Ahwahnee_HSR_1.2011_pgs_265-300.pdf

Recommendations: Material ConservationARCHITECTURAL RESOURCES GROUP

Histor ic Structures Report

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January 2011

Exterior Log Construction Log construction at Th e Ahwahnee includes structural timber framing systems at the Porte Cochere and covered entrance walkway (see Exterior Replacement and Substitute Materials), veneer coverings of structural steel columns at the Dining Room and south wing suites, balcony railings throughout the hotel, and siding above the windows of the Dining Room.

Mechanisms of Deterioration Most wood deterioration is the result of moisture penetration.

Water entering through the end grain of a log is drawn by capillarity through the wood cells, leading to rot deep within the wood structure. Wood that is wet will swell and shrink, causing cracks, splits, and checks that threaten structural strength. Wet wood is also vulnerable to fungal attack and rotting, as well as insect infestation.

Intense UV radiation from sunlight damages wood surfaces and intensifi es moisture and thermal cycling. In addition, wood architectural elements can be attractive avian habitats.

Existing Conditions Log column covers at the south wing suites have large bore holes from woodpecker activity. Log column covers and siding at the Dining Room are in good condition overall, with localized areas of degraded fi nishes at the base of columns due to abrasion or excessive moisture. Concrete pads at these locations are deteriorating, and they should be repaired to prevent moisture intrusion at the base of columns. Balcony railings are in poor condition, exhibiting widespread rotting and repair failures that contribute to unstable and hazardous conditions.

Recommended Treatments High priority should be given to balcony railing repairs. Rotted wood needs to be replaced, either by selective patching repairs or by replacing the entire component. Repair methods include plastic patches, where moldable fi llers such as epoxy or putty are placed in voids, or Dutchman repairs where material loss is replaced with wood cut to size. Plastic repairs may be strengthened with non-corroding rods or plates inserted into logs. Repair methodologies depend on the function of the wood component (e.g., structural elements vs. trim) and the extent of damage. If a wood component is to be repaired, all rotten material must be removed and the exposed surfaces treated with a fungicide/insecticide wood preservative. Both plastic patches and Dutchman repairs must fi t tightly to the existing wood to prevent moisture intrusion and further rotting of the wood. Repairs and replacement components should match the profi le, texture, and color of the historic fabric; ideally Dutchman repairs and replacement elements should be the same wood species as the material being repaired.

Th e ultimate cause of the woodpecker activity at the south wing suites needs to be identifi ed to choose appropriate solutions. Woodpeckers attack architectural woodwork for three main reasons: foraging for food, marking territory to attract a mate (drumming), and building a nest (roosting). Foraging activity may be eliminated by removing the food source; injecting an insecticide wood preservative directly into insect galleries and holes created by the birds should kill the insects feeding on the wood (injection ports should be sealed to prevent bird ingestion of the insecticide). Drumming usually does not cause signifi cant damage and is diffi cult to prevent. Roosting damage may be minimized by providing alternative housing; installing bird boxes on the columns should encourage woodpeckers to roost in the boxes rather than the logs.

Wood rot at the base of logs may be prevented by minimizing the exposure of log bases to water. Site grading must drain water away from the building. Concrete pads used to elevate structural log columns should be repaired and maintained.

Log timber framing needs to be inspected regularly to detect deterioration or failure of steel fastening systems. At the Porte Cochere, safety measures (such as signage) should be implemented to prevent tall vehicles from colliding with the framing.

Insecticides and wood preservatives can be used to address active insect infestations and dry rot and to prevent future damage.

Preferred treatments include mixtures of disodium octaborate

Figure 435: Mortar exhibits vertical cracking and detachment from stones in isolated areas, 2009.

(Source: ARG)

Figure 436: Recently replaced mortar does not match the historic masonry, 2009.

(Source: ARG)

ARCHITECTURAL RESOURCES GROUP Recommendations: Material Conservation

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January 2011 tetrahydrate, commonly known as borates. Borates combat both fungal rot and insect infestation, and they have the advantage of being water-borne and non-toxic to humans.

Proper application and maintenance of coatings is essential to protecting the wood features from weathering and infestation. Paint and stain keep moisture from penetrating wood, and they mitigate the damaging eff ects of the sun’s rays. Possible historic wood coatings include penetrating oils, clear coatings, semi-transparent or opaque stains, and paint. Wood fi nish sequences should be identifi ed by collecting and examining samples of historic wood so that appropriate coatings may be specifi ed for maintenance and repair work, particularly for unpainted logs.

Figure 439: Log column covers at the south wing suites exhibit damage from woodpecker activity, 2009. (Source: ARG)

Figure 437: Exterior log construction includes column covers, window framing, siding, and raft er tails, 2009. (Source: ARG)

Figure 438: Poorly executed repairs are failing at this log balcony railing, 2009.

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January 2011

Recommended Treatments Detaching door components can be repaired by gluing and clamping the doors, and installing concealed dowels or splines to reinforce existing mortise and tenon joints. Unstable wood fi ller patches should be replaced with Dutchman repairs, particularly at door latches. Dutchman repairs should also be carried out to fi ll voids where original hardware was removed and not replaced. Proper application and maintenance of coatings is essential to protecting the wood and metal features from weathering. Paint and stain prevent metal corrosion, keep moisture and insects from penetrating wood, and mitigate the damaging eff ects of the sun’s rays. Historic paint colors should be identifi ed by collecting and examining samples from historic doors.

