Historic Preservation - Technical Procedures

Guidelines For Rehabilitating Historic Buildings: General
Procedure code:
National Park Service, Preservation Assistance Division
General Requirements
Reference Standards
Last Modified:
Guidelines For Rehabilitating Historic Buildings: General
Last Modified:


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.

This reference includes general information describing the purpose,
organization and content of the Guidelines for Rehabilitating
Historic Buildings.  Each of the guidelines included in the booklet
mentioned above have been separated into individual entries for
specific use in HBPP.  This reference should be used along with
each individual guideline in applying the Secretary of the
Interior's Standards to historic buildings.  The related guidelines
include HBPP sequence numbers 01091-06-S through 01091-19-S.


The Guidelines were initially developed in 1977 to help property
owners, developers, and Federal managers apply the Secretary of the
Interior's "Standards for Rehabilitation" during the project
planning stage by providing general design and technical
recommendations.  Unlike the Standards, the Guidelines are not
codified as program requirements.  Together with the "Standards for
Rehabilitation" they provide a model process for owners,
developers, and Federal agency managers to follow.

The Guidelines are intended to assist in applying the Standards to
projects generally; consequently, they are not meant to give case-
specific advice or address exceptions or rare instances.  For
example, they cannot tell an owner or developer which features of
their own historic building are important in defining the historic
character and must be preserved - although examples are provided in
each section - or which features could be altered, if necessary,
for the new use.  This kind of careful case-by-case decision making
is best accomplished by seeking assistance from qualified historic
preservation professionals in the planning stage of the project.
Such professionals include architects, architectural historians,
historians, archaeologists, and others who are skilled in the
preservation, rehabilitation, and restoration of historic

The Guidelines pertain to historic buildings of all sizes,
materials, occupancy, and construction types; and apply to interior
and exterior work as well as new exterior additions.  Those
approaches, treatments, and techniques that are consistent with the
Secretary of the Interior's "Standards for Rehabilitation" are
listed under the heading, "Recommended"; those approaches,
treatments, and techniques which could adversely affect a
building's historic character are listed under the heading, "Not

To provide clear and consistent guidance for owners, developers,
and Federal agency managers to follow, the "Recommended courses of
action in each section are listed in order of historic preservation
concerns so that a rehabilitation project may be successfully
planned and completed - one that, first, assures the preservation
of a building's important "character-defining" architectural
materials and features and, second, makes possible an efficient
contemporary use.  Rehabilitation guidance in each section begins
with protection and maintenance, that work which should be
maximized in every project to enhance overall preservation goals.
Next, where some deterioration is present, repair of the building's
historic materials and features is recommended.  Finally, when
deterioration is so extensive that repair is not possible, the most
problematic area of work is considered: replacement of historic
materials and features with new materials.

To further guide the owner and developer in planning a successful
rehabilitation project, those complex design issues dealing with
new use requirements such as alterations and additions are
highlighted at the end of each section to underscore the need for
particular sensitivity in these areas.


The guidance that is basic to the treatment of all historic
detailing of those architectural materials and features that are
important in defining the historic character - is always listed
under the heading, "Recommended".  The parallel heading, "Not
Recommended", lists the types of actions that are most apt to cause
the diminution or even loss of the building's historic character.
It should be remembered, however, that such loss of character is
just as often caused by the cumulative effect of a series of
actions that would seem to be minor interventions.  Thus, the
guidance in ALL of the "Not Recommended" headings must be viewed in
that larger context, e.g., for the total impact on a historic


After identifying those materials and features that are important
and must be retained in the process of rehabilitation work, then
PROTECTING AND MAINTAINING them are addressed.  Protection
generally involves the least degree of intervention and is
preparatory to other work.  For example, protection includes the
maintenance of historic material through treatments such as rust
removal, caulking, limited paint removal, and re-application of
protective coatings; the cyclical cleaning of roof gutter systems;
or installation of fencing, protective plywood, alarm systems and
other temporary protective measures.  Although a historic building
will usually require more extensive work, an overall evaluation of
its physical condition should always begin at this level.


Next, when the physical condition of character-defining materials
and features warrants additional work REPAIRING is recommended.
Guidance for the repair of historic materials such as masonry,
wood, and architectural metals again begins with the least degree
of intervention possible such as patching, piecing-in, splicing,
consolidating, or other wise reinforcing or upgrading them
according to recognized preservation methods.  Repairing also
includes the limited replacement in kind - or with compatible
substitute material - of extensively deteriorated or missing parts
of features when there are surviving prototypes (for example,
brackets, dentils, steps, plaster, or portions of slate or tile
roofing).  Although using the same kind of material is always the
preferred option, substitute material is acceptable if the form and
design as well as the substitute material itself convey the visual
appearance of the remaining parts of the feature and finish.


