Guidelines For Rehabilitating Historic Buildings: New Additions To Historic Buildings

Procedure code:
National Park Service, Preservation Assistance Division
General Requirements
Reference Standards
Last Modified:


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

NOTE:  Although the work in these sections is quite often an
important aspect of rehabilitation projects, it is usually NOT part
of the overall process of preserving character-defining features
(maintenance, repair, replacement); rather, such work is assessed
for its potential negative impact on the building's historic
character.  For this reason, particular care must be taken not to
obscure, radically change, damage, or destroy character-defining
features in the process of rehabilitation work to meet new use

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
Architectural Metals.  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.


An attached exterior addition to an historic building expands its
"outer limits" to create a new profile.  Because such expansion has
the capability to radically change the historic appearance, an
exterior addition should be considered only after it has been
determined that the new use cannot be successfully met by altering
non-character-defining interior spaces.  If the new use cannot be
met in this way, then an attached exterior addition is usually an
acceptable alternative.  New additions should be designed and
constructed so that the character-defining features of the historic
building are not radically changed, obscured, damaged, or destroyed
in the process of rehabilitation.  New design should always be
clearly differentiated so that the addition does not appear to be
part of the historic resources.

1.   Recommended:

    -    Placing functions and services required for the new use
         in non-character-defining interior spaces rather than
         installing a new addition.

    Not Recommended:

    -    Expanding the size of the historic building by
         constructing a new addition when the new use could be met
         by altering non-character-defining interior spaces.

2.   Recommended:

    -    Constructing a new addition so that there is the least
         possible loss of historic materials and so that
         character-defining features are not obscured, damaged, or

    Not Recommended:

    -    Attaching a new addition so that the character-defining
         features of the historic building are obscured, damaged,
         or destroyed.

3.   Recommended:

    -    Locating the attached exterior addition at the rear or on
         an inconspicuous side of a historic building; and
         limiting its size and scale in relationship to the
         historic building.

    Not Recommended:

    -    Designing a new addition so that its size and scale in
         relation to the historic building are out of proportion,
         thus diminishing the historic character.

4.   Recommended:

    -    Designing new additions in a manner that makes clear what
         is historic and what is new.

    Not Recommended:

    -    Duplicating the exact form, material, style, and
         detailing of the historic building in the new addition so
         that the new work appears to be part of the historic

    -    Imitating an historic style or period of architecture in
         new additions, especially for contemporary uses such as
         drive-in banks or garages.

5.   Recommended:

    -    Considering the attached exterior addition both in terms
         of the new use and the appearance of other buildings in
         the historic district or neighborhood.  Design for the
         new work may be contemporary or may reference design
         motifs from the historic building.  In either case, it
         should always be clearly differentiated from the historic
         building and be compatible in terms of mass, materials,
         relationship of solids to voids, and color.

    Not Recommended:

    -    Designing and constructing new additions that result in
         the diminution or loss of the historic character of the
         resource, including its design, materials, workmanship,
         location, or setting.

    -    Using the same wall plane, roof line, cornice height,
         materials, siding lap or window type to make additions
         appear to be a part of the historic building.

6.   Recommended:

    -    Placing new additions such as balconies and greenhouses
         on non-character-defining elevations and limiting the
         size and scale in relationship to the historic building.

    Not Recommended:

    -    Designing new additions such as multistory greenhouse
         additions that obscure, damage, or destroy character-
         defining features of the historic building.

7.   Recommended:

    -    Designing additional stories, when required for the new
         use, that are set back from the wall plane and are an
         inconspicuous as possible when viewed from the street.

    Not Recommended:

    -    Constructing additional stories so that the historic
         appearance of the building is radically changed.

                         END OF SECTION

Last Reviewed 2015-06-02