Figure 440: Several doors have had their swing direction reversed, exposing the raised-grain texture to weathering, 2009. Coordinator strips have been removed, and steel bracket reinforcement has been added. (Source: ARG)

Figure 441: Th is “kalamein” door is dented and hardware has been removed, 2009. (Source: ARG)

Figure 442: Stiles at the base of these doors are split, and paint is failing from poor surface preparation, 2009. (Source: ARG)

Exterior Wood and Metal Doors Historic doors at Th e Ahwahnee are primarily wood stile and rail, with a few board doors, some Dutch doors, and metal-clad “kalamein” doors at utility and service areas. Doors in public areas, as well as suites and parlor rooms, are designed to bring the outdoors in with multi-light glazing in operable as well as fi xed leafs. Th e swing directions of several doors have been reversed to facilitate circulation and egress, resulting in the exposure of rough-grain fi nishes (originally installed on interior door faces) to exterior weathering.

Mechanisms of Deterioration As described in the previous section, wood deterioration stems from moisture penetration, insect infestation, and UV radiation, all of which are exacerbated by the failure of protective paint or stain coatings. Additional damage is infl icted by abrasion, impacts, and vibrations stemming from heavy use by the public and hotel staff .

Moisture infi ltration typically leads to warping, localized rot, and loss of wood surfaces, while mechanical damage results in nicks and scratches, loose or missing hardware, and detached or split components including stiles, rails, and glazing mullions.

Metal-clad doors are susceptible to corrosion and deformation of the sheet metal that can impede door operation.

Existing Conditions Doors are generally in fair to good condition, but the reversed doors do not operate smoothly. Th e removal of wood strip coordinators impedes proper closure, placing stress on stile and rail components that are detaching from one another. Other doors show similar deterioration and have been reinforced using steel brackets and guy wires. Replacement of original hardware has resulted in weakened areas that were left unfi lled or have unstable wood fi ller patches.

Metal-clad doors are in good condition, with minor corrosion. Doors and frames exhibit isolated coatings failure manifested as blistering and peeling of paint layers.

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Wood and Steel Windows Historic wood and steel windows remain in place at the ground and sixth fl oors. Confi gurations include fi xed multi-light units at the Dining Room, stained glass and transom windows at the Great Lounge, leaded casements at the sixth fl oor Library, wood hopper windows at the Kitchen, and steel casements at the exit stair and Service Yard. Original wood shutters are evident throughout the hotel, and historic wood siding is in place below windows at the Dining Room and Solarium.

Mechanisms of Deterioration Wood windows are vulnerable to deterioration caused by weathering and moisture intrusion. Coatings and glazing putty that fail from UV radiation expose wood elements to moisture from precipitation as well as failed waterproofi ng systems such as sealants, fl ashing and gutters. Water penetration of the wood results in rot and deformation including swelling, cracking and warping. Steel windows also deteriorate from water intrusion, which results in corrosion of the metal accompanied by dimensional changes that can damage adjacent glass and masonry materials.

Existing Conditions Paint failure is observed on vulnerable areas such as the bottom rails of windows, particularly at south and west facing facades. Wood deterioration includes split wood components, raised grain, and failed wood fi ller patches. Wood shutters exhibit faded paint coatings and localized soiling at the top. Stained and leaded glass at the Great Lounge exhibits deformation of the lead cames and chemical degradation of the glass. At the sixth fl oor, wood frames are warped, lead cames are deformed and panes are broken (a detailed analysis of leaded glass can be found in Appendix D).

Recommended Treatments Proper application and maintenance of coatings is essential to protecting the wood features from weathering and infestation. Paint and stain keep moisture from penetrating wood, and mitigate the damaging eff ects of the sun’s rays. Maintenance of coatings is also essential for steel windows to prevent corrosion. An important

Figure 445: Leaded glass windows at the sixth fl oor have failing paint and glazing putty, 2009. (Source: ARG)

Figure 444: Historic wood window at the Great Lounge, with stained glass insert, 2009. (Source: ARG) component of coatings maintenance is periodic gentle cleaning, which loosens dirt deposits and biological growth that retain moisture and degrade coatings. Finish sequences should be identifi ed by collecting and examining samples from historic windows, so that appropriate colors and coatings may be specifi ed for maintenance and repair work.

Splits and loss of wood materials can be repaired using epoxy fi llers.

Severe rot or material loss can be remedied with Dutchman repairs.

Loose or missing glazing putty should be replaced in kind to prevent moisture intrusion. Leaded and stained glass should be repaired by a qualifi ed conservator.

Figure 443: Steel casement windows at the stair tower (center) are original, 2009.

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January 2011

Exterior Ornamental Metal Light fi xtures at the ground fl oor and south wing suites range from large pendant fi xtures suspended from loggia soffi ts to smaller lanterns hanging from granite piers, false beam ends, and log column covers. Some fi xtures may be replicas that were fabricated during the 1977 renovation (as called for in specifi cations). Th e fi xtures exhibit a variety of forms, but all appear to be an unknown metal (probably copper, iron or bronze) with a protective coating of white metal (such as zinc). Some of the mounting hardware appears to be iron. Glass panes are clear or amber. All fi xtures are painted brown or red; some coatings appear to have been recently renewed.

