Design Guidelines for the West Chester Historic District, Borough of West Chester, Pennsylvania

B. GUIDELINES TO PRESERVE AND PROTECT HISTORIC BUILDINGS

1. Cleaning Historic Structures
Exterior cleaning of historic structures should be done in the gentlest way possible. Destructive techniques such as sandblasting and harsh chemical cleaners are not recommended. High-pressure washing is not appropriate and can cause damage to structures (Figure 35).

Recommended Cleaning Techniques

Exterior Woodwork (in preparation for repainting)
Apply 1:4 solution of household chlorine bleach in water to soiled woodwork, using a natural or plastic-fiber bristle brush or garden bug sprayer. Scrub using natural or plastic-fiber bristle brush, followed by a water rinse at a maximum of 1,200 pounds per square inch (psi) of pressure at 24 inches from the wall surface using a 15 degree spray tip.

Brick, stone, and stucco
Water rinse using maximum 600 psi water pressure at 6 inches from masonry surface using a 15 degree spray tip (or 1,200 psi at 24 inches). For heavily soiled surfaces, apply a dilute mixture of a specially formulated masonry cleaner according to the manufacturer’s instructions. After the specified contact time, scrub masonry using natural or plastic-bristle brush, followed by maximum 600 psi water rinse. Never use muriatic acid on historic brick masonry. Do not use acidic or caustic cleaners that will etch glass, damage paint finishes, or pose environmental risks.

2. Historic Masonry

2.1 Repointing.
Historic masonry requires particular maintenance to be preserved. Although brick units themselves have a long life, mortar joints deteriorate over time and require periodic renewal. Where repointing is required, care should be taken to ensure that the brick is not damaged in the process of removing deteriorated pointing. The new mortar should match the color, texture, and tooling of the original mortar, not the appearance of the surface dirt on weathered pointing (Figure 36). Unless the existing joint profile is a scribed profile, the new pointing should be slightly recessed, struck flat. Deeply struck (recessed) and concave joint profiles are generally not appropriate. The slight recess is important, however, to prevent the mortar from smearing onto the face of the bricks, resulting in an enlarged joint width which is both unsightly and historically inappropriate. New pointing should not have a high Portland cement content. Mortars rich in Portland cement are harder and less permeable than historic masonry units, causing damage to the brick or stone. Recommended historic mortars for historic West Chester masonry include the following:

Historic Wall Brick:
1 part by volume white Portland cement
2 parts by volume hydrated lime
6 parts by volume selected sand.

Historic Chimney Brick:
1 part by volume white Portland cement
1 part by volume hydrated lime
5 parts by volume selected sand

2.2 Paint Removal.
Generally, the complete removal of paint from historic masonry is not appropriate. If, during a restoration project, an owner desires to remove paint from brick walls, a spot test should be conducted to assess the condition of the original brickwork below. If the building has been painted for several decades, an owner may elect to repaint the structure. Prior to undertaking paint-stripping operations, a test panel must be conducted to make sure the brickwork is not damaged during the cleaning process. Dry-grit blast cleaning (sandblasting) is never recommended, because it causes irreversible damage to historic masonry surfaces.

3. Stucco (Cement/Lime Plaster)
Stucco should not be applied over historic materials. The removal of stucco to expose original historic masonry is acceptable. However, some stone structures were originally roughly laid and covered with a cement/lime plaster. In this case, the cement/lime plaster should not be removed, but rather preserved or restored. A test panel should be prepared to determine the feasibility and appropriateness of removing exterior stucco. Great care should be taken in removing stucco so as not to damage the historic fabric.

3.1 Simulated Brick and Stone Facings.
Simulated brick and stone facings have been applied to a small number of brick buildings in the Historic District. Typically these Portland cement plaster facings were applied when aggressive salesmen convinced building owners that the cost of the facing would be less than the cost of repointing and maintaining a brick facade over time. Existing facings should be maintained and painted brick red. Where the facing is deteriorated, a test panel should be prepared to determine the feasibility and appropriateness of removing it. Because of the strong adhesion of the Portland cement, removing the facing may not be economically feasible. Great care should be taken in removing the simulated brick facing so as not to damage the historic brick substrate.

