN:0885-7016 November 2000
AttAchment e:
PreservAtion Brief 6 -
DAngers of ABrAsive cleAning to historic BuilDings
Mariners Medical arts
1901 Westcliff drive
neWport Beach, california
this PAge intentionAlly left BlAnk
6 PRESERV ATION
BRIEFS
Dangers of Abrasive Cleaning
to Historic Buildings
Anne E. Grimmer
U.S. Department of the Interior
National Park Service
Cultural Resources
Heritage Preservation Services
"The surface cleaning of structures shall be undertaken with the gentlest means possible. Sandblasting and other
cleaning methods that will damage the historic building materials shall not be undertaken."-The Secretary of the
Interior's "Standards for Historic Preservation Projects."
Abrasive cleaning methods are responsible for causing a great
deal of damage to historic building materials. To prevent
indiscriminate use of these potentially harmful techniques.
this brief has been prepared to explain abrasive cleaning
methods, how they can be physically and aesthetically de-
structive to historic building materials, and why they generally
are not acceptable preservation treatments for historic st ruc-
tures. There are alternative, less harsh means of cleaning and
removing paint and stains from historic buildings. However.
careful testing should preceed general cleaning to assure that
the method selected will not have an adverse effect on the
building materials. A historic building is irreplaceable. and
should be cleaned using only the "gentlest means possible"
to best preserve it.
What is Abrasive Cleaning?
Abrasive cleaning methods include all techniques that phys-
ically abrade the building surface to remove soils, discolor-
ations or coatings. Such techniques involve the use of certain
materials which impact or abrade the surface under pressure,
or abrasive tools and equipment. Sand, because it is readily
available, is probably the most commonly used type of grit
material. However, any of the following materials may be
substituted for sand, and all can be classified as abrasive
substances: ground slag or volcanic ash, crushed (pulverized)
walnut or almond shells. rice husks, gwund corncobs, ground
coconut shells, crushed eggshells, silica flour, synthetic par-
ticles, glass beads and micro-balloons. Even water under pres-
sure can be an abrasive substance. Tools and equipment that
are abrasive to historic building materials include wire
brushes, rotary wheels, power sanding disks and belt sanders.
The use of water in combination with grit may also be
classified as an abrasive cleaning method. Depending on the
manner in which it is applied, water may soften the impact
of the grit, but water that is too highly pressurized can be
very abrasive. There are basically two different methods
which can be referred to as "wet grit," and it is important to
differentiate between the two. One technique involves the
addition of a stream of water to a regular sandblasting nozzle.
This is done primarily to cut down dust. and has very little,
if any, effect on reducing the aggressiveness, or cutting action
of the grit particles. With the second technique, a very small
amount of grit is added to a pressurized water stream. This
method may be controlled by regulating the amount of grit
fed into the water stream, as well as the pressure of the water.
Why Are Abrasive Cleaning Methods Used?
Usually, an abrasive cleaning method is selected as an ex-
peditious means of quickly removing years of dirt accumu-
lation, unsightly stains, or deteriorating building fabric or
finishes, such as stucco or paint. The fact that sandblasting
is one of the best known and most readily available building
cleaning treatments is probably the major reason for its fre-
quent use.
Many mid-19th century brick buildings were painted im-
mediately or soon after completion to protect poor quality
brick or to imitate another material. such as stone. Sometimes
brick buildings were painted in an effort to produce what was
considered a more harmonious relationship between a build-
ing and its natural surroundings. By the 1870s, brick buildings
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402
Abrasively Cleaned vs. Untouched Brick. Two brick rowhouses with
a common far;ade provide an excellent point of comparison when only
one of the houses has been sandblasted. It is clear that abrasive blasting.
by removing the outer surface. has left the brickwork on the left rough
and pitted. while that on the right still exhibits an undamaged and
relatively smooth surface. Note that the abrasive cleaning has also
removed a considerable portion of the mortar from the joints of the
brick on the left side. which will require repointing.
were often left unpainted as mechanization in the brick in-
dustry brought a cheaper pressed brick and fashion decreed
a sudden preference for dark colors. However. it was still
customary to paint brick of poorer quality for the additional
protection the paint afforded.
It is a common 20th-century misconception that all historic
masonry buildings were initially unpainted. If the intent of
a modern restoration is to return a building to its original
appearance. removal of the paint not only may be historically
inaccurate, but also harmful. Many older buildings were
painted or stuccoed at some point to correct recurring main-
tenance problems caused by faulty construction techniques.
to hide alterations, or in an attempt to solve moisture prob-
lems. If this is the case. removal of paint or stucco may cause
these problems to reoccur.
Another reason for paint removal. particularly in rehabil-
itation projects. is to give the building a "new image" in
response to contemporary design trends and to attract inves-
tors or tenants. Thus. it is necessary to consider the purpose
of the intended cleaning. While it is clearly important to
remove unsightly stains. heavy encrustations of dirt. peeling
paint or other surface coatings. it may not be equally desirable
to remove paint from a building which originally was painted.
