 |
New Exterior Additions to Historic
Buildings: Preservation Concerns
Kay D. Weeks
Because a new exterior
addition to a historic building can damage or destroy
significant materials and can change the building's
character, an addition should be considered only after it has
been determined that the new use cannot be met by altering
nonsignificant, or secondary, interior spaces. If the new use
cannot be met in this way, then an attached addition may be
an acceptable alternative if carefully planned. A new
addition should be constructed in a manner that preserves
significant materials and features and preserves the historic
character. Finally. an addition should be differentiated from
the historic building so that the new work is not confused
with what is genuinely part of the past.
Change is as inevitable
in buildings and neighborhoods as it is in individuals and
families. Never static, buildings and neighborhoods grow,
diminish, and continue to evolve as each era's technological
advances bring conveniences such as heating, street paving,
electricity, and air conditioning; as the effects of violent
weather, uncontrolled fire, or slow unchecked deterioration
destroy vulnerable material, as businesses expand, change
hands, become obsolete, as building codes are established to
enhance life safety and health; or as additional family
living space is alternately needed and abandoned.
Preservationists
generally agree that the history of a building, together with
its site and setting, includes not only the period of
original construction but frequently later alterations and
additions. While each change to a building or neighborhood is
undeniably part of its history--much like events in human
life--not every change is equally important. For example,
when a later, clearly nonsignificant addition is removed to
reveal the original form, materials, and craftsmanship, there
is little complaint about a loss to history.
When the subject of new
exterior additions is introduced, however, areas of agreement
usually tend to diminish. This is understandable because the
subject raises some serious questions. Can a historic
building be enlarged for a new use without destroying what is
historically significant? And just what is significant about
each particular historic building that should be preserved?
Finally, what new construction is appropriate to the old
building?
The vast amount of
literature on the subject of change to America's built
environment reflects widespread interest as well as
divergence of opinion. New additions have been discussed by
historians within a social and political, framework; by
architectural historians in terms of construction technology
and style; and by urban planners as successful or
unsuccessful contextual design. Within the historic
preservation programs of the National Park Service, however,
the focus has been and will continue to be the protection of
those resources identified as worthy of listing in the
National Register of Historic Places.
National Register
Listing--Acknowledging
Change While Protecting
Historical Significance
Entire districts or
neighborhoods may be listed in the National Register of
Historic Places for their significance to a certain period of
American history (e.g., activities in a commercial district
between 1870 and 1910). This "framing" of historic districts
has led to a concern that listing in the National Register
may discourage any physical change beyond a certain
historical period--particularly in the form of attached
exterior additions. This is not the case. National Register
listing does not mean that an entire building or district is
frozen in time and that no change can be made without
compromising the historical significance. It also does not
mean that each portion of a historic building is equally
significant and must be retained intact and without change.
Admittedly, whether an attached new addition is small or
large, there will always be some loss of material and some
change in the form of the historic building. There will also
generally be some change in the relationship between the
buildings and its site, neighborhood or district. Some change
is thus anticipated within each rehabilitation of a building
for a contemporary use.
Scope of National Park
Service Interest in New Exterior Additions
The National Park Service
interest in new additions is simply this--a new addition to a
historic building has the potential to damage and destroy
significant historic material and features and to change its
historic character. A new addition also has the potential to
change how one perceives what is genuinely historic and thus
to diminish those qualities that make the building eligible
for listing in the National Register of Historic Places. Once
these basic preservation issues have been addressed, all
other aspects of designing and constructing a new addition to
extend the useful life of the historic building rest with the
creative skills of the architect.
The intent of this Brief,
then, is to provide guidance to owners and developers
planning additions to their historic buildings. A project
involving a new addition to a historic building is considered
acceptable within the framework of the National Park
Service's standards if it:
1. Preserves significant
historic materials and features; and
2. Preserves the historic
character; and
3. Protects the
historical significance by making a visual distinction
between old and new.
Paralleling these key
points, the Brief is organized into three sections. Case
study examples are provided to point out acceptable and
unacceptable preservation approaches where new use
requirements were met through construction of an exterior
addition. These examples are included to suggest ways that
change to historic buildings can be sensitively accomplished,
not to provide in-depth project analyses, endorse or critique
particular architectural design, or offer cost and
construction data.
1. Preserving
Significant Historic Materials and Features
Connecting a new exterior
addition always involves some degree of material loss to an
external wall of a historic building and, although this is to
be expected, it can be minimized. On the other hand, damage
or destruction of significant materials and craftsmanship
such as pressed brick, decorative marble, cast stone,
terra-cotta, or architectural metal should be avoided, when
possible.
