Historic Building Exterior:
New Additions to Historic Buildings

Compatible New Additions

Although the new addition (right) to this historic library faces the street, it is set back and attached to a secondary, side elevation. A glass hyphen connects and also differentiates the addition from the historic building. The design of the addition reflects, but does not copy, the historic building: it is clearly new. Although it is a sizeable addition, it is compatible in size, scale, design and materials with the historic building. Photo: © David Wakely

A new addition to a historic building 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 exterior addition may be an acceptable alternative.

To meet the Standards, a new addition should:

• Preserve the historic character of the building.
• Preserve the building’s significant historic materials and features.
• Protect the historic significance of the building by making a visual distinction between old and new.

This guidance will help to design a compatible new addition for a historic building that will meet the Standards:

• A new addition should be visually distinguishable from the historic building—a recessed connector can help to differentiate the new from the old.
• A new addition should not be highly visible from the public right-of-way; a rear or other secondary elevation is usually the best location for a new addition.
• The construction materials and the color of the new addition should be compatible or blend with the historic building materials as closely as possible.
• The new addition should be subordinate in size to the historic building; in other words, it should not be too large.

Left: When this large historic residence was converted for office use, an addition (right) was constructed at the rear where it is not visible from the street. It is smaller than the historic building, and its simplified details reference the architecture of the house. A glass connector physically links the addition to the house, but also distinguishes it as new construction. Drawing: NPS files