Many historic buildings which show only a slight amount of
soil or discoloration are much better left as they are. A thin
layer of soil is more often protective of the building fabric
than it is harmful. and seldom detracts from the building's
2
Abrading the Surface without Removing the Paint. Even though the
entire outer surface layer of the brick has been sandblasted off. spots
of paint still cling to the masonry. Sandblasting or other similarly
abrasive methods are not always a successful means of removing paint.
architectural and/or historic character. Too thorough cleaning
of a historic building may not only sacrifice some of the build-
ing's character, but also. misguided cleaning efforts can cause
a great deal of damage to historic building fabric. Unless
there are stains, graffiti or dirt and pollution deposits which
are destroying the building fabric. it is generally preferable
to do as little cleaning as possible. or to repaint where nec-
essary. It is important to remember that a historic building
does not have to look as if it were newly constructed to be
an attractive or successful restoration or rehabilitation proj-
ect. For a more thorough explanation of the philosophy of
cleaning historic buildings see Preservation Briefs: No. I
"The Cleaning and Waterproof Coating of Masonry Build-
ings," by Robert C. Mack. AlA.
Problems of Abrasive Cleaning
The crux of the problem is that abrasive cleaning is just that-
abrasive. An abrasively cleaned historic structure may be
physically as well as aesthetically damaged. Abrasive methods
"clean" by eroding dirt or paint, but at the same time they
also tend to erode the surface of the building material. In this
way, abrasive cleaning is destructive and causes irreversible
harm to the historic building fabric. If the fabric is brick,
abrasive methods remove the hard, outer protective surface,
and therefore make the brick more susceptible to rapid weath-
ering and deterioration. Grit blasting may also increase the
water permeability of a brick wall. The impact of the grit
particles tends to erode the bond beiween the mortar and the
brick, leaving cracks or enlarging existing cracks where water
can enter. Some types of stone develop a protective patina
or "quarry crust" parallel to the worked surface (created by
the movement of moisture towards the outer edge). which
also may be damaged by abrasive cleaning. The rate at which
the material subsequently weathers depends on the quality
of the inner surface that is exposed.
Abrasive cleaning can destroy. or substantially diminish.
decorative detailing on buildings such as a molded brickwork
or architectural terra-cotta. ornamental carving on wood or
stone. and evidence of historic craft techniques. such as tool
marks and other surface textures. In addition. perfectly sound
and/or "tooled" mortar joints can be worn away by abrasive
techniques. This not only results in the loss of historic craft
detailing but also requires repointing. a step involving con-
slderable time, skill and expense, and which might not have
been necessary had a gentler method been chosen. Erosion
and pitting of the building material by abrasive cleaning cre-
ates a greater surface area on which dirt and pollutants col-
lect. In this sense, the building fabric "attracts" more dirt,
and will require more frequent cleaning in the future.
In addition to causing physical and aesthetic harm to the
historic fabric, there are several adverse environmental ef-
fects of dry abrasive cleaning methods. Because of the friction
caused by the abrasive medium hitting the building fabric,
these techniques usually create a considerable amount of
dust, which is unhealthy, particularly to the operators of the
abrasive equipment. It further pollutes the environment
around the job site, and deposits dust on neighboring build-
ings, parked vehicles and nearby trees and shrubbery. Some
adjacent materials not intended for abrasive treatment such
as wood or glass, may also be damaged because the equipment
may be difficult to regulate.
Wet grit methods, while eliminating dust, deposit a messy
slurry on the ground or other objects surrounding the base
of the building. In colder climates where there is the threat
of frost , any wet cleaning process applied to historic masonry
structures must be done in warm weather, allowing ample
time for the wall to dry out thoroughly before cold weather
sets in. Water which remains and freezes in cracks and open-
ings of the masonry surface eventually may lead to spalling.
High-pressure wet cleaning may force an inordinate amount
of water into the walls, affecting interior materials such as
plaster or joist ends, as well as metal building components
within the walls.
Variable Factors
The greatest problem in developing practical guidelines for
cleaning any historic building is the large number of variable
and unpredictable factors involved. Because these variables
make each cleaning project unique, it is difficult to establish
specific standards at this time. This is particularly true of
abrasive cleaning methods because their inherent potential
for causing damage is multiplied by the following factors:
-the type and condition of the material being cleaned;
-the size and sharpness of the grit particles or the mechan-
ical equipment;
-the pressure with which the abrasive grit or equipment is
applied to the building surface;
-the skill and care of the operator; and
-the constancy of the pressure on all surfaces during the
cleaning process.