Mechanisms of Deterioration Metals have diff erent reactions to environmental weathering; air and water exposure results in the creation of both protective layers and corrosion. Copper forms a protective patina in contact with air, resulting in a green surface deposit that may or may not be aesthetically desirable. Zinc reacts in a similar way, at fi rst forming a zinc oxide “white rust” that combines with carbon dioxide in the air to form a protective zinc carbonate layer. In iron and steel, the presence of water and oxygen creates an electrolytic cell that promotes continual corrosion through oxidation; therefore, ferrous (iron-containing) metals require protective coatings to prevent corrosion. Zinc is applied as a metallic coating to protect both ferrous metals and cuprous (copper-containing) metals in a variety of applications including, galvanizing, plating, spraying, and painting.

Existing Conditions Overall the light fi xtures are in fair condition, exhibiting paint failure throughout as well as isolated metal deformation, exposed wiring, loose or missing components, and loose or cracked glazing. Ferrous corrosion was observed in mounting hardware. See the Historic Lighting Fixture Condition Assessment in Th e Ahwahnee Historic Furnishings Report for more information on the light fi xtures.

Recommended Treatments Proper application and maintenance of coatings is essential to protecting the metal features from weathering and corrosion.

Historic paint colors should be identifi ed by collecting and examining samples from historic fi xtures. Fixtures with loose or exposed wiring should be repaired to conform to code. While the light fi xtures are architectural decoration, these movable objects can also be considered part of historic museum collections, and original fi xtures should be identifi ed, cataloged, assessed, and conserved.

Figure 446: Red paint on this pendant fi xture appears to be recently renewed, 2009. (Source:

ARG)

Figure 447: Paint coatings on this fi xture are failing, 2009. (Source: ARG)

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January 2011

Figure 448: Original wood guest room windows have been replaced with sliding aluminum windows, 2009. (Source: ARG)

Figure 450: Resin raft er tail covers appear to be performing well, but exhibit circular stains where fastening dowels were placed, 2009.

(Source: ARG)

Figure 449: Resin beam appears to be performing well, 2009. (Source: ARG)

Exterior Replacement and Substitute Materials A variety of new materials are present in Th e Ahwahnee that are either replacement in-kind of original materials, or diff erent materials substituted for the original. Features replaced in kind include the log construction of the Porte Cochere and covered entrance walkway including wood siding and decorative paint, several ground fl oor doors (although with changes to design), all slate roof shingles, and copper sheet-metal gutters, downspouts, and fl ashing.

Substitute materials include all but a few of the wood guest room windows, which have been replaced with aluminum sliding windows.

At the Service Yard, standing-seam copper roofi ng was substituted for slate roofi ng. A number of projecting features originally constructed of stained concrete and wood, including raft er tails and false beam ends, have been replicated using molded fi berglass reinforced polyester resin covers placed over the original materials.

Mechanisms of Deterioration Log Construction and Wood Siding: As described in previous sections, primary deterioration mechanisms for wood elements include moisture intrusion, insect infestation, and UV radiation.

Wood Doors As described previously, wood doors are susceptible to deterioration from moisture intrusion, insect infestation, UV radiation, and impacts and vibration from operation.

Slate Shingles Slate shingles are more or less vulnerable to weathering depending on the structure of the clay minerals making up the parent rock, and the presence of minerals that oxidize or solubilize when exposed to atmospheric conditions. Th e strength of the rock determines how thin or thick a shingle should be split. Slates with high water absorption are vulnerable to damage from freeze-thaw cycling, which causes expansion and scaling. Metallic sulfi de minerals in slate can oxidize and expand, causing cracking, splitting, and spalling.

Carbonate minerals in slate can undergo chemical changes where they become soluble and volumetrically larger, resulting in holes or breakage of slates. Slate shingles can be damaged by improper installation methods, and are vulnerable in service to impact damage from falling objects.

Copper Copper corrodes as it reacts with air, resulting in surface deposits of oxidized materials that form a patina. Patina can be an aesthetically desirable characteristic, and it also forms a protective layer. Like all metals, copper carries an electromotive potential that governs the migration of metallic ions from one metal to another in the presence of an electrolyte. Where dissimilar metals are in contact a process known as galvanic corrosion occurs, where one metal corrodes preferentially. Galvanic corrosion occurs among commonly used metals including iron, steel, copper, brass, bronze, and zinc. Where dissimilar metals such as copper and iron are used together in construction, they should be isolated from one another by gaskets, sealants, or coatings. Copper is a relatively soft and ductile metal;

depending on the alloy composition, copper roofi ng elements will be more or less vulnerable to deformation from impacts and falling objects. Gutters can be clogged by tree debris, increasing weight loads, facilitating freeze-thaw damage from expanding ice, and leading to leaks that damage adjacent building components.

Aluminum Windows Aluminum corrodes in atmospheric conditions to form aluminum oxide, which forms a protective layer that slows further corrosion.