Generally speaking,
preservation of historic buildings is enhanced by avoiding
all but minor changes to primary or "public" elevations.
Historically, features that distinguish one building or a row
of buildings and can be seen from the streets or sidewalks
are most likely to be the significant ones. This can include
window patterns, window hoods, or shutters; porticoes,
entrances, and doorways; roof shapes, cornices, and
decorative moldings; or commercial storefronts with their
special detailing, signs, and glazing. Beyond a single
building, entire blocks of urban or residential structures
are often closely related architecturally by their materials,
detailing, form, and
alignment. Because significant materials and features should
be preserved, not damaged or hidden, the first place to
consider constructing a new addition is where such material
loss will be minimized. This will frequently be on a
secondary side or rear elevation. For both economic and
social reasons, secondary elevations were often constructed
of "common" material and were less architecturally ornate or
detailed.
In constructing the new
addition, one way to minimize overall material loss is simply
to reduce the size of the new addition in relationship to the
historic building. If a new addition will abut the historic
building along one elevation or wrap around a side and rear
elevation, the integration of historic and new interiors may
result in a high degree of loss--exterior walls as well as
significant interior spaces and features. Another way to
minimize loss is to limit the size and number of openings
between old and new. A particularly successful method to
reduce damage is to link the new addition to the historic
block by means of a hyphen or connector. In this way, only
the connecting passageway penetrates a historic side wall;
the new addition can be visually and functionally related
while historic materials remain essentially intact and
historic exteriors remain uncovered.
Although a general
recommendation is to construct a new addition on a secondary
elevation, there are several exceptions. First, there may
simply be no secondary elevation--some important freestanding
buildings have significant materials and features on all
sides, making any aboveground addition too destructive to be
considered. Second, a structure or group of structures
together with their setting (for example, in a National
Historic Park) may be of such significance in American
history that any new addition would not only damage materials
and alter the buildings' relationship to each other and the
setting, but seriously diminish the public's ability to
appreciate a historic event or place. Finally, there are
other cases where an existing side or rear elevation was
historically intended to be highly visible, is of special
cultural importance to the neighborhood, or possesses
associative historical value. Then, too, a secondary
elevation should be treated as if it were a primary elevation
and a new addition should be avoided.
2. Preserving the Historic
Character
The second, equally
important, consideration is whether or not the new addition
will preserve the resource's historic character. The historic
character of each building may differ, but a methodology of
establishing it remains the same. Knowing the uses and
functions a building has served over time will assist in
making what is essentially a physical evaluation. But while
written and pictorial documentation can provide a framework
for establishing the building's history, the historic
character, to a large extent, is embodied in the physical
aspects of the historic building itself--its shape, its
materials, its features, its craftsmanship, its window
arrangements, its colors, its setting, and its interiors. It
is only after the historic character has been correctly
identified that reasonable decisions about the extent--or
limitations--of change can be made.
To meet National Park
Service preservation standards, a new addition must be
"compatible with the size, scale, color, material, and
character" of the building to which it is attached or its
particular neighborhood or district. A new addition will
always change the size or actual bulk of the historic
building. But an addition that bears no relationship to the
proportions and massing of the historic building--in other
words, one that overpowers the historic form and changes the
scale will usually compromise the historic character as well.
The appropriate size for a new addition varies from building
to building; it could never be stated in a tidy square or
cubic footage ratio, but the historic building's existing
proportions, site, and setting can help set some general
parameters for enlargement. To some extent, there is a
predictable relationship between the size of the historic
resource and the degree of change a new addition will
impose.
For example, in the case
of relatively low buildings (small-scale residential or
commercial structures) it is difficult, if not impossible, to
minimize the impact of adding an entire new floor even if the
new addition is set back from the plane of the facade.
Alteration of the historic proportions and profile will
likely change the building's character. On the other hand, a
rooftop addition to an eight story building in a historic
district of other tall buildings might not affect the
historic character simply because the new work would not be
visible from major streets. A number of methods have been
used to help predict the effect of a proposed rooftop
addition on the historic building and district, including
pedestrian sight lines, three-dimensional schematics and
computer-assisted design (CAD). Sometimes a rough full-size
mock up of a section or bay of the proposed addition can be
constructed using temporary material; the mockup can then be
photographed and evaluated from critical vantage
points.