Micro-Abrasive Cleaning. This small. pencil-sized micro-abrasive unit
is used by some museum conservators to clean small objects. This
particular micro-abrasive unit is operated within the confines of a box
(approximately 2 cubic feet of space). but a similar and slightly larger
unit may be used for cleaning larger pieces of sculpture. or areas of
architectural detailing on a building. Even a pressure cleaning unit this
small is capable of eroding a surface. and must be carefully controlled.
"Line Drop." Even though the operator afthe sandblasting equipment
is standing on a ladder to reach the higher sections of the wall. it is still
almost impossible to have total control over the pressure. The pressure
of the sand hitting the lower portion of the wall will still be greater
than that above. because of the "lin e drop" in the distance from the
pressure source to the nozzle. (Hugh Miller)
Pressure: The damaging effects of most of the variable factors
involved in abrasive cleaning are self evident. However, the
matter of pressure requires further explanation. In cleaning
specifications, pressure is generally abbreviated as "psi"
(pounds per square inch), which technically refers to the "tip"
pressure, or the amount of pressure at the nozzle of the blast-
ing apparatus. Sometimes "psig," or pressure at the gauge
(which may be many feet away, at the other end of the hose),
is used in place of "psi." These terms are often incorrectly
used interchangeably.
Despite the apparent care taken by most architects and
building cleaning contractors to prepare specifications for
pressure cleaning which will not cause harm to the delicate
fabric of a historic building, it is very difficult to ensure that
the same amount of pressure is applied to all parts of the
building. For example, if the operator of the pressure equip-
ment stands on the ground while cleaning a two-story struc-
ture, the amount of force reaching the first story will be
greater than that hitting the second story, even if the operator
stands on scaffolding or in a cherry picker, because of the
"line drop" in the distance from the pressure source to the
nozzle. Although technically it may be possible to prepare
cleaning specifications with tight controls that would elimi-
nate all but a small margin of error, it may not be easy to
find professional cleaning firms willing to work under such
restrictive conditions. The fact is that many professional
building cleaning firms do not really understand the extreme
delicacy of historic building fabric, and how it differs from
modern construction materials. Consequently, they mily ac-
3
cept building cleaning projects for which they have no ex-
perience.
The amount of pressure used in any kind of cleaning treat-
ment which involves pressure, whether it is dry or wet grit,
chemicals or just plain water, is crucial to the outcome of the
cleaning project. Unfortunately, no standards have been es-
tablished for determining the correct pressure for cleaning
each of the many historic building materials which would not
cause harm. The considerable discrepancy between the way
the building cleaning industry and architectural conservators
define "high" and "low" pressure cleaning plays a significant
role in the difficulty of creating standards.
Nonhistoricllndustria/: A representative of the building clean-
ing industry might consider "high" pressure water cleaning
to he anything over 5,000 psi, or even as high as 10,000 to
15,000 psi' Water under this much pressure may be necessary
to clean industrial structures or machinery, but would destroy
most historic building materials. Industrial chemical cleaning
commonly utilizes pressures between I ,000 and 2,500 psi.
Spalling Brick, This soft. earlv 19th-cell/llry hrick was sandblasted ill
the 1960s; consequentlv. ~el'ere spallillg has resulted. Some hricks hal'l'
almo.1'I towlly disintegrated. and will el'enll/allv hUl'e to he replaced.
(Rohert S. Gamhle)
Historic: By contrast. conscientious dry or wet abrasive clean-
ing of a historic structure would be conducted within the
range of 20 to 100 psi at a range of 3 to 12 inches. Cleaning
al this low pressure requires the use of a very fine 00 or 0
mesh grit forced through a nozzle with a Y4 inch opening. A
similar. even more delicate method being adopted by archi-
tectural conservators uses a micro-abrasive grit on small,
hard-to-clean areas of carved, cut or molded ornament on a
building fac;ade. Originally developed by museum conserva-
tors for cleaning sculpture, this technique may employ glass
beads, micro-balloons, or another type of micro-abrasive
gently powered at approximately 40 psi by a very small, al-
most pencil-like pressure instrument. Although a slightly
larger pressure instrument may be used on historic buildings,
this technique still has limited practical applicability on a large
scale building cleaning project because of the cost and the
relatively few technicians competent to handle the task. In
general. architectural conservators have determined that only
through very com rolled conditions can most historic building
material be abrasivl:ly cleaned of soil or paint without meas-
urable damage to the surface or profile of the substrate.
Yet some professional cleaning companies which sepcialize
in cleaning historic masonry buildings use chemicals and water
at a pressure of approximately 1,500 psi, while other cleaning
firms recommend lower pressures ranging from 200 to 800 psi
for a similar project. An architectural conservator might de-
cide, after testing. that some historic structures could be
cleaned properly using a moderate pressure (200-600 psi), or
even a high pressure (600-1800 psi) water rinse. However,
4
cleaning historic buildings under such high pressure should
be considered an exception rather than the rule, and would
require very careful testing and supervision to assure that the
historic surface materials could withstand the pressure with-
out gouging, pitting or loosening.