However, the aluminum oxide layer becomes ineff ective in low pH (acidic) and high pH (alkaline) solutions. Aluminum has a high thermal conductance, requiring that window assemblies be constructed with suffi cient insulation systems to avoid excessive heat gain and prevent condensation in cold environments. Aluminum windows are factory-coated with specialized paints, making it diffi cult to re-paint them once the coating fades, is damaged, or otherwise fails.

Fiberglass Reinforced Polyester Resin Covers Selected projecting elements including raft er tails and false beam ends were covered with molded sleeves made from polyester resin reinforced with fi berglass. Specifi cations from the 1977 work identify

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Dion Fr 6604-T polyester resin and Owens-Corning fi berglass to be mixed with integral color and formed around metal armatures.

Th e covers were installed by covering the concrete elements with epoxy, drilling holes for dowels with which the covers were fastened.

Synthetic materials such as epoxy and polyester resin that are formed from organic compounds are vulnerable to degradation from UV radiation resulting in surface fading and fraying, as well as cracking of the material.

Existing Conditions In general, replacement and substitute features are in good condition because they were installed relatively recently.

Log Construction and Wood Siding Timber framing systems at the Porte Cochere and covered entrance walkway, including steel connection plates and bolts, were reconstructed in 1988 and are in good condition, with localized wearing of wood fi nishes. However, abraded coatings on the underside of beams spanning the driveway are an indication that impacts from tall vehicles are a potential source of damage to structural integrity. Th e covered entrance walkway structure and decorative paint schemes are well-protected and in good condition, with isolated loss of fi nishes and abraded wood at display cases.

Slate Shingles Slate shingles exhibit limited chipping, breakage, and detachment, particularly in areas where ice and snow fall from one roof to another.

Copper Copper roofi ng materials are generally in good condition. Th ere is a signifi cant accumulation of duff in gutters, which tends to clog downspouts and is a fi re hazard in hot, dry weather. Gutters exhibit isolated deformation from falling objects, vehicle impacts, and ladders leaned against them.

Aluminum Windows Aluminum windows throughout are in good condition with isolated instances of weather stripping detachment.

Fiberglass Reinforced Polyester Resin Covers Th ese replacement features are generally performing well, with limited surface fading and cracking of false beam ends. Raft er tail covers exhibit discoloration at dowel placement locations. Some cracks on the false beam ends appear to have been fi lled with a material that is darker than the faded surface.

Recommended Treatments Log Construction and Wood Siding Log timber framing needs to be inspected regularly to detect deterioration or failure of steel fastening systems. At the Porte Cochere, safety measures (such as signage) should be implemented to prevent tall vehicles from colliding with the framing. Protective coatings should be maintained to minimize damage from moisture and UV radiation. Damage to decorated siding at the covered entrance walkway should be repaired using compatible wood fi llers, stains, paints, and clear coatings.

Slate Shingles An annual inspection and maintenance program should include the replacement of detached and split slates, and slates that exhibit more than 50% surface scaling or more than 25% loss of material.

Copper Inspection and maintenance routines should include checking for gaps, detachment and breakage at solder joints and sealant joints in gutters and fl ashing. Protect gutters and downspouts from vehicular impacts. Keep gutters clean and free of debris, but do not lean ladders against them for access.

Aluminum Windows As stated elsewhere in this document, the aluminum windows are inappropriate with regard to Th e Ahwahnee’s original design and it is recommended that they be removed and replaced with windows that more accurately refl ect the historic appearance of the hotel. Interim maintenance actions include inspection of sealant joints at window perimeters and replacing detached weather stripping.

Figure 452: Abrasion damage at underside of Porte Cochere, 2009. (Source: ARG)

Figure 451: A small percentage of replacement slates are chipped or broken, 2009. (Source:

ARG)

Figure 453: Duff collects on roofs and in copper gutters, 2009. (Source: ARG)

Fiberglass Reinforced Polyester Resin Covers Regularly inspect these elements for tight fi t, and material degradation such as cracks, fading, or fraying. It is essential to confi rm the specifi c product used to manufacture these features in order to identify appropriate maintenance and repair techniques. Use repair methods and materials specifi c to the formulation of the synthetic material; oft en, proprietary materials are available with manufacturer’s instructions on how to conduct repairs.

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Figure 454: Th e integrally colored of the guest room plaster walls and ceilings shown in this photograph has been covered with fl at paint, c. 1943. (Source: Yosemite National Park Museum, 113940)

Figure 455: Buckling plaster and blistering paint are evidence of moisture penetration at this guest room hallway ceiling, 2009. (Source: ARG)

Interior Plaster Plaster walls and ceilings of Th e Ahwahnee interior are character-defi ning features. Original specifi cations call for three-coat plaster applied over expanded metal lath at the ceilings and over the gypsum block at the walls. Th e specifi cations allowed for a variety of fi nish coat materials and textures to be specifi ed later such as the textured plaster used in the Great Lounge and Registration Lobby. Th ree-coat plaster systems impart qualities of texture and depth that are largely absent from modern wall fi nishing systems. Th e plasticity of the material allows for subtle surface profi le variations to achieve a rustic appearance; the bulk and density of the system contribute to qualities of sound absorption and thermal insulation; and fi nish coats can be created in a range of textures for visual and tactile eff ects.

