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.
 Two historic commercial buildings were successfully joined as part of a larger rehabilitation project. The glass connector detail is shown below. Photo: Martha L. Werenfels, AIA. |
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
 This small glass connector between two historic buildings is appropriately set back. This approach meets the Standards for Rehabilitation. Photo: Martha L. Werenfels, AIA. |
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 above-ground 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.
"New Exterior Additions to Historic Buildings" an Historic Preservation Brief
