Historic Preservation - Technical Procedures

Preservation Briefs: 18 Rehabilitating Interiors In Historic Buildings
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Preservation Briefs 18, National Park Service, Pad
General Requirements
Special Project Procedures
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Preservation Briefs: 18 Rehabilitating Interiors In Historic Buildings
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The link immediately below connects to the latest version of National Park Service Preservation Brief 18:



H. Ward Jandl

This standard includes the bulk of information contained in the
original Preservation Brief developed by the National Park Service.
To obtain a complete copy of this brief, including figures and
illustrations, please contact:  

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While the exterior of a building may be its most prominent visible
aspect, or its "public face," its interior can be even more
important in conveying the building's history and development over
time. Rehabilitation within the context of the Secretary of the
Interior's Standards for Rehabilitation calls for the preservation
of exterior and interior portions or features of the building that
are significant to its historic, architectural and cultural values.

Interior components worthy of preservation may include the
building's plan (sequence of spaces and circulation patterns), the
building's spaces (rooms and volumes), individual architectural
features, and the various finishes and materials that make up the
walls, floors, and ceilings. A theater auditorium or sequences of
rooms such as double parlors or a lobby leading to a stairway that
ascends to a mezzanine may comprise a building's most important
spaces. Individual rooms may contain notable features such as
plaster cornices, millwork, parquet wood floors, and hardware.
Paints, wall coverings, and finishing techniques such as graining,
may provide color, texture, and patterns which add to a building's
unique character.

Virtually all rehabilitations of historic buildings involve some
degree of interior alteration, even if the buildings are to be used
for their original purpose. Interior rehabilitation proposals may
range from preservation of existing features and spaces to total
reconfigurations. In some cases, depending on the building,
restoration may be warranted to preserve historic character
adequately; in other cases, extensive alterations may be perfectly

This Preservation Brief has been developed to assist building
owners and architects in identifying and evaluating those elements
of a building's interior that contribute to its historic character
and in planning for the preservation of those elements in the
process of rehabilitation. The guidance applies to all building
types and styles, from 18th century churches to 20th century office
buildings. The Brief does not attempt to provide specific advice on
preservation techniques and treatments, given the vast range of
buildings, but rather suggests general preservation approaches to
guide construction work.


Before determining what uses might be appropriate and before
drawing up plans, a thorough professional assessment should be
undertaken to identify those tangible architectural components
that, prior to rehabilitation, convey the building's sense of time
and place--that is, its "historic character".  Such an assessment,
accomplished by walking through and taking account of each element
that makes up the interior, can help ensure that a truly compatible
use for the building, one that requires minimal alteration to the
building, is selected.


A review of the building's history will reveal why and when the
building achieved significance or how it contributes to the
significance of the district. This information helps to evaluate
whether a particular rehabilitation treatment will be appropriate
to the building and whether it will preserve those tangible
components of the building that convey its significance for
association with specific events or persons along with its
architectural importance. In this regard, National Register files
may prove useful in explaining why and for what period of time the
building is significant. In some cases research may show that later
alterations are significant to the building.  In other cases, the
alterations may be without historical or architectural merit, and
may be removed in the rehabilitation.


Interiors of buildings can be seen as a series of primary and
secondary spaces. The goal of the assessment is to identify which
elements contribute to the building's character and which do not.
Sometimes it will be the sequence and flow of spaces, and not just
the individual rooms themselves, that contribute to the building's
character. This is particularly evident in buildings that have
strong central axes or those that are consciously asymmetrical in
design. In other cases, it may be the size or shape of the space
that is distinctive. The importance of some interiors may not be
readily apparent based on a visual inspection.  Sometimes rooms
that do not appear to be architecturally distinguished are
associated with important persons and events that occurred within
the building.

Primary spaces are found in all buildings, both monumental and
modest. Examples may include foyers, corridors, elevator lobbies,
assembly rooms, stair halls, and parlors. Often they are the places
in the building that the public uses and sees. Sometimes they are
the most architecturally-detailed spaces in the building, carefully
proportioned and finished with costly materials. They may be
functionally and architecturally related to the building's external
appearance. In a simpler building, a primary space may be
distinguishable only by its location, size, proportions, or use.
Primary spaces are always important to the character of the
building and should be preserved.

Secondary spaces are generally more utilitarian in appearance and
size than primary spaces. They may include areas and rooms that
service the building, such as bathrooms, and kitchens. Examples of
secondary spaces in a commercial or office structure may include
storerooms, service corridors, and in some cases, the offices
themselves. Secondary spaces tend to be of less importance to the
building and may accept greater change in the course of work
without compromising the building's historic character.

Spaces are often designed to interrelate both visually and
functionally. The sequence of spaces, such as vestibule-hall-parlor
or foyer-lobby-stair-auditorium or stairhall-corridor-classroom,
can define and express the building's historic function and unique
character. Important sequences of spaces should be identified and
retained in the rehabilitation project.