Plaster is typically coated with opaque or semitransparent coatings, but can also be formulated with added pigments as an integral color fi nish, achieving a deep, rich tone that cannot be replicated with surface coatings. Th e color was mixed with the top layer of the three-coat plaster system. Integrally colored plaster was popular in the 1920s when Th e Ahwahnee was built. Sampling of original materials has located historic integrally colored plaster at the walls of two guest rooms and at the original sixth fl oor ceiling. Based on this evidence and historical photographs, it appears that integrally colored plaster was used extensively throughout the main building including: all guest rooms, guest bathrooms, all public rooms and hallways. Th e integral color has more depth of color than a painted surface, which creates a soft er, more rustic feel.

Mechanisms of Deterioration Original specifi cations identify gypsum plaster as the predominant material for interior wall fi nishing. Gypsum is sensitive to high moisture environments and is therefore not used in exterior applications or wet settings. For spaces such as bathrooms, kitchens, showers, and restrooms, the specifi cations call for wainscots rendered in Portland cement plaster or Keene’s cement. Keene’s cement is made from gypsum burned at a higher temperature and is less sensitive to water. Nevertheless, all plaster is porous and is thus susceptible to moisture penetration that corrodes underlying expanded metal lath.

Corrosion of the lath causes dimensional changes in the metal that lead to cracks in plaster, as well as detachment of the lath manifested as buckling or deformation of the plaster. Severe water damage breaks down the plaster, resulting in disaggregation or powdering of the plaster. Plaster is a brittle material, and will crack when subject to other types of movement such as diff erential settling or seismic events.

Some of the cracking in the plaster may be from the original construction of the building. Because of the tight construction schedule, the building was enclosed and heated quickly, making the plaster and concrete dry and cure too quickly, resulting in cracks.

Existing Conditions Most interior plaster walls and ceilings exhibit minor to moderate cracking from building movement, concentrated at stress points at the ceilings near concrete beams. Water intrusion from plumbing leaks is fairly common on ceilings in guest room hallways. Isolated ceiling paint blistering can be a sign of minor leaks from roofs, plumbing, wall openings, or poor surface preparation prior to painting.

Th e integral color of the plaster is no longer evident because the plaster is now painted throughout the building. Th is has changed the character and appearance of the plaster.

Th ere are several areas of patched plaster throughout the hotel, most notably in the ceilings. Some areas of patches are poorly executed and very visible. See the room by room recommendations for more information on locations of these patches.

Recommended Treatments Buckled and powdery plaster is indicative of severe water damage to lath and attachment systems. Th e source of moisture intrusion should be identifi ed and corrected. While buckled plaster may be re-attached if the lath is intact, dis-aggregated plaster should be removed and the lath and plaster replaced. Cracked plaster should be repaired by cutting or routing out the cracks to provide suffi cient keying for the

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January 2011 patch. Patching materials for cracks and replacement of damaged plaster should be physically and visually compatible with the historic material, and fi nished to match the surrounding profi le and texture of the historic plaster. Where decorative fi nishes such as stenciling are present, care should be taken to paint the patch to match the surrounding decorative scheme or in the case of hairline cracking in decorative fi nishes, it may be advisable to leave the area unrepaired.

A comprehensive survey needs to be conducted to identify the locations and design of original integral color plaster walls and ceilings. Based on samples collected from the hotel, the presence of integral color plaster fi nishes appears to be widespread. Evidence of this potentially signifi cant design feature has been obscured over time by multiple paint layers, and further investigation is needed to identify what could be original fi nishes. Samples should be collected from representative areas of Th e Ahwahnee, and analyzed to determine fi nish histories and historic colors, textures, and materials.

Figure 456: Much of the interior plaster has an uneven, rustic texture, 2009. (Source: ARG)

Figure 457: Plaster walls exhibit cracks from building movement at stress points such as room corners, 2009. (Source: ARG)

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Interior Decorative Painting Decorative paint schemes, from geometric stencils and paintings to faux-wood treatments and painted color accents, are present throughout the hotel. Original stenciling is evident in most guest rooms, part of the Great Lounge, and in isolated hallway locations. Stencils and painting have been decoratively overpainted (presumably using the same or similar colors and patterns) in the Great Lounge, guest room hallways, Registration Lobby, and Gift Shop. Current decorative schemes in the guest room elevator lobbies are substantially diff erent from earlier historic designs. Historic decorative painting has been obliterated by plain paint layers at the Great Lounge, guest room walls around connecting doors, and the columns of the Registration Lobby. A project is currently in development to identify, assess and conserve original decorative painting in Th e Ahwahnee main building.

Mechanisms of Deterioration Paint layers can be disrupted by damage occurring to substrates such as cracks, detachment and spalling of underlying plaster and concrete. Adhesive properties of paint may be compromised by inadequate surface preparation, and cohesive properties are aff ected by the ratio of binder, vehicle and pigment components. Moisture infi ltration can result in swelling, detachment, disintegration, and fl aking of paint layers. Protective clear coats can be subject to yellowing or discoloration. Surface soiling obscures design elements and the perception of original colors.

Existing Conditions Original stencil designs are soiled and exhibit cracks and spalls related to the deterioration of plaster and concrete substrates. Th e condition of original decorative schemes that have been overpainted is unknown.