In the case of
freestanding residential structures, the preservation
considerations are generally twofold. First, a large addition
built out on a highly visible elevation can radically alter
the historic form or obscure features such as a decorative
cornice or window ornamentation. Second, an addition that
fills in a planned void on a highly visible elevation (such
as a "U" shaped plan or feature such as a porch) may also
alter the historic form and, as a result, change the historic
character.
Some historic structures
such as government buildings, metropolitan museums, or
libraries may be so massive in size that a large-scale
addition may not compromise the historic character. Yet
similar expansion of smaller buildings would be dramatically
out of scale. In summary, where any new addition is proposed,
correctly assessing the relationship between actual size and
relative scale will be a key to preserving the character of
the historic building.
Constructing the new
addition on a secondary side or rear elevation--in addition
to material preservation--will also address preservation of
the historic character. Primarily, such placement will help
to preserve the building's historic form and relationship to
its site and setting. Historic landscape features, including
distinctive grade variations, need to be respected; and any
new landscape features such as plants and trees kept at a
scale and density that would not interfere with appreciation
of the historic resource itself.
In highly developed urban
areas, locating a new addition on a less visible side or rear
elevation may be impossible simply because there is no
available space. In this instance, there may be alternative
ways to help preserve the historic character. If a new
addition is being connected to the adjacent historic building
on a primary elevation, the addition may be set back from the
front wall plane so the outer edges defining the historic
form are still apparent. In still other cases, some variation
in material, detailing, and color may provide the degree of
differentiation necessary to avoid changing the essential
proportions and character of the historic building.
3. Protecting the
Historical Significance--
Making a Visual
Distinction Between Old and New
The following statement
of approach could be applied equally to the preservation of
districts, sites, buildings, structures, and objects of
National Register significance: "A conservator works within a
conservation ethic so that the integrity of the object as an
historic entity is maintained. The concern is not just with
the original state of the object, but the way in which it has
been changed and used over the centuries. Where a new
intervention must be made to save the object, either to
stabilize it or to consolidate it, it is generally accepted
that those interventions must be clear, obvious, and
reversible. It is this same attitude to change that is
relevant to conservation policies and attitudes to historic
towns. . . " (1)
Rather than establishing
a clear and obvious difference between old and new, it might
seem more in keeping with the historic character simply to
repeat the historic form, material, features, and detailing
in a new addition. But when the new work is indistinguishable
from the old in appearance, then the "real" National Register
property may no longer be perceived and appreciated by the
public. Thus, the third consideration in planning a new
addition is to be sure that it will protect those visual
qualities that made the building eligible for listing in the
National Register of Historic Places.
A question often asked is
what if the historic character is not compromised by an
addition that appears to have been built in the same period?
A small porch or a wing that copied the historic materials
and detailing placed on a rear elevation might not alter the
public perception of the historic form and massing.
Therefore, it is conceivable that a modest addition could be
replicative without changing the resource's historic
character; generally, however, this approach is not
recommended because using the same wall plane, roof line,
cornice height, materials, siding lap, and window type in an
addition can easily make the new work appear to be part of
the historic building. If this happens on a visible
elevation, it becomes unclear as to which features are
historic and which are new, thus confusing the authenticity
of the historic resource itself.
The National Park Service
policy on new additions, adopted in 1967, is an outgrowth and
continuation of a general philosophical approach to change
first expressed by John Ruskin in England in the 1850s,
formalized by William Morris in the founding of the Society
for the Protection of Ancient Buildings in 1877, expanded by
the Society in 1924 and, finally, reiterated in the 1964
Venice Charter--a document that continues to be followed by
64 national committees of the International Council on
Monuments and Sites (ICOMOS). The 1967 Administrative
Policies for Historical Areas of the National Park System
thus states, " . . . a modern addition should be readily
distinguishable from the older work; however, the new work
should be harmonious with the old in scale, proportion,
materials, and color. Such additions should be as
inconspicuous as possible from the public view." Similarly,
the Secretary of the Interior's 1977 "Standards for
Rehabilitation" call for the new work to be "compatible with
the size, scale, color, material, and character of the
property, neighborhood, or environment
."
Conclusion
A major goal of our
technical assistance program is a heightened awareness of
significant materials and the historic character prior to
construction of a new exterior addition so that essential
change may be effected within a responsible preservation
context. In summary, then, these are the three important
preservation questions to ask when planning a new exterior
addition to a historic resource:
1. Does the proposed
addition preserve significant historic materials and
features?