4. Exterior Colors and Color Schemes
Exterior colors and color schemes should be appropriate to the architectural style and period of the building. Paint analysis and historic documentation are encouraged for the owner who desires specific color information about a historic structure, but it is not mandatory. Certain paint manufacturers offer historically accurate exterior paint colors, including specific palettes for different architectural styles. Refer to the bibliography (appendix E) for published references relating to appropriate historic colors and color schemes.

In most cases, color schemes can be organized according to the body, major trim, minor trim, and shutter colors (Figure 37). The body color covers wall surfaces, and on commercial buildings includes any storefront piers. In some cases, the body color will be natural brick or stone and will not require painting. Major trim includes the cornice, window frames, decorative window crowns, storefront cornices, storefront columns, and bulkheads. Minor trim consists of window sashes, doors, and storefront frames. Shutters are typically painted yet another color.

While early nineteenth-century buildings historically featured simple color schemes – brick walls, white exterior woodwork, and dark green shutters and front door, for example – later Victorian styles featured color schemes which might include several colors. However, overly elaborate color schemes, and all color schemes employing multiple pastel colors, are not appropriate. The so-called “painted ladies” are based on popular images of Victorian architecture, not on history.
When a historic building is repainted, the removal of all paint layers to bare wood is not recommended. Except for heavily weathered paint, scraping off loose material in preparation for new coats of paint is sufficient. Unpainted brick surfaces generally should not be painted. Painted brick surfaces should remain painted. In some instances, paint may be removed from brick, but typically it is not recommended (See B.2.2 - Paint Removal).

On commercial buildings, the paint scheme for the entire building should be coordinated, including building cornice, upper-floor windows and shutters, storefront, and doors. Storefronts should not be repainted without taking into account the color scheme and condition of paint on the entire facade. Finally, historically unpainted metals, such as brass storefront framing or hardware, should not be painted.

5. Historic Roofing Systems
Significant historic roofing materials and features that are visible from the street should be preserved. Efforts should be made to retain and repair original roofing that is visible from the street. Where the material is too deteriorated and replacement is necessary, new roofing materials should replicate the original roofing material used on the historic building. Building owners are encouraged to conduct an investigation to determine the original roofing materials, either by means of looking at historical photographs or by physical examination of the roof sheathing by a knowledgeable roofer. Typical historic roofing used on sloping roofs in the West Chester Historic District was standing-seam metal or slate shingles.

Flat roofs are not addressed in these Design Guidelines, and no Certificate of Appropriateness is required to obtain a building permit for the replacement of a flat roof.

5.1 Slate Shingle Roofing.
Slate shingle roofing replaced wood shingle roofing in large cities because slate was fireproof. In rural areas, slate shingle roofing was also desired for its durability, and in the late nineteenth century for its decorative qualities (Figure 38).

The continued maintenance of existing slate roofing is highly encouraged and less expensive than replacement with a substitute material. The replacement of severely deteriorated historic slate roofing with new slate roofing is also highly encouraged. On buildings with Mansart roofs, the replacement of slate with standard asphalt shingles is not appropriate (Figure 39). On buildings with gable or hipped roofs, replacement of slate with asphalt shingles is discouraged but acceptable (See B.5.4 - Asphalt Shingles).

5.2 Metal Roofing.
The continued maintenance of existing metal roofing is highly encouraged. The replacement of severely deteriorated metal roofing with new metal roofing is also highly encouraged. Traditional standing-seam metal roofing, painted, is encouraged for re-roofing projects and new roofs (Figure 40). However, pre-formed standing-seam roofing which utilizes low profile (1 inch height) seams may also be acceptable.

5.3 Substitute Materials.
Substitute materials that closely replicate historic roofing are acceptable. For example, recycled rubber/polymer shingles or fiber-reinforced cement shingles that resemble slate cost less than a natural slate roof but visually simulate slate.

5.4 Asphalt Shingles.
Asphalt shingle roofing is not recommended on roof slopes that are visible. If asphalt shingles are proposed for a visible roof, it is recommended that the shingles be heavyweight, dimensional shingles that resemble historic materials. A color similar to the historic roofing material is recommended. White and light green asphalt shingle roofing, for example, cannot be appropriate, because slate in these colors is not found in nature.