Recommended Treatments Further investigation is recommended to identify original designs, colors, and paint materials including binders and pigments. Specifi c paint formulations convey information about the fi nal appearance of the decorations, especially regarding color saturation, transparency, texture and gloss. Modern emulsion paints used in overpainting have a tendency to be opaque and glossy, lending a “plastic” appearance to decorative painting that originally may have had a more subtle visual texture.

An interior paint analysis project currently under development will expose original designs in the Great Lounge and in guest room connecting walls and elevator lobbies, and identify historic paint colors. Following paint analysis, conservation recommendations include cleaning original stenciling in guest rooms and hallways, and restoring original colors in the Registration Lobby and Great Lounge. Investigation, conservation, and documentation of original decorative painting needs to be carried out by a qualifi ed conservator with experience in the conservation of wall paintings.

Figure 459: In the guest rooms, stencil designs have been re-worked or recreated (left ) to blend in with original work (right), 2009. (Source: ARG)

Figure 458: Stenciling has been extensively re-worked in guest room hallways with only a few vestiges of original work, such as this design on the fourth fl oor, 2009. (Source: ARG)

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Figure 461: Decorative painting at a guest room connecting door, 1943. Decorative schemes at these locations have been covered with solid color paint and are no longer visible.

(Source: Yosemite National Park Museum, 113950)

Figure 460: Historical decorative paint scheme at a guest room elevator lobby in 1943, which has since been painted over with a diff erent design. (Source: Yosemite National Park, 113947)

Figure 463: Paint failure at decorative stenciling resulting from moisture damage to plaster and concrete substrates, 2009. (Source: ARG)

Figure 462: Cracks in concrete at typical stress points damage stenciling in guest rooms and hallways, III-46

January 2011

Interior Stone Stone is used sparingly in the interior as granite column covers in the Dining Room as well as green jasper stone masonry of the Elevator Lobby fi replace and stairway, and the Solarium fountain. Th e mortar of the granite and jasper masonry is light red.

Mechanisms of Deterioration Th e granite and jasper stones chosen for these applications are very durable materials. While interior stone masonry is not exposed to weathering, it is susceptible to damage from building movement. In addition, the jasper stone fi replace and fountain undergo stresses related to their functions. At the Elevator Lobby fi replace, burning wood exposes the jasper stone surround to high temperatures and leaves soot deposits that stain the masonry. Th e jasper stone masonry of the Solarium is constantly exposed to water that can promote biological growth and carry soluble minerals that leave deposits on stones, both of which potentially disrupt stone and mortar. Moisture can also penetrate mortar joints and cause cracking, detaching, and effl orescence.

Existing Conditions Th e granite column covers of the Dining Room are in good condition, with light soiling. Th e jasper stone masonry at the Elevator Lobby stairway is in good condition.

Th e jasper stone fi replace surround at the Elevator Lobby has deposits of soot that detract from its appearance, but otherwise it is in good condition. Th e jasper stone was cleaned sometime aft er 1980 and a glossy clear coating was applied to the stone and mortar. Th e jasper stone basin of the Solarium fountain has heavy biological growth (moss), dark staining on the rock fountain, and effl orescence on basin stones and mortar. All of the jasper stone masonry has a clear glossy coating.

Recommended Treatments Th e granite column covers in the Dining Room may be gently cleaned with a vacuum. Removal of soot stains from the jasper stone fi replace should be undertaken by a qualifi ed conservator using the gentlest means possible. It is not necessary to remove all patina from the stone, but only excess build up. Th e high gloss coating should be researched and/or tested to determine what was used. If it is possible to remove the coating without damaging the historic stone and mortar, then it should be removed. If removal is not feasible, or the removal would cause damage to the historic materials, then the coating should be left in place.

Th e jasper stone fountain should be evaluated with the goal of minimizing moisture damage. Th e basin should be drained in order to inspect the concrete liner for damage and leaks, and identify appropriate waterproofi ng measures to prevent moisture penetration through the stone masonry of the basin. Th e water source for the fountain should be analyzed to determine whether the water contains minerals that cause the dark staining and effl orescence. It may be necessary to fi lter the water to minimize deposition of soluble minerals. Biological growth should be removed from the fountain, and steps to prevent further biological growth should be investigated.

Adding chemicals be added to fountain water is not recommended because the chemicals may damage the stone or mortar; it may be possible to retard biological growth by other means. Removal of crusts of effl orescence from the fountain may be diffi cult; tests should be conducted by a qualifi ed conservator.

Figure 464: Granite column covers in the Dining Room are in good condition, 2009. (Source: ARG)

Figure 467: Th e jasper stone masonry of the Solarium fountain exhibits deterioration related to its function as a water feature, 2009. (Source: ARG)

Figure 466: Th e jasper stone fi replace in the Elevator Lobby is stained from soot deposits. Note high gloss coat over stone and mortar, 2009. (Source: ARG)

Figure 465: Photograph of jasper stone fi replace in the Elevator Lobby, 1980.

(Source: Charles Cramer, courtesy Yosemite National Park Research Library)

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Figure 470: Interior stained concrete fl oors are cracked and faded, 2009. (Source: ARG)

Figure 468: Cast-stone fi replace surrounds are stained and soiled, 2009. (Source: ARG)

Interior Concrete and Cast Stone Concrete is used on the interior to form the scored and stained fl oors of many of the ground fl oor public rooms and the North Mezzanine Lounge; back-of-house fl oors are painted concrete.