These differences in the amount of pressure used by com-
mercial or industrial building cleaners and architectural con-
servators point to one of the main problems in using abrasive
means to clean historic buildings: misunderstanding of the
potentially fragile nature of historic building materials. There
is no one cleaning formula or pressure suitable for all situa-
tions. Decisions regarding the proper cleaning process for
historic structures can be made only after careful analysis of
the building fabric, and testing.
How Building Materials React to Abrasive Cleaning
Methods
Brick and Architectural Terra-Cotta: Abrasive blasting does
not affect all building materials to the same degrec. Such
techniques quite logically cause greater damage to softer and
more porous materials, such as brick or architectural terra-
cotta. When these materials are cleaned abrasively, the hard,
outer layer (closest to the heat of the kiln) is eroded, leaving
the soft. inner core exposed and susceptible to accelerated
weathering. Glazed architectural terra-cotta and ceramic ve-
neer have a baked-on glaze which is also easily damaged by
abrasive cleaning. Glazed architectual terra-cotta was de-
signed for easy maintenance, and generally can be cleaned
using detergent and water; but chemicals or steam may be
needed to remove more persistent stains. Large areas of brick
or architectural terra-cotta which have been painted are best
left painted. or repainted if necessary.
Plaster and Stucco: Plaster and stucco are types of masonry
finish materials that are softer than brick or terra-cotta: if
treated abrasively these materials will simply disintegrate.
Indeed. when plaster or stucco is treated abrasively it is usu-
ally with the intention of removing the plaster or stucco from
whatever base material or substrate it is covering. Obviously.
such abrasive techniques should not be applied to clean sound
plaster or stuccoed walls, or decorative plaster wall surfaces.
Building Stones: Building stones are cut from the three main
categories of natural rock: dense, igneous rock such as gran-
ite; sandy. sedimentary rock such as limestone or sandstone:
and crystalline, metamorphic rock such as marble. As op-
Abrasive Cleaning of Tooled Granite, Even this carefully colllrolled
"wet grit" blasting has erased verticallOoling marks in the CIII granite
blocks on the left. Not only has the lOoling been destroyed, bill the
damaged stone surface is now more susceptible 10 accelerated weath-
ering.
posed to kiln-dried masonry materials such as brick and ar-
chitectural terra-cotta, building stones are generally
homogeneous in character at the time of a building's con-
struction. However, as the stone is exposed to weathering
and environmental pollutants, the surface may become fria-
ble, or may develop a protective skin or patina. These outer
surfaces are very susceptible to damage by abrasive or im-
proper chemical cleaning.
Building stones are frequently cut into ashlar blocks or
"dressed" with tool marks that give the building surface a
specific texture and contribute to its historic character as
much as ornately carved decorative stonework. Such detailing
is easily damaged by abrasive cleaning techniques: the pattern
of tooling or cutting is erased, and the crisp lines of moldings
or carving are worn or pitted.
Occasionally, it may be possible to clean small areas of
rough-cut granite, limestone or sandstone having a heavy dirt
encrustation by using the "wet grit" method. whereby a small
amount of abrasive material is injected into a controlled.
pressurized water stream. However, this technique requires
very careful supervision in order to prevent damage to the
stone. Polished or honed marble or granite should never be
treated abrasively, as the abrasion would remove the fin ish
in much the way glass would be etched or "frosted" by such
a process. It is generally preferable to underclean . as too
strong a cleaning procedure will erode the stone, exposing
a new and increased surface area to collect atmospheric mois-
ture and dirt. Removing paint, stains or graffiti from most
types of stone may be accomplished by a chemical treatment
carefully selected to best handle the removal of the particular
type of paint or stain without damaging the stone. (See section
on the "Gentlest Means Possible")
Abrasive Cleaning of Wood. This wooden windowsill. molding and
paneling have been sandblasted to remove layers oj paint in the re-
habilitation oj this commercial building. Not only is some paint still
embedded in cracks and crevices oj the woodwork. but more impor-
tantly. grit blasting has actually eroded the summer wood. in eJJect
raising the grain. and resulting in a rough surJace.
Wood: Most types of wood used for buildings are soft. fibrous
and porous, and are particularly susceptible to damage by
abrasive cleaning. Because the summer wood between the
lines of the grain is softer than the grain itself, it will be worn
away by abrasive blasting or power tools, leaving an uneven
surface with the grain raised and often frayed or "fuzzy,"
Once this has occurred, it is almost impossible to achieve a
smooth surface again except by extensive hand sanding, which
is expensive and will quickly negate any costs saved earlier
by sandblasting. Such harsh cleaning treatment also obliter-
ates historic tool marks, fine carving and detailing, which
precludes its use on any interior or exterior woodwork which
has been hand planed, milled or carved.
