Detail of restored roof; Link to Parknet
<photo> detail of historic windows

Identify    Protect    Repair    Replace    Remove   Re-Create

Identify, Retain and Preserve

Identifying, retaining, and preserving windows--and their functional and decorative features--from the restoration period. Such features can include frames, sash, muntins, glazing, sills, heads, hoodmolds, panelled or decorated jambs and moldings, and interior and exterior shutters and blinds.

photos of the 18th century Ephrata Cloister, in Lancaster, PA, with its distinctive multi-paned windows

The Ephrata Cloister, founded in 1732 by German settlers, is located in Central Pennsylvania's Lancaster County. One of America's earliest religious communities, its twelve buildings are open to the public and interpreted. The distinctive multi-paned windows shown here from the interior (see photo, right) are part of the visitor's experience at this National Historic Landmark site. Photo left: Courtesy, Pennsylvania Historical and Museum Commission; Photo right: NPS files.

Conducting an indepth survey of the condition of existing windows from the restoration period early in the planning process so that repair and upgrading methods and possible replacement options can be fully explored.

Not Recommended
Altering windows or window features from the restoration period.

Failing to properly document window features from the restoration period which may result in their loss.Applying paint or other coatings to window features or removing them if such treatments cannot be documented to the restoration period.

Changing the type or color of protective surface coatings on window features unless the work can be substantiated by historical documentation.

Stripping windows of sound material such as wood, cast iron, and bronze.

Replacing windows from the restoration period solely because of peeling paint, broken glass, stuck sash, and high air infiltration. These conditions, in themselves, are no indication that windows are beyond repair.

Protect and Maintain

Protecting and maintaining the wood and architectural metals from the restoration period which comprise the window frame, sash, muntins, and surrounds through appropriate surface treatments such as cleaning, rust removal, limited paint removal, and re-application of protective coating systems.

photo of well maintained window that is 250 years old

In spite of the fact that this historic window is 250 years old, routine maintenance of the paint coupled with glazing putty repairs have kept the sash in operable condition over the years. Photo: © John Leeke.

Making windows weathertight by re-caulking, and replacing or installing weatherstripping. These actions also improve thermal efficiency.

Evaluating the existing condition of materials to determine whether more than protection and maintenance are required, i.e. if repairs to windows and window features will be required

Not Recommended
Failing to provide adequate protection of materials on a cyclical basis so that deterioration of the window results.

Retrofitting or replacing windows from the restoration period rather than maintaining the sash, frame, and glazing.

Failing to undertake adequate measures to assure the protection of window materials from the restoration period.


Repairing window frames and sash from the restoration period by patching, splicing, consolidating or otherwise reinforcing. Such repair may also include replacement in kind--or with compatible substitute material--of those extensively deteriorated or missing parts when there are surviving prototypes such as architraves, hoodmolds, sash, sills, and interior or exterior shutters and blinds. The new work should be unobtrusively dated to guide future research and treatment.

photo of original leaded glass windows during Restoration in a conservation studio

Original leaded glass windows are repairable, even though they may be damaged. Disassembling the window glass in warm water helps to soften the putty, minimize breakage, and reduce exposure to airborne dust. Photo: Neal A. Vogel.

Not Recommended
Replacing an entire window from the restoration period when repair of materials and limited replacement of deteriorated or missing parts are appropriate.

Failing to reuse serviceable window hardware such as brass sash lifts and sash locks.

Using a substitute material for the replacement part that does not convey the visual appearance of the surviving parts of the window or that is physically or chemically incompatible.


Replacing in kind a window feature from the restoration period that is too deteriorated to repair using the same sash and pane configuration and other design details. If using the same kind of material is not technically or economically feasible when replacing windows deteriorated beyond repair, then a compatible substitute material may be considered. The new work should be unobtrusively dated to guide future research and treatment.

photo of duplicated sash and pane detail in Restoration

Using the same sash and pane details in restoration is key to achieving a successful window project. Photo: NPS files.

Not Recommended
Removing a window feature from the restoration period that is unrepairable and not replacing it; or failing to document the new work.

The following Restoration work is highlighted to indicate that it involves the removal or alteration of existing historic windows and windows features that would be retained in Preservation and Rehabilitation treatments; and the replacement of missing window features from the restoration period using all new materials.

Removing Existing Features from Other Historic Periods

Removing or altering windows or window features from other historic periods, such as later single-pane glazing or inappropriate shutters.

Documenting materials and features dating from other periods prior to their alteration or removal. If possible, selected examples of these features or materials should be stored to facilitate future research.

Not Recommended
Failing to remove a window feature from another period, thus confusing the depiction of the building's significance.

Failing to document window features from other historic periods that are removed from the building so that a valuable portion of the historic record is lost.

Re-creating Missing Features from the Restoration Period

Re-creating a missing window or window feature that existed during the restoration period based on physical or documentary evidence; for example, duplicating a hoodmold or shutter.

Not Recommended
Constructing a window feature that was part of the original design for the building, but was never actually built; or constructing a feature which was thought to have existed during the restoration period, but for which there is insufficient documentation.



The Approach

Exterior Materials
Architectural Metals

Exterior Features
Entrances + Porches

Interior Features
Structural System Spaces/Features/Finishes
Mechanical Systems



Special Requirements
Energy Efficiency
Health + Safety

The Standards



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Historical Overview