Additions to Historic Buildings
Preservation experts from the National Park Service recommend the following steps in restoring any historic structure. First, identify the historically significant features. Second, protect the features that are historically significant. Third, repair damage to historically important features. Fourth, replace what cannot be repaired. Fifth, recreate missing features that were historically significant. And lastly, avoid new additions that alter the historical appearance inside, or outside.
New additions should be considered carefully. This story is divided into three sections: Introduction; Recommended considerations for new additions to historic buildings; and Not Recommended, a list of actions that could damage or destroy the historic significance of a building. All recommendations come from the U.S. Department of Interior's Standards for Rehabilitation of Historic Buildings.
Additions to historic buildings: an introduction
An attached exterior addition to a historic building expands its "outer limits" to create a new profile. In this photo, a compatible building has been added to the rear elevation of an historic building. 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 resource.
A cautionary note: Although the work in this section is quite often an important aspect of rehabilitation projects, it is usually not part of the overall process of preserving character-defining features (identify, protect, repair, replace). Additions must be assessed for their 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 constructing a new addition.
Recommended considerations for additions to historic buildings
Place functions and services required for the new use in interior spaces, which are not character-defining, rather than installing a new addition.
Construct 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 destroyed.
Locate the attached exterior addition at the rear or on an inconspicuous side of a historic building; and limit its size and scale in relationship to the historic building.
Place new additions such as balconies and greenhouses on non-character-defining elevations and limit and size and scale in relationship to the historic building, as in the photo, above. The small glass connector between two historic buildings has an appropriate setback.
Design new additions in a manner that makes clear what is historic and what is new.
Consider 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.
Design additional stories, when required for the new use, that are set back from the wall plane and are as inconspicuous as possible when viewed from the street.
The contemporary addition (above, left) to historic library is appropriately placed on secondary side elevation.
In the photo at right,the historic character of the streetscape has been changed by additions to the rooftop and bay.
Do Not:
- Expand the size of the historic building by constructing a new addition when the new use could be met by altering non-character-defining interior space.
- Attach a new addition so that the character-defining features of the historic building are obscured, damaged, or destroyed.
- Design a new addition so that its size and scale in relation to the historic building are out of proportion, thus diminishing the historic character.
- Duplicate 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 building.
- Imitate a historic style or period of architecture in new additions, especially for contemporary uses such as drive-in banks or garages.
- Design and construct new additions that result in the diminution or loss of the historic character of the resource, including its design, materials, workmanship, location, or setting.
- Use 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.
- Design new additions such as multi-story greenhouse additions that obscure, damage, or destroy character-defining features of the historic building.
- Construct additional stories so that the historic appearance of the building is radically changed.
In the photo above, the rooftop addition dramatically changes the appearance of this historic building.
To see a list of all of the stories in this series, click here.
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