GSA Alteration Guidelines For Interiors

Technical Procedures Disclaimer

Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.


We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.

This standard was extracted from GSA's Maintenance, Repair and Alteration of Historic Buildings reference document from 1981. The following information includes general GSA guidelines to consider when planning interior alterations to historic buildings.

Standard alteration techniques and solutions often will not preserve the architectural character of significant interiors. In general, alterations to such spaces should conceal necessary work, particularly electrical and mechanical equipment, behind the original finishes and within the original structure of the building.

The following design considerations will be helpful.

  • Preserve all original finishes, trim and ornament of the room, and remove any existing later alterations or non-original elements.
  • Repair or replace any missing original features to exact original design and appearance, budget permitting.
  • Ensure that custodial work and routine maintenance are carried out with care and with only mild, dilute chemical cleaners, if any.
  • Locate tenants in appropriate spaces. Organize heavy traffic to avoid damaging sensitive areas.
  • Do not crowd rooms with furnishings that cover architectural detail.
  • Carefully design and place any necessary electrical outlets or HVAC grilles to be unobtrusive and paint them to match adjacent finishes.
  • Remove fluorescent lighting and use concealed uplighting for general illumination and individual task lights at work surfaces. Restore original fixtures, if possible, for general illumination.
  • Alterations should be compatible with the original space and materials. Use materials and installations that are visually related to finishes and materials in the remainder of the building.
  • Permit only changes or alterations to materials or finishes necessary for restoration.
  • Investigate opportunities to conceal all electrical and mechanical equipment when budget permits. Exposed installations of mechanical systems must be laid out as unobtrusively as possible, and should not cover or obscure original elements.
  • Do not make alterations that attach permanently to original elements of the room. When it is necessary to cover or obscure original elements with alterations, alterations should be easily removable without damage to permanent finishes.
  • Retain original blinds whenever possible. [The large slat venetian blinds closely matching the period ones, are again being marketed and are regaining favor as a contemporary window treatment.] If an accurate restoration of sun control devices is infeasible, use an unobtrusive contemporary treatment (e.g., thin-line, horizontal blinds). DO NOT: paint over window glass; change clear glass to frosted or translucent glass; replace glass with solid filler panel; use vertical blinds of wall-to-wall drapery; cover decorative window surrounds with shades or blinds; use roller shades.
  • Test ceiling for original colors and details and restore to exact original condition.
  • Preserve, maintain and repair and match flooring wherepossible. If intensive use is damaging the flooring, install high quality carpeting or new protective coatings, but do not use adhesives or tacks in a way that will damage original floor.

NOTE: Contact your regional historic preservation officer (RHPO) for further guidance.