The prominence of the roof and the height and angle of the roof as seen by a pedestrian will be factors that the HARB will consider in its evaluation of each individual roof replacement proposal (Figure 41). The roofing material used on a sloping porch roof or storefront cornice is near to the viewer and, therefore, visually very important. In contrast, a shallow pitch, say 3-in-12 slope, gable roof on a three-story commercial building is simply not visible from the sidewalk and, therefore, not visually important. However, on a building with a Mansart roof, as much as one-third of the visible face of the building is the roofing material. To replace the slate shingles on a Mansart roof with asphalt shingles would be analogous to replacing a brick facade with vinyl siding.

5.5 Gutters and Downspouts.
When hung gutters and downspouts are replaced, the use of half-round gutters and smooth round downspouts is historically appropriate and thus recommended for historic buildings (Figure 42). New copper, terne-coated stainless steel, and lead-coated copper gutters and downspouts may be allowed to weather naturally, but aluminum and galvanized steel gutters, downspouts, and leader boxes should be painted to blend in with the color of the building to reduce their visibility. Vinyl gutters and downspouts are not appropriate.

Built-in gutters and pole gutters (water diverters) are often found on historic buildings (Figure 43). These forms of gutters collect roof water without the visual intrusion of an exposed metal gutter at the cornice line. The continued maintenance of built-in gutters and pole gutters is highly encouraged. The in-kind replacement of severely deteriorated built-in gutters and pole gutters is also highly encouraged.

6. Preserving Historic Roof Features
Significant historic roof features such as cornices, cupolas, and dormers should be preserved or restored (See Figure 39). Removing or obscuring any of these features is not appropriate.

6.1 Chimneys.
Historic chimneys are significant features of a structure’s architectural character. A replacement chimney should be an accurate reproduction of an original chimney and based on physical or pictorial evidence (Figure 44). Where an interior chimney is removed as part of a proposed alteration, the exterior portion of the chimney should be preserved or reconstructed to retain the historical appearance of the structure. (Caution: if the interior chimney has been removed, the chimney above the roof must be properly braced to support the imposed load!)

6.2 Dormers and Cupolas.
Examples of significant historic gable, hipped, segmental arch-head, and shed dormers exist in the West Chester Historic District (Figure 45). The construction of new dormers or a cupola on any principal facade is not appropriate. If physical and pictorial evidence proves that either of these features originally existed, the reconstruction of the original feature is encouraged. New dormers are permissible only on secondary facades. New shed, gable, and segmental-arch dormers should be compatible in size, scale, and proportion with the original facade, and their placement should relate vertically to the building’s fenestration (Figure 46). The overall width of dormers should be no wider than one-half the overall roof width (Figure 47).

6.3 Skylights.
The installation of skylights on a principal facade is not appropriate. Skylights may be installed on secondary facades. Skylights should be low-profile, flat-glazed construction, and mounted close to the roof. Careful consideration should be given to the placement of skylights. Skylights should relate vertically to the overall fenestration of the facade (Figure 48).

7. Mechanical, Electrical, and Communications Equipment
The installation of television antennas, security cameras, satellite dishes, outdoor air-conditioning equipment, exhaust fans, and other mechanical, electrical, and communications equipments on principal facades is not appropriate. Equipment should be situated so it is not readily visible from a public way. Air-conditioning equipment may not be mounted on sloping roofs. On flat roofs, air-conditioning equipment should be screened from view by vertical board or other acceptable screening.

8. Wall Siding and Trim
While most buildings in the West Chester Historic District are brick masonry, some additions and out-buildings are wood-frame construction. Siding should be appropriate to the building. In West Chester, wood siding is typically horizontal clapboarding (Figure 49), either a beveled profile or a drop-siding profile (“German siding”). The visual character created by the texture and pattern of historic siding should not be altered by its replacement with different siding profiles or non-historic siding materials. In the Historic District, vinyl and aluminum siding are not appropriate substitute materials except on secondary facades. The removal of existing synthetic siding and its replacement with historically appropriate siding is encouraged. Wood trim elements such as corner boards, window and door surrounds, brackets, moldings, and other decorative features should also be repaired or replaced to match their historic appearance.

The cladding (wrapping) of exterior woodwork such as cornices, corner boards, fascias, projecting bays, brackets, window and door frames, porch framing and trim, and other exterior woodwork with aluminum or vinyl materials is not appropriate. Not only does the cladding cover historic wood moldings and architectural detail, but it also causes the covered woodwork to deteriorate because of moisture that becomes entrapped under the sheet metal.