Metals: Like stone, metals are another group of building
materials which vary considerably in hardness and durability.
Softer metals which are used architecturally. such as tin, zinc,
lead, copper or aluminum, generally should not be cleaned
abrasively as the process deforms and destroys the original
surface texture and appearance, as well as the acquired pa-
tina. Much applied architectural metal work used on historic
buildings-tin, zinc , lead and copper-is often quite thin and
soft, and therefore susceptible to denting and pitting. Gal-
vanized sheet metal is especially vulnerable, as abrasive treat-
ment would wear away the protective galvanized layer.
In the late 19th and early 20th centuries, these metals were
often cut, pressed or otherwise shaped from sheets of metal
into a wide variety of practical uses such as roofs, gutters and
flashing, and fac;ade ornamentation such as cornices. friezes.
dormers, panels, cupolas. oriel windows. etc. The architec-
ture of the 1920s and 1930s made use of metals such as
chrome, nickel alloys, aluminum and stainless steel in dec-
orative exterior panels, window frames. and doorways. Harsh
abrasive blasting would destroy the original surface finish of
most of these metals, and would increase the possiblity of
corrosion.
However, conservation specialists are now employing a
sensitive technique of glass bead peening to clean some of
the harder metals, in particular large bronze outdoor sculp-
ture. Very fine (75-125 micron) glass beads are used at a low
pressure of 60 to 80 psi. Because these glass beads are com-
pletely spherical, ther are no sharp edges to cut the surface
of the metal. After cleaning, these statues undergo a lengthy
process of polishing. Coatings are applied which protect the
surface from corrosion. but they must be renewed every 3 to
5 years. A similarly delicate cleaning technique employing
glass beads has been used in Europe to clean historic masonry
structures without causing damage. But at this time the proc-
ess has not been tested sufficiently in the United States to
recommend it as a building conservation measure.
Sometimes a very fine smooth sand is used at a low pressure
to clean or remove paint and corrosion from copper flashing
and other metal building components. Restoration architects
recently found that a mixture of crushed walnut shells and
copper slag at a pressure of approximately 200 psi was the
only way to remove corrosion successfully from a mid-19th
century terne-coated iron roof. Metal cleaned in this manner
must be painted immediately to prevent rapid recurrence of
corrosion. It is thought that these methods "work harden"
the surface by compressing the outer layer. and actually may
be good for the surface of the metal. But the extremely com-
plex nature and the time required by such processes make it
very expensive and impractical for large-scale use at this time.
Cast and wrought iron architectural elements may be gently
sandblasted or abrasively cleaned using a wire brush to re-
move layers of paint, rust and corrosion. Sandblasting was.
in fact, developed originally as an efficient maintenance pro-
cedure for engineering and industrial structures and heavy
machinery-iron and steel bridges, machine tool frames. en-
gine frames, and railroad rolling stock-in order to clean and
prepare them for repainting. Because iron is hard, its surface.
5
which is naturally somewhat uneven, will not be noticeably
damaged by controlled abrasion. Such treatment will. how'-
ever, re~ult in a small amount of pitting. But this slight abra-
sion creates a good surface for paint, since the iron must bc
repainted immediately to prevent corrosion. Any abrasive
cleaning of metal building components will also remove the
caulking from joints and around other openings. Such areas
must be recaulked quickly to prevent moisture from entering
and rusting the metal, or causing deterioration of other build-
ing fabric inside the structure.
When is Abrasive Cleaning Permissible?
For the most part, abrasive cleaning is destructive to historic
building materials. A limited number of special cases have
been explained when it may be appropriate, if supervised by
a skilled conservator, to use a delicate abrasive technique on
some historic building materials. The type of "wet grit" clean-
ing which involves a small amount of grit injected into a
stream of low pressure water may be used on small areas of
stone masonry (i.e., rough cut limestone, sandstone or un-
polished granite), where milder cleaning methods have not
been totally successful in removing harmful deposits of dirt
and pollutants. Such areas may include stone window sills,
the wps of cornices or column capitals, or other detailed areas
of the fa<;ade.
This is still an abrasive technique, and without proper cau-
tion in handling, it can be jus I as harmful 10 Ihe building
surface as any olher abrasive cleaning method. Thus, the de-
cision to use this type of "wet grit" process should be made
only after consultation with an experienced building con-
servator. Remember that il is very lime consuming and ex-
pensive to use any abrasive technique on a historic building
in such a manner that it does not cause harm to the often fragile
and friable building materials.
At this time , and only under certain circumstances, abrasive
cleaning methods may be used in the rehabilitation of interior
spaces of warehouse or industrial buildings for contemporary
uses.