Following repair in the hierarchy, guidance is provided for
REPLACING an entire character-defining feature with new material
because the level of deterioration or damage of materials precludes
repair (for example, an exterior cornice; an interior staircase, or
a complete porch or storefront).  If the essential form and
detailing are still evident so that the physical evidence can be
used to re-establish the feature as an integral part of the
rehabilitation project, then its replacement is appropriate.  Like
the guidance for repair, the preferred option is always replacement
of the entire feature in kind, that is, with the same material.
Because this approach may not always be technically or economically
feasible, provisions are made to consider the use of a compatible
substitute material.

It should be noted that, while the National Park Service guidelines
recommend the replacement of an entire character-defining feature
under certain well-defined circumstances, they NEVER recommend
removal and replacement with new material of a feature that -
although damaged or deteriorated - could reasonably be repaired and
thus preserved.


When an entire interior or exterior feature is missing (for
example, an entrance, or cast iron facade; or a principal
staircase), it no longer plays a role in physically defining the
historic character of the building unless it can be accurately
recovered in form and detailing through the process of carefully
documenting the historical appearance.  Where an important
architectural feature is missing, its recovery is always
recommended in the guidelines as the FIRST or preferred, course of
action.  Thus, if adequate historical, pictorial, and physical
documentation exists so that the feature may be accurately
reproduced, and if it is desirable to re-establish the feature as
part of the building's historical appearance, then designing and
constructing a new feature based on such information is
appropriate.  However, a SECOND acceptable option for the
replacement feature is a new design that is compatible with the
remaining character-defining features of the historic building.
The new design should always take into account the size, scale, and
material of the historic building itself and, more importantly,
should be clearly differentiated so that a false historical
appearance is not created.


Some exterior and interior alterations to the historic building are
generally needed to assure its continued use, but it is most
important that such alterations do not radically change, obscure,
or destroy character-defining spaces, materials, features, or
finishes.  Alterations may include providing additional parking
space on an existing historic building site; cutting new entrances
or windows on secondary elevations; inserting an additional floor;
installing an entirely new mechanical system; or creating an atrium
or light well.  Alteration may also include the selective removal
of buildings or other features of the environment or building site
that are intrusive and therefore detract from the overall historic

The construction of an exterior addition to a historic building may
seem to be essential for the new use, but it is emphasized in the
guidelines that such new additions should be avoided, if possible,
and considered ONLY after it is determined that those needs cannot
be met by altering secondary, i.e., non character-defining interior
spaces.  If, after a thorough evaluation of interior solutions, an
exterior addition is still judged to be the only viable
alternative, it should be designed and constructed to be clearly
differentiated from the historic building and so that the
character-defining features are not radically changed, obscured,
damaged or destroyed.

Additions to historic buildings are referenced within specific
sections of the guidelines such as Site, Roof, Structural Systems,
etc., but are also considered in more detail in a separate
standard, 01091-19-S "Guidelines for Rehabilitating Historic
Buildings:  New Additions to Historic Buildings".


These standards of rehabilitation guidance address work done to
meet health and safety code requirements (for example, providing
barrier-free access to historic buildings); or retrofitting
measures to conserve energy (for example, installing solar
collectors in an unobtrusive location on the site).  Although this
work is quite often an important aspect of rehabilitation projects
it is usually not part of the overall process of protecting or
repairing character-defining features; 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 radically change, obscure, damage, or destroy character-
defining materials or features in the process of rehabilitation
work to meet code and energy requirements.  For specific guidance,
see 01091-17-S "Guidelines...Health and Safety Code Requirements"
and 01091-18-S "Guidelines...Energy Retrofitting".

Specific information on rehabilitation and preservation technology
may be obtained by writing to the National Park Service, at the
addresses listed below.

-    Preservation Assistance Division
    National Park Service
    P.O. Box 37127
    Washington, DC  20013-7127

-    National Historic Preservation Programs
    Western Regional Office
    National Park Service
    600 Harrison Street, Ste. 600
    San Francisco, CA  94107-1372

-    Division of Cultural Resources
    Rocky Mountain Regional Office
    National Park Service
    12795 West Alameda Pkwy.
    P.O. Box 25287
    Denver, CO  80225

-    Preservation Services Division
    Southeast Regional Office
    National Park Service
    75 Spring St. SW., Room 1140
    Atlanta, GA  30303

-    Office of Cultural Programs
    Mid-Atlantic Regional Office
    National Park Service
    Customs House
    Second and Chestnut Streets, Rm. 251
    Philadelphia, PA  19106

-    Cultural Resources Division
    Alaska Regional Office
    National Park Service
    2525 Gambell St., Rm. 107
    Anchorage, AK  99503

                         END OF SECTION
Last Reviewed 2012-02-24