Secretary of the Interior Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings

The Standards were developed by the Secretary of the Interior to guide work undertaken on historic buildings. They are used by the National Park Service to determine if a historic building rehabilitation qualifies for federal tax credits. They are also used to guide the preservation of historic federal & private properties not seeking tax credits.

The correlating Guidelines were developed in 1977 to help property owners, developers, & Federal managers apply the Secretary of the Interior's "Standards for Rehabilitation." They include guidelines for windows, entrances, and storefronts using an approach of listing Recommended vs. Not Recommended practices.

For purposes of such compliance, rehabilitation is defined as "the act or process of making possible a compatible use for a property through repair, alterations, and additions while preserving those portions or features which convey its historical, cultural, or architectural values." Recognizing that portions of the building or some of its significant features, including windows, may be deteriorated, the stated preferred choice is to repair and preserve those existing features rather than replace them outright. The architect and owner together need to assess the building and its features to determine if repair is indeed possible and the feasibility of going about it. Nonetheless, the standards do go on to allow for replacement where the severity of deterioration prevents such repair or restoration. The requirement in this case is that the new feature shall match the old in design, color, texture, and other visual qualities and, where possible, materials.

Portions applicable to windows are summarized below:

Rehabilitation Strategy: Identify, Retain and Preserve

Recommended

• Identifying, retaining, and preserving windows--and their functional & decorative features - that are important in defining the overall historic character of the building
  • Frames, sash, muntins, glazing, sills, heads, hoodmolds, moldings
• In depth survey of existing conditions

Not Recommended

• Removing or radically changing windows
• Changing the number, location, size or glazing pattern of windows
• Changing the historic appearance of windows
• Obscuring historic window trim
• Stripping windows of historic material
• Replacing windows solely because of peeling paint, broken glass, stuck sash, and high air infiltration.

Rehabilitation Strategy: Protect and Maintain

Recommended

• Protecting and maintaining the materials which comprise the window frame, sash, muntins, and surrounds through appropriate surface treatments
  • Cleaning, rust removal, limited paint removal, and re-application of protective coating systems
• Making windows weathertight by re-caulking and replacing weatherstripping
• Evaluating the overall condition of materials

Not Recommended

• Failing to provide adequate protection of materials on a cyclical basis
• Retrofitting or replacing windows rather than maintaining them
• Failing to undertake adequate measures to assure the protection of historic windows

Rehabilitation Strategy: Repair

Recommended

• Repairing window frames & sash by patching, splicing, consolidating or otherwise reinforcing
  • May include replacement in kind of those parts that are either deteriorated or missing

Not Recommended

• Replacing an entire window when repair of materials and limited replacement of deteriorated or missing parts are appropriate.
• Failing to reuse serviceable window hardware
• Using substitute material for the replacement part that does not convey the visual appearance of the surviving parts of the window