Windows & Siding

Cladding & Siding

Historic cladding materials are highly visible and significant features of a building's exterior. Different materials such as clapboard, shingles, pressed metal, stucco and tile were used in various historic periods, and in many cases relate specifically to a particular style. Therefore, preservation and repair of historic sheathing materials is important to maintain the character of historic buildings. Periodic inspections should be made to assess the condition of the cladding, and any necessary repairs undertaken immediately.

This can prevent any damage or deterioration from becoming widespread, and save money in the long run. Any work should be carefully planned to have the least physical impact on cladding materials. Any cleaning should be undertaken using careful, non-abrasive techniques. High pressure blasting using either water or abrasives can be very damaging to historic materials, and should not be used. If the cladding material requires painting or caulking, this treatment will serve as its primary weather shield. Painted surfaces should be well maintained. As with all historic material, damaged sections should be replaced in-kind to match the historic in all visual and physical qualities.

Synthetic Siding Materials

The installation of vinyl or aluminum siding materials over historic cladding or replacement of historic materials with vinyl or aluminum is not an appropriate preservation treatment. Synthetic materials seriously alter the historic appearance and character of a building in many ways including the width of the siding often does not match clapboard width, shadow reveals are reduced, and trim is frequently changed or removed at cornices, corners, windows and doors. Historic surface treatments such as decorative shingles or verge boards, as well as other materials and patterns, may be completely obscured or destroyed.

Moreover, synthetic siding has the potential to cause serious long term damage to the building. There are also serious technical and maintenance issues to consider. Foremost among these is the accelerated deterioration of structural elements from moisture trapped unnoticed behind the new siding. This moisture can drastically decrease the efficiency of insulation. Related interior consequences include peeling paint, wallpaper, and cracked wall surfaces.

Siding materials are also problematic because repair will almost always be noticeable-the colors can fade over time and products may be changed or discontinued. When properly maintained, historic cladding materials such as clapboard and shingles are durable and serviceable; their existence on thousands of historic structures after decades of service is proof that they are economic and long-term alternatives. Their repair is strongly recommended.


Historic windows are among the most important features in defining a building's character, and proper treatment is extremely important. Frequent maintenance now can prevent expensive headaches later: historic windows should be periodically inspected and properly maintained. A painted wood window relies on its paint for weather protection. Without paint, the extremes of heat, cold, sunlight and moisture can quickly act on the exterior frame and sash, damaging the wood. Therefore inspection of the windows along with appropriate scraping, priming and painting should be foremost in any maintenance plan.

If inspection of window unit reveals repairable damage or deterioration, existing window sash and frames should be retained and repaired rather than replaced whenever possible. Unlike modern metal replacement windows, historic wood units were constructed so that damaged portions could be repaired or replaced one part at a time. The damaged portion of a window component should be replaced with material matching the original. This approach results in cost savings for the building owner. Replacement of an entire window unit is appropriate only when it is deteriorated beyond repair.

The new windows should match the originals in material, finish, configuration, setback, profiles and all other visual and reflective qualities. Historic metal sash windows are likewise important features that should be retained and repaired of possible. Steel and metal windows have their own sets of problems and treatments, but specific guidance is available through our office. In buildings such as historic factory complexes, rows of large historic windows contribute to exterior character and should be repaired and retained.