Floor plans may also be distinctive and characteristic of a style
of architecture or a region. Examples include Greek Revival and
shotgun houses. Floor plans may also reflect social, educational,
and medical theories of the period. Many 19th century psychiatric
institutions, for example, had plans based on the ideas of Thomas
Kirkbride, a Philadelphia doctor who authored a book on asylum

In addition to evaluating the relative importance of the various
spaces, the assessment should identify architectural features and
finishes that are part of the interior's history and character.
Marble or wood wainscoting in corridors, elevator cabs, crown
molding, baseboards, mantels, ceiling medallions, window and door
trim, tile and parquet floors, and staircases are among those
features that can be found in historic buildings. Architectural
finishes of note may include grained woodwork, marbleized columns,
and plastered walls. Those features that are characteristic of the
building's style and period of construction should, again, be
retained in the rehabilitation.

Features and finishes, even if machine made and not exhibiting
particularly fine craftsmanship, may be character defining; these
would include pressed metal ceilings and millwork around windows
and doors. The interior of a plain, simple-detailed worker's house
of the 19th century may be as important historically as a richly
ornamented, high-style townhouse of the same period. Both
resources, if equally intact, convey important information about
the early inhabitants and deserve the same careful attention to
detail in the preservation process.

The location and condition of the building's existing heating,
plumbing, and electrical systems also need to be noted in the
assessment. The visible features of historic systems--radiators,
grilles, light fixtures, switchplates, bathtubs, etc.--can
contribute to the overall character of the building, even if the
systems themselves need upgrading.


In assessing a building's interior, it is important to ascertain
the extent of alteration and deterioration that may have taken
place over the years; these factors help determine what degree of
change is appropriate in the project. Close examination of existing
fabric and original floor plans, where available, can reveal which
alterations have been additive, such as new partitions inserted for
functional or structural reasons and historic features covered up
rather than destroyed. It can also reveal which have been
subtractive, such as key walls removed and architectural features
destroyed. If an interior has been modified by additive changes and
if these changes have not acquired significance, it may be
relatively easy to remove the alterations and return the interior
to its historic appearance. If an interior has been greatly altered
through subtractive changes, there may be more latitude in making
further alterations in the process of rehabilitation because the
integrity of the interior has been compromised. At the same time,
if the interior had been exceptionally significant, and solid
documentation on its historic condition is available,
reconstruction of the missing features may be the preferred option.

It is always a recommended practice to photograph interior spaces
and features thoroughly prior to rehabilitation. Measured floor
plans showing the existing conditions are extremely useful. This
documentation is invaluable in drawing up rehabilitation plans and
specifications and in assessing the impact of changes to the
property for historic preservation certification purposes.


If the historic building is to be rehabilitated, it is critical
that the new use not require substantial alteration of distinctive
spaces or removal of character defining architectural features or
finishes. If an interior loses the physical vestiges of its past as
well as its historic function, the sense of time and place
associated both with the building and the district in which it is
located is lost.

The recommended approaches that follow address common problems
associated with the rehabilitation of historic interiors and have
been adapted from the Secretary of the Interior's Standards for
Rehabilitation and Guidelines for Rehabilitating Historic
Buildings. Adherence to these suggestions can help ensure that
character-defining interior elements are preserved in the process
of rehabilitation. The checklist covers a range of situations and
is not intended to be all inclusive. Readers are strongly
encouraged to review the full set of guidelines before undertaking
any rehabilitation project.


Buildings undergoing rehabilitation must comply with existing
building, life safety and fire codes. The application of codes to
specific projects varies from building to building, and town to
town. Code requirements may make some reuse proposals impractical;
in other cases, only minor changes may be needed to bring the
project into compliance. In some situations, it may be possible to
obtain a code variance to preserve distinctive interior features.
(It should be noted that the Secretary's Standards for
Rehabilitation take precedence over other regulations and codes in
determining whether a rehabilitation project qualifies for Federal
tax benefits.) A thorough understanding of the applicable
regulations and close coordination with code officials, building
inspectors, and fire marshals can prevent the alteration of
significant historic interiors.


Rehabilitation and restoration work should be undertaken by
professionals who have an established reputation in the field.

Given the wide range of interior work items, from ornamental
plaster repair to marble cleaning and the application of graining,
it is possible that a number of specialists and subcontractors will
need to be brought in to bring the project to completion. State
Historic Preservation Officers and local preservation organizations
may be a useful source of information in this regard. Good sources
of information on appropriate preservation techniques for specific
interior features and finishes include the Bulletin of the
Association for Preservation Technology and The Old-House Journal;
other useful publications are listed in the bibliography.


Architectural features and finishes to be preserved in the process
of rehabilitation should be clearly marked on plans and at the
site. This step, along with careful supervision of the interior
demolition work and protection against arson and vandalism, can
prevent the unintended destruction of architectural elements that
contribute to the building's historic character.