Cast stone is used at fi replace surrounds and hearths. Cast stone is a highly refi ned form of concrete used widely in the late 19th and early 20th centuries. Individual units are molded and cast using a variety of aggregates, cements, and mineral coloring agents that are carefully selected, graded, and proportioned to resemble stone. Cast stone gained popularity in architecture because ornamental pieces can be mass-produced at a lower cost than in carved natural stone.

Mechanisms of Deterioration Interior concrete and cast-stone masonry are not subject to weathering stresses, but they are nonetheless vulnerable to cracking and detachment from building movement, and to moisture penetration from leaks that mobilizes soluble salts and corrodes underlying reinforcing metal, leading to cracks, spalls, and staining.

Concrete fl oors are exposed to wear and abrasion from foot traffi c, as well as increased UV radiation near south and west facing windows.

Cast-stone fi replace elements are subject to specifi c deterioration relating to wood combustion, such as high temperatures and soot deposits.

Existing Conditions Stained concrete fl oors exhibit narrow cracks throughout, though this condition was observed soon aft er the concrete was poured.

Th e green and red stain applied to these fl oors is also severely faded, probably the result of abrasion from foot traffi c, but the durability of the stains could also have been aff ected by the alkaline concrete material or exposure to increased UV radiation near windows.

Cast-stone masonry fi replace surrounds and hearths are discolored and stained by soot deposits, and isolated areas of mortar cracking and detachment were observed. Drop-shaped light-colored staining on the Great Lounge and Winter Club Room fi replace surrounds suggest that the cast-stone surface fi nish is soluble by some liquid that was spilled on them.

Th e cast stone at the Tudor Lounge and Tresidder Room fi replaces was painted sometime aft er 1997. Non-historic stencils were added to the surrounds

Recommended Treatments Cracks on the stained concrete fl oors do not appear to be active, and are not a threat to the preservation of these interior features; therefore patching is not necessary. It is not recommended that stains or pigments be applied directly to the faded concrete surface. To restore the faded stain, a reversible approach is preferred. A successful system might entail the application of a protective barrier coat, followed by a color coat such as tinted wax, then a protective traffi c coat. Th is multi-coat system might also reduce the visibility of concrete cracks.

Minor mortar deterioration in cast-stone masonry should be repaired by removing cracked and detached mortar and replacing it with a physically and visually compatible mortar matching the historic material in hardness, color, texture, and profi le. Removal of soot staining from cast-stone fi replace surrounds should be carried out by a qualifi ed conservator who can identify the gentlest materials and techniques possible. Discolored fi replace surrounds at the Great Lounge and Winter Club Room should be evaluated by a qualifi ed conservator, who can identify the existing surface fi nish, visually integrate the stains, and apply a compatible protective coating.

Consult with a conservator to test methods for removing the paint from the cast stone at the Tudor Lounge and Tresidder Room fi replaces. If the paint can be removed without damaging the cast stone, then remove the paint. If paint removal would cause extensive damage to the cast stone, then repaint to the historic color of the cast stone.

Figure 469: Painted cast-stone fi replace surround at Tudor Lounge, 2009. (Source: ARG)

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January 2011

Interior Wood Interior wood architectural features include log column covers and exposed log ceiling framing in the Dining Room, painted doors and windows throughout, stained and painted trim throughout, paneling in the Mural Room and Library, fl oors in the Great Lounge and Mural Room, and secondary elements such as stair railings, fi replace mantels, and radiator covers.

Doors and trim elements in many of the public spaces were treated to raise the wood grain for aesthetic eff ect. Where door swings have been reversed, these raised grain surfaces now face the exterior of the building.

Historical photographs indicate that guest room wood features such as doors, windows, trim, and baseboards were initially dark in color, suggesting that they were either stained and varnished or painted with dark color paint.

Mechanisms of Deterioration Th e primary deterioration mechanism for wood is moisture. Interior wood is subject to water penetration from roof leaks, plumbing leaks, and fl ooding. Rot stemming from moisture penetration makes wood vulnerable to insect infestation. Doors and windows are subject to damage from heavy use and abrasion from furniture moving. Wood fl oors are vulnerable to wear and abrasion from foot traffi c and furniture moving. Repeated refi nishing of fl oor clear coatings can result in signifi cant loss of material over time, reducing the life of wood fl oors.

Damage to interior wood may also be infl icted by inappropriate surface treatments, including penetrating oils such as tung oil or linseed oil. Linseed oil oxidizes and polymerizes as it is exposed to air, hardening inside wood cells to a relatively insoluble material. As multiple coats are applied over time, a sticky buildup of oils is formed which attracts and retains dirt.

Existing Conditions Log construction is in good condition, with minor surface soiling.

Doors, windows and trim generally show moderate wear and abrasion from use and are in fair to good condition. Stained and varnished paneling in the Library is in good condition. Th e Great Lounge fl oor is in good condition but protective fi nishes are uneven and missing in areas, possibly due to the repositioning or removal of carpets from the room over time. Th e Mural Room fl oor exhibits overall wearing of fi nishes.