Interior spaces of factories or warehouse structures in which
the masonry or plaster surfaces do not have significant design,
detailing, tooling or finish, and in which wooden architectural
features are not finished, molded, beaded or worked by hand,
may be cleaned abrasively in order to remove layers of paint
and industrial discolorations such as smoke, soot, etc. It is
expected after such treatment that brick surfaces will be rough
and pitted, and wood will be somewhat frayed or "fuzzy"
Permissible Abrasive Cleaning, In accordance with the Secretary of
the Interior's Guidelines for Rehabilitation Projects, it may be ac-
ceptable to use abrasive techniques to clean an industrial interior space
such as that il/ustraled here, because the masonry surfaces do not have
significant design, detailing, tooling or finish, and the wooden archi-
tectural features are not finished, molded, beaded or worked by hand.
6
with raised wood grain. These nonsignificant surfaces will be
damaged and have a roughened texture, but because they are
interior elements, they will not be subject to further deteri-
oration caused by weathering.
Historic Interiors that Should Not Be Cleaned Abrasively
Those instances (generally industrial and some commercial prop-
erties), when it may be acceptable to use an abrasive treatment
on the interior of historic structures have been described. But for
the majority of historic buildings, the Secretary of the Interior's
Guidelines for Rehabilitation do not recommend "changing the
texture of exposed wooden architectural features (induding struc-
tural members) and masonry surfaces through sandblasting or use
of other abrasive techniques to remove paint, discolorations and
plaster. ... "
Thus, it is not acceptable to clean abrasively interiors of
historic residential and commercial properties which have fin-
ished interior spaces featuring milled woodwork such as
doors, window and door moldings, wainscoting, stair balus-
trades and mantelpieces. Even the most modest historic house
interior, although it may not feature elaborate detailing, con-
tains plaster and woodwork that is architecturally significant
to the original design and function of the house. Abrasive
cleaning of such an interior would be destructive to the his-
toric integrity of the building.
Abrasive cleaning is also impractical. Rough surfaces of
abrasively cleaned wooden elements are hard to keep clean.
It is also difficult to seaL paint or maintain these surfaces
which can be splintery and a problem to the building's oc-
cupants. The force of abrasive blasting may cause grit par-
ticles to lodge in cracks of wooden elements, which will be
a nuisance as the grit is loosened by vibrations and gradually
sifts out. Removal of plaster will reduce the thermal and
insulating value of the walls. Interior brick is usually softer
than exterior brick, and generally of a poorer quality. Re-
moving surface plaster from such brick by abrasive means
often exposes gaping mortar joints and mismatched or re-
paired brickwork which was never intended to show. The
resulting bare brick wall may require repointing, often dif-
ficult to match. It also may be necessary to apply a transparent
surface coating (or sealer) in order to prevent the mortar and
brick from "dusting." However, a sealer may not only change
the color of the brick, but may also compound any existing
moisture problems by restricting the normal evaporation of
water vapor from the masonry surface.
"Gentlest Means Possible"
There are alternative means of removing dirt, stains and paint
from historic building surfaces that can be recommended as
more efficient and less destructive than abrasive techniques.
The "gentlest means possible" of removing dirt from a build-
ing surface can be achieved by using a low-pressure water
wash, scrubbing areas of more persistent grime with a natural
bristle (never metal) brush. Steam cleaning can also be used
effectively to clean some historic building fabric. Low-pres-
sure water or steam will soften the dirt and cause the deposits
to rise to the surface, where they can be washed away.
A third cleaning technique which may be recommended to
remove dirt, as well as stains, graffiti or paint, involves the
use of commerically available chemical cleaners or paint re-
movers, which, when applied to masonry, loosen or dissolve
the dirt or stains. These cleaning agents may be used in com-
bination with water or steam, followed by a clear water wash
to remove the residue of dirt and the chemical cleaners from
the masonry. A natural bristle brush may also facilitate this
type of chemically assisted cleaning, particularly in areas of
heavy dirt deposits or stains, and a wooden scraper can be
Do not Abrasively Clean these Interiors. Most historic residential and
some commercial interior spaces contain finished plaster and wooden
elements such as this stair balustrade and paneling which cOlltribwe
to the historic and architectural character of the structure. Such interiors
should not be subjected to abrasive techniques for the purpose of
removing paint, dirt, discoloration or plaster.
useful in removing thick encrustations of soot. A limewash
or absorbent talc, whiting or clay poultice with a solvent can
be used effectively to draw out salts or stains from the surface
of the selected areas of a building fa<;ade. It is almost im-
possible to remove paint from masonry surfaces without caus-
ing some damage to the masonry, and it is best to leave the
surfaces as they are or repaint them if necessary.
Some physicists are experimenting with the use of pulsed
laser beams and xenon flash lamps for cleaning historic ma-
sonry surfaces. At this time it is a slow, expensive cleaning
method, but its initial success indicates that it may have an
increasingly important role in the future.