2. Does the proposed
addition preserve the historic character?
3. Does the proposed
addition protect the historical significance by making a
visual distinction between old and new?
If the answer is YES to
all three questions, then the new addition will protect
significant historic materials and the historic character
and, in doing so, will have satisfactorily addressed those
concerns generally held to be fundamental to historic
preservation.
--- NEW EXTERIOR
ADDITIONS TO HISTORIC BUILDINGS ---
Preserve Significant
Historic Materials and Features.
Avoid constructing an
addition on a primary or other character- defining elevation
to ensure preservation of significant materials and
features.
Minimize loss of historic
material comprising external walls and internal partitions
and floor plans.
Preserve the Historic
Character
Make the size, scale,
massing, and proportions of the new addition compatible with
the historic building to ensure that the historic form is not
expanded or changed to an unacceptable degree.
Place the new addition on
an inconspicuous side or rear elevation so that the new work
does not result in a radical change to the form and character
of the historic building.
Consider setting an
infill addition or connector back from the historic buildings
wall plane so that the form of the historic building--or
buildings--can be distinguished from the new work.
Set an additional story
well back from the roof edge to ensure that the historic
building's proportions and profile are not radically
changed.
Protect the Historical
Significance--Make a Visual Distinction Between Old and
New
Plan the new addition in
a manner that provides some differentiation in material,
color, and detailing so that the new work does not appear to
be part of the historic building. The character of the
historic resource should be identifiable after the addition
is constructed.
--------------------------------------------------
NOTE
(1) Roy Worskett, RIBA,
MRTIP, "Improvement of Urban Design in Europe and the United
States: New Buildings in Old Settings." Background Report
(prepared July, 1984) for Seminar at Strasbourg, France,
October, 1984.
Additional Reading
Architecture: The AIA
Journal, "Old and New," November, 1983.
Brolin, Brent C.
Architecture in Context: Fitting New Buildings with Old. New
York: Van Nostrand Reinhold, 1980.
Good Neighbors: Building
Next to History. State Historical Society of Colorado,
1980.
International Council on
Monuments and Sites (ICOMOS). International Charter for the
Conservation and Restoration of Monuments and Sites (Venice
Charter), 1966.
National Trust for
Historic Preservation. Old and New Architecture: Design
Relationship. Washington, D.C.: Preservation Press.
1980.
Rehab Right: How to
Rehabilitate Your Oakland House Without Sacrificing
Architectural Assets. City of Oakland Planning Department.
Oakland, California, 1978.
Ruskin, John. The Seven
Lamps of Architecture. London: George Allen and Unwin, Ltd.,
1925.
Schmertz, Mildred F., and
Architectural Record Editors. New Life for Old Buildings. New
York, Architectural Record Books, McGraw-Hill, 1980.
The Secretary of the
Interior's Standards for Rehabilitation and Guidelines for
Rehabilitating Historic Buildings. Washington, D.C.:
Preservation Assistance Division. National Park Service, U.S.
Department of the Interior, rev. 1983.
First special thanks go
to Ernest A. Connally, Gary L. Hume, and W. Brown Morton, III
for their efforts in establishing and refining our
preservation and rehabilitation standards over the past 20
years. (The "Secretary of the Interior's Standards for
Historic Preservation Projects" constitute the policy
framework of this, and every technical publication developed
in the Preservation Assistance Division.) H. Ward Jandl,
Chief, Technical Preservation Services Branch, is credited
with overall supervision of the project. Next appreciation is
extended to the Branch professional staff, the NPS cultural
programs regional offices, the Park Historic Architecture
Division, and the National Conference of State Historic
Preservation Officers for their thoughtful comments. Finally,
the following specialists in the field are thanked for their
time in reviewing and commenting on the manuscript: Bruce
Judd, AIA, Nore V. Winter, John Cullinane, AIA, Ellen
Beasley, Vicki Jo Sandstead, Judith Kitchen, Andrea Nadel,
Martha L. Werenfels, Diane Pierce, Colden Florance, FAIA, and
H. Grant Dehart, AIA. The photograph of Chicago's Newberry
Library with the Harry Weese and Associates' 1981 addition
was graciously lent to us by David F. Dibner, FAIA, and Amy
DibnerDunlap, coauthors of Buildings Additions Design,
McGrawHill, 1985. The front page "logo" by Nore Winter is a
detail of historic Burns National Bank, Durango, Colorado,
with John Pomeroy's 1978 addition.
Washington, D.C.
September, 1986
|
