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Historic Preservation - Technical Procedures

Spectitle:
Guidelines For Rehabilitating Historic Buildings: Windows

Procedure code:
0109110S

Source:
National Park Service, Preservation Assistance Division

Division:
General Requirements

Section:
Reference Standards

Last Modified:
02/24/2012

Details:
Guidelines For Rehabilitating Historic Buildings: Windows



GUIDELINES FOR REHABILITATING HISTORIC BUILDINGS:  WINDOWS


U.S. Department of the Interior
National Park Service
Preservation Assistance Division
Washington, D.C.


An illustrated booklet addressing the Secretary's Standards and the
guidelines is available from the U.S. Government Printing Office.
The title is "The Secretary of the Interior's Standards for
Rehabilitation & Illustrated Guidelines for Rehabilitating Historic
Buildings", ISBN 0-16-035979-1.

Each of the guidelines included in the booklet mentioned above have
been separated into individual entries for specific use in HBPP.
This entry represents one of many guidelines included in the
booklet and describes RECOMMENDED and NOT RECOMMENDED applications
of the Secretary of the Interior's Standards as they relate to
Windows.  For a list of the Secretary of the Interior's Standards
for Rehabilitation, see 01091-04-S; For general information
relating to the purpose, organization and content of the individual
guidelines, see 01091-05-S.  Both of these entries should be
referenced along with the information contained in this document.


BUILDING EXTERIOR

WINDOWS:

A highly decorative window with an unusual shape, or glazing
pattern, or color is most likely identified immediately as a
character-defining feature of the building.  It is far more
difficult, however, to assess the importance of repeated windows on
a facade, particularly if they are individually simple in design
and material, such as the large, multi-paned sash of many
industrial buildings.  Because rehabilitation projects frequently
include proposals to replace window sash or even entire windows to
improve thermal efficiency or to create a new appearance, it is
essential that their contribution to the overall historic character
of the building be assessed together with their physical condition
before specific repair or replacement work is undertaken.


IDENTIFYING, RETAINING AND PRESERVING

1.   Recommended:

    -    Identifying, retaining, and preserving windows -- and
         their functional and decorative features -- that are
         important in defining the overall historic character of
         the building.  Such features can include frames, sash,
         muntins, glazing, sills, heads, hoodmolds, panelled or
         decorated jambs and moldings, and interior and exterior
         shutters and blinds.

    Not Recommended:

    -    Removing or radically changing windows which are
         important in defining the overall historic character of
         the building so that, as a result, the character is
         diminished.

    -    Changing the number, location, size or glazing pattern of
         windows, through cutting new openings, blocking-in
         windows, and installing replacement sash which does not
         fit the historic window opening.

    -    Changing the historic appearance of windows through the
         use of inappropriate designs, materials, finishes, or
         colors which radically change the sash, depth of reveal,
         and muntin configuration; the reflectivity and color of
         the glazing; or the appearance of the frame.

    -    Obscuring historic window trim with metal or other
         material.

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


PROTECTING AND MAINTAINING

1.   Recommended:

    -    Protecting and maintaining the wood and architectural
         metal 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.

    Not Recommended:

    -    Failing to provide adequate protection of materials on a
         cyclical basis so that deterioration of the windows
         results.

2.   Recommended:

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

    Not Recommended:

    -    Retrofitting or replacing windows rather than maintaining
         the sash, frame, and glazing.

3.   Recommended:

    -    Evaluating the overall 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 undertake adequate measures to assure the
         preservation of historic windows.


REPAIRING

1.   Recommended:

    -    Repairing window frames and sash by patching, splicing,
         consolidating or otherwise reinforcing.  Such repair may
         also include replacement in kind of those parts that are
         either extensively deteriorated or are missing when there
         are surviving prototypes such as architraves, hoodmolds,
         sash, sills, and interior or exterior shutters and
         blinds.

    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 such as
         brass 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

1.   Recommended:

    -    Replacing in kind an entire window that is too
         deteriorated to repair -- if the overall form and
         detailing are still evident -- using the physical
         evidence to guide the new work.  If using the same kind
         of material is not technically or economically feasible,
         then a compatible substitute material may be considered.

    Not Recommended:

    -    Removing a character-defining window that is unrepairable
         and blocking it in; or replacing it with a new window
         that does not convey the same visual appearance.


NOTE:  THE FOLLOWING REPRESENTS PARTICULARLY COMPLEX TECHNICAL OR
DESIGN ASPECTS OF REHABILITATION PROJECTS AND SHOULD ONLY BE
CONSIDERED AFTER THE PRESERVATION CONCERNS LISTED ABOVE HAVE BEEN
ADDRESSED.

DESIGN FOR MISSING HISTORIC FEATURES

1.   Recommended:

    -    Designing and installing new windows when the historic
         windows (frame, sash and glazing) are completely missing.
         The replacement windows may be an accurate restoration
         using historical, pictorial, and physical documentation;
         or be a new design that is compatible wit the window
         openings and the historic character of the building.

    Not Recommended:

    -    Creating a false historical appearance because the
         replaced window is based on insufficient historical,
         pictorial, and physical documentation.

    -    Introducing a new design that is incompatible with the
         historic character of the building.


ALTERATIONS/ADDITIONS FOR THE NEW USE

1.   Recommended:

    -    Designing and installing additional windows on rear or
         other non-character-defining elevations if required by
         the new use.  New windows openings may also be cut into
         exposed party walls.  Such design should be compatible
         with the overall design of the building, but not
         duplicate the fenestration pattern and detailing of a
         character-defining elevation.

    Not Recommended:

    -    Installing new windows, including frames, sash, and
         muntin configuration that are incompatible with the
         building's historic appearance or obscure, damage, or
         destroy character-defining features.

2.   Recommended:

    -    Providing a setback in the design of dropped ceilings
         when they are required for the new use to allow the full
         height of the window openings.

    Not Recommended:

    -    Inserting new floors or furred-down ceilings which cut
         across the glazed areas of windows so that the exterior
         form and appearance of  the windows are changed.

                         END OF SECTION