There are many chemical paint removers which. when ap-
plied to painted wood, soften and dissolve the paint so that
it can be scraped off by hand. Peeling paint can be removed
from wood by hand scraping and sanding. Particularly thick
layers of paint may be softened with a heat gun or heat plate.
providing appropriate precautions are taken. and the paint
film scraped off by hand. Too much heat applied to the same
spot can burn the wood, and the fumes caused by burning
paint are dangerous to inhale, and can be explosive. Fur-
thermore. the hot air from heat guns can start fires in the
building cavity. Thus. adequate ventilation is important when
using a heat gun or heat plate. as well as when using a chem-
ical stripper. A torch or open flame should never be used.
Preparations for Cleaning: It cannot be overemphasized that
all of these cleaning methods must be approached with cau-
tion. When using any of these procedures which involve water
or other liquid cleaning agents on masonry, it is imperative
that all openings be tightly covered. and all cracks or joints
be well pointed in order to avoid the danger of water pen-
etrating the building's facade, a circumstance which might
result in serious moisture related problems such as efflores-
cence and/or subflorescence. Any time water is used on ma-
sonry as a cleaning agent, either in its pure state or in
combination with chemical cleaners. it is very important that
the work be done in warm weather when there is no danger
of frost for several months. Otherwise water which has pen-
etrated the masonry may freeze, eventually causing the sur-
face of the building to crack and spall, which may create
another conservation problem more serious to the health of
the building than dirt.
Each kind of masonry has a unique composition and reacts
differently with various chemical cleaning substances. Water
and/or chemicals may interact with minerals in stone and
cause new types of stains to leach out to the surface imme-
diately, or more gradually in a delayed reaction. What may
be a safe and effective cleaner for certain stain on one type
of stone, may leave unattractive discolorations on another
stone, or totally dissolve a third type.
Testing: Cleaning historic building materials. particularly
masonry, is a technically complex subject. and thus. should
never be done without expert consultation and testing. No
cleaning project should be undertaken without first applying
the intended cleaning agent to a representative test patch
area in an inconspicuous location on the building surface.
The test patch or patches should be allowed to weather for
a period of time, preferably through a complete seasonal
cycle, in order to determine that the cleaned area will not be
adversely affected by wet or freezing weather or any by-prod-
ucts of the cleaning process.
Mitigating the Effects of Abrasive Cleaning
There are certain restoration measures which can be adopted
to help preserve a historic building exterior which has been
damaged by abrasive methods. Wood that has been sand-
blasted will exhibit a frayed or "fuzzed" surface, or a harder
wood will have an exaggerated raised grain. The only way to
remove this rough surface or to smooth the grain is by la-
borious sanding. Sandblasted wood, unless it has been ex-
tensively sanded, serves as a dustcatcher, will weather faster,
and will present a continuing and ever worsening maintenance
problem. Such wood, after sanding. should be painted or
given a clear surface coating to protect the wood, and allow
for somewhat easier maintenance.
There are few successful preservative treatments that may
be applied to grit-blasted exterior masonry. Harder, denser
stone may have suffered only a loss of crisp edges or tool
marks, or other indications of craft technique. If the stone
has a compact and uniform composition, it should continue
to weather with little additional deterioration. But some types
of sandstone, marble and limestone will weather at an ac-
celerated rate once their protective "quarry crust" or patina
has been removed.
Softer types of masonry, particularly brick and architectural
terra-cotta, are the most likely to require some remedial treat-
ment if they have been abrasively cleaned. Old brick. being
essentially a soft, baked clay product. is greatly susceptible
to Increased deterioration when its hard. outer skin is re-
moved through abrasive techniques. This problem can be
minimized by painting the brick. An alternative is to treat it
with a clear sealer or surface coating but this will give the
masonry a glossy or shiny look. It is usuafly preferable to
paint the brick rather than to apply a transparent sealer since
7
Hazards of Sandblasting and Surface Coating. In order to "protect"
this heavily sandblasted brick, a clear surface coating or sealer was
applied. Because the air temperature was too cold at the time of ap·
plication, the sealer failed to dry properly, dripping in places. and
giving the brick surface a cloudy appearance.
sealers reduce the transpiration of moisture, allowing salts to
crystallize as subflorescence that eventually spalls the brick.
If a brick surface has been so extensively damaged by abrasive
cleaning and weathering that spalling has already begun. it
may be necessary to cover the walls with stucco. if it will
adhere.
Of course. the application of paint. a clear surface coating
(sealer). or stucco to deteriorating masonry means that the
historical appearance will be sacrificed in an attempt to con-
serve the historic building materials. However, the original
color and texture will have been changed already by the ab-
rasive treatment. At this point it is more important to try to
preserve the brick. and there is little choice but to protect it
from "dusting" or spalling too rapidly. As a last resort. in
the case of severely spalling brick. there may be no option
but to replace the brick-a difficult. expensive (particularly
if custom-made reproduction brick is used), and lengthy proc-
ess. As described earlier. sandblasted interior brick work.
while not subject to change of weather. may require the ap-
plication of a transparent surface coating or painting as a
maintenance procedure to contain loose mortar and brick
dust. (See Preservation Briefs: No. 1 for a more thorough
discussion of coatings.)