Th e Mural Room paneling shows moderate wear at the lower part of the wall from recurring activities such as incidental visitor abrasion, furniture moving, and fl oor cleaning. Degradation of stain and varnish is observed adjacent to the steam radiator, suggesting that the fi nishes are being damaged by thermal and moisture cycling concentrated in that area. Overall, the paneling appears to have been refi nished, possibly with a lighter-colored stain than the original.

Th e refi nishing process was probably carried out with the intent of unifying the appearance of worn or discolored paneling, and likely entailed the application of stain directly over the existing varnish followed by a clear coating.

Wood doors, frames and trim, particularly guest room doors and egress doors, show impact damage from luggage carts, cleaning carts, furniture moving, and habitual use of deadbolts to prop doors open. Paint layers on guest room doors are blistering and peeling, indicating improper surface preparation.

Recommended Treatments Dusty log trusses and purlins in the Dining Room should be cleaned using a vacuum; if necessary, gentle aqueous methods (water and mild detergent) can be used to remove stubborn dirt and grime, being sure to wipe wood surfaces dry immediately. Damaged or worn paint fi nishes on doors, windows and trim should be repaired by spot-painting to avoid excessive buildup of paint layers.

Figure 471: Floor fi nishes in the Great Lounge are in good condition, but the area under the center rug is unfi nished, 2007. (Source: ARG)

Figure 472: Th is 1943 historical photograph of room 223 shows guest room baseboards that are darker than they are currently. (Source: Yosemite National Park, 113954)

Figure 473: Guest room doors exhibit paint blistering and peeling, 2009. (Source: ARG)

III-49

January 2011

Wood fl oors need periodic renewal of protective coatings to prevent wear and minimize potential water damage to boards. Current industry standards emphasize the use of polyurethane coatings, but maintenance of these coatings requires relatively frequent sanding (particularly if clear coats and stain are allowed to wear completely off ) that can signifi cantly reduce the thickness of wood fl oors over time. To preserve the maximum amount of original fabric, it is recommended that wax coatings be applied to protect wood fl oors. Wax coatings may be maintained without removing historic materials, because it can be stripped using steam.

Avoid the use of penetrating oils including linseed oil on unfi nished wood, and avoid the buildup of stains, clear coats or other non-reversible fi nishes on paneling. To refresh unfi nished or stained interior wood, reversible treatments such as wax coatings are preferred; wax may also be tinted and applied to stained surfaces to unify discolored paneling. Over time, wax coatings may be removed with steam without harming historic fi nishes. Damaged areas of paneling should be repaired by spot-application of stain matching the color of the historic fabric, followed by a compatible clear coating.

A fi nishes survey and analysis should be conducted to understand the original fi nishes applied to the guest room woodwork. Th e information gleaned from the fi nishes analysis can be used in future rehabilitation or restoration eff orts, particularly when the level of paint buildup on guest room doors will require stripping them of paint before they can be re-painted.

Figure 474: Th e Mural Room wood fl oor fi nishes are worn, and the paneling appears to have been refi nished, 2009. (Source: ARG)

III-50

January 2011

Interior Brick Brick used on the interior is mainly fi re brick used to build fi reboxes and surrounds in the hotel fi replaces. Fire brick is a class of refractory brick formulated and heated to withstand high temperature applications.

A condition assessment of fi replaces in Th e Ahwahnee, including evaluation of fi rebox conditions and recommendations for repair, was conducted for DNC by CCS-Canaday Enterprises Incorporated in May 2008.

Mechanisms of Deterioration Th ough designed to withstand high temperatures, fi rebrick is more or less durable depending on the specifi c formulation of aluminosilicates used in manufacturing. Firebricks in wood-burning fi replaces are subject to high temperatures, abrasion, ash and slag that can break down the clay body of bricks. When the brick is heated, it is more brittle and can break more easily. Currently, then the hotel staff make the fi res, they push the wood and ashes against the back wall, which is causing additional damage to the brick.

Th e brick surround at the Colonial Room fi replace sometime aft er 1997. Th is paint coating may trap moisture and might cause deterioration of the brick.

Existing Conditions Fire bricks in fi replace fi reboxes show material degradation throughout the hotel, in the form of material loss and friability of bricks. Fire bricks are also stained by soot deposits from wood fi res.

At the Colonial Room fi replace, the paint on the fi re surround is bubbling and fl acking off at the lower portion of the fi replace and is chipped around the fi rebox opening.

Recommended Treatments As recommended by the CCS-Canaday report, deteriorated fi re bricks in fi reboxes should be replaced. Replacement bricks should match the historic fi re brick in color and texture, but may be selected to be more durable than the historic fabric. Reducing or eliminating wood fi res in fi replaces will mitigate deterioration. Th e use of metal fi re backs may also reduce deterioration of fi re bricks, but they are not historically accurate. In the large fi replaces, where there is suffi cient room, the burning logs should be placed out from the back wall to protect the wall.

Consult with a conservator to test methods for removing the paint from the brick at the Colonial Room fi replace. If the paint can be removed without damaging the brick, then remove the paint. If paint removal would cause extensive damage to the brick, then repaint to the historic color of the brick.

Figure 475: Bricks making up fi reboxes in the fi replaces are damaged from long exposure to high temperatures, 2009.