Protective coverings should be installed around architectural
features and finishes to avoid damage in the course of construction
work and to protect workers. Staircases and floors, in particular,
are subjected to dirt and heavy wear, and the risk exists of
incurring costly or irreparable damage. In most cases, the best and
least costly preservation approach is to design and construct a
protective system that enables stairs and floors to be used, yet
protects them from damage. Other architectural features such as
mantels, doors, wainscotting, and decorative finishes may be
protected by using heavy canvas or plastic sheets.


In many cases, the interior of an historic building is as important
as its exterior. The careful identification and evaluation of
interior architectural elements, after undertaking research on the
building's history and use, is critically important before changes
to the building are contemplated. Only after this evaluation should
new uses be decided and plans be drawn up. The best rehabilitation
is one that preserves and protects those rooms, sequences of
spaces, features and finishes that define and shape the overall
historic character of the building.


1.   Retain and preserve floor plans and interior spaces that are
    important in defining the overall historic character of the
    building. This includes the size, configuration, proportion,
    and relationship of rooms and corridors; the relationship of
    features to spaces; and the spaces themselves such as lobbies,
    reception halls, entrance halls, double parlors, theaters,
    auditoriums, and important industrial or commercial use
    spaces. Put service functions required by the building's new
    use, such as bathrooms, mechanical equipment, and office
    machines, in secondary spaces.

2.   Avoid subdividing spaces that are characteristic of a building
    type or style or that are directly associated with specific
    persons or patterns of events. Space may be subdivided both
    vertically through the insertion of new partitions or
    horizontally through insertion of new floors or mezzanines.
    The insertion of new additional floors should be considered
    only when they will not damage or destroy the structural
    system or obscure, damage, or destroy character-defining
    spaces, features, or finishes. If rooms have already been
    subdivided through an earlier insensitive renovation, consider
    removing the partitions and restoring the room to its original
    proportions and size.

3.   Avoid making new cuts in floors and ceilings where such cuts
    would change character-defining spaces and the historic
    configuration of such spaces. Inserting a new atrium or a
    light well is appropriate only in very limited situations
    where the existing interiors are not historically or
    architecturally distinguished.

4.   Avoid installing dropped ceilings below ornamental ceilings or
    in rooms where high ceilings are part of the building's
    character. In addition to obscuring or destroying significant
    details, such treatments will also change the space's
    proportions. If dropped ceilings are installed in buildings
    that lack character-defining spaces, such as mills and
    factories, they should be well set back from the windows so
    they are not visible from the exterior.

5.   Retain and preserve interior features and finishes that are
    important in defining the overall historic character of the
    building. This might include columns, doors, cornices,
    baseboards, fireplaces and mantels, paneling, light fixtures,
    elevator cabs, hardware, flooring and wallpaper, plaster,
    paint, and finishes such as stenciling, marbleizing, and
    graining; and other decorative materials that accent interior
    features and provide color, texture, and patterning to walls,
    floors, and ceilings.

6.   Retain stairs in their historic configuration and location. If
    a second means of egress is required, consider constructing
    new stairs in secondary spaces. (For guidance on designing
    compatible new additions, see Preservation Brief 14, "New
    Exterior Additions to Historic Buildings.") The application of
    fire-retardant coatings, such as intumescent paints; the
    installation of fire suppression systems, such as sprinklers;
    and the construction of glass enclosures can in many cases
    permit retention of stairs and other character-defining

7.   Retain and preserve visible features of early mechanical
    systems that are important in defining the overall historic
    character of the building, such as radiators, vents, fans,
    grilles, plumbing fixtures, switchplates, and lights. If new
    heating, air conditioning, lighting and plumbing systems are
    installed, they should be done in a way that does not destroy
    character-defining spaces, features and finishes. Ducts,
    pipes, and wiring should be installed as inconspicuously as
    possible: in secondary spaces, in the attic or basement if
    possible, or in closets.

8.   Avoid "furring out" perimeter walls for insulation purposes.
    This requires unnecessary removal of window trim and can
    change a room's proportions. Consider alternative means of
    improving thermal performance, such as installing insulation
    in attics and basements and adding storm windows.

9.   Avoid removing paint and plaster from traditionally finished
    surfaces, to expose masonry and wood. Conversely, avoid
    painting previously unpainted millwork. Repairing deteriorated
    plaster work is encouraged. If the plaster is too deteriorated
    to save, and the walls and ceilings are not highly ornamented,
    gypsum board may be an acceptable replacement material. The
    use of paint colors appropriate to the period of the
    building's construction is encouraged.

10.  Avoid using destructive methods--propane and butane torches or
    sandblasting--to remove paint or other coatings from historic
    features. Avoid harsh cleaning agents that can change the
    appearance of wood. (For more information regarding
    appropriate cleaning methods, see 04510-05-S "Preservation
    Briefs 6:  Dangers of Abrasive Cleaning to Historic

                         END OF SECTION

Last Reviewed 2012-09-10