Metals, other than cast or wrought iron, that have been
pitted and dented by harsh abrasive blasting usually cannot
be smoothed out. Although fillers may be satisfactory for
smoothing a painted surface, exposed metal that has been
damaged usually will have to be replaced.
Selected Reading List
Ashurst. John. Cleaning Stone and Brick. Technical Pamphlet 4.
London: Society for the Protection of Ancient Buildings. IY77.
Asmus. John F. "Light Cleaning: Laser Technology for Surface Prep-
aration in the Arts." Technology and Conservation. 3: 3 (Fall
1978). pp. 14-18.
"The Bare-Brick Mistake." The Old House Journal. I: 2 (November
1973). p. 2
Brick Institute of America. Colorless Coatings for Brick Masonrl'.
Technical Notes on Brick Construction. Number 7E (September/
October 1976).
Gilder. Cornelia Brooke. Property OWller's Guide to the Maintenance
and Repair of Stone Buildings. Technical Series/ Nn. 5. Albany.
New York: The Preservation League of New York State. 1977.
Prudon. Theodore H.M. "The Case Against Removing Paint from
Brick Masonry." The Old HouseJournal. III : 2 (February 1975).
pp. fr-7
---"Removing Stains from Masonry." The Old House Journal.
V: 5 (May 1977). pp. 58-59.
Stambolov. T.. and J.R.J. Van Asperen de Boer. The Deterioration
and Conservation of Porous Building Materials in Monumellts:
A Review of the Literature. Second enlarged edition. Rome:
International Centre for Conservation. 1976.
8
Summary
Sandblasting or other abrasive methods of cleaning or paint
removal are by their nature destructive to historic building
materials and should not be used on historic buildings except
in a few well-monitored instances. There are exceptions when
certain types of abrasive cleaning may be permissible. but
only if conducted by a trained conservator, and if cleaning
is necessary for the preservation of the historic structure.
There is no one formula that will be suitable for cleaning
all historic building surfaces. Although there are many com-
merical cleaning products and methods available. it is im-
possible to state definitively which of these will be the most
effective without causing harm to the building fabric. It is
often difficult to identify ingredients or their proportions con-
tained in cleaning products; consequently it is hard to predict
how a product will react to the building materials to be
cleaned. Similar uncertanities affect the outcome of other
cleaning methods as they are applied to historic building
materials. Further advances in understanding the complex
nature of the many variables of the cleaning techniques may
someday provide a better and simpler solution to the prob-
lems. But until that time. the process of cleaning historic
buildings must be approached with caution through trial and
error.
It is important to remember that historic building materials
are neither indestructible. nor are they renewable. They must
be treated in a responsible manner. which may mean little
or no cleaning at all if they are to be preserved for future
generations to enjoy. If it is in the best interest of the building
to clean it, then it should be done "using the gentlest means
possible."
Weiss. Norman R. "Cleaning of Building Exteriors: Problems anu
Procedures of Dirt Removal." Technolo?.\' and COllSen'atioll.
2176 (Fall 1976). pp. 8-13.
---Exterior Cleaning of Historic Masollr.\' Buildings. Draft. Wash-
ington. D.C.: Office of Archeology and Historic Preservation.
Heritage Conservation and Recreation Service. U.S. Depart·
ment of the Interior. 1976.
This Preservation Brief was writlen hy Anne E. Grimmer. Architectural Hi,·
torian. Technical Preservation Services Division. Valuahle suggestions and
comments were made hy Hugh C. Miller. AlA. Washington. D.C.: Marlin E.
Weaver. Otlawa. Ontario. Canada: Terry Bryant. Downers Grove. IIlinoi"
Daniel C. Cammer. McLean. Virginia: and the professional staff of Technical
Preservation Services Division. Dehorah Cooney edited the final manuscript.
The illustrations for this brief not sRf'cifically credited are from the fi les of the
Technical Preservation Services Division.
This publication was prepared pursuant to Executive Order 11593. "Protection
and Enhancement of the Cultural Environment." which directs the Secretary
of the Interior to "develop and make available to Federal agencies and State
and local governments information concerning professional methods and tech-
niques for preserving, improving, restoring and maintaining historic proper-
ties." The Brief has been developed under the technical editorship of Lee H.
Nelson, AlA, Chief, Preservation Assistance Division, National Park Service,
U.S. Department of the Interior, Washington, D.C. 20240. Comments on the
usefulness of this information are welcome and can be sent to Mr. Nelson at
the above address. This publication is not copyrighted and can be reproduced
without penalty. Normal procedures for credit to the author and the National
Park Service are appreciated. June 1979.