Preservation Challenge: Additions

Historic rehabilitation projects alter a historic building to house a new use. In some cases, this new requires more square footage than the historic building has available. In these instances, it may be possible to construct an addition while still maintaining the integrity of the historic building. The National Park Services states that a successful addition to a historic building should be “compatible but different” than the original structure. What comprises a compatible addition is subjective and often debated in historic preservation discourse. However, the National Park Service does provide some guiding principles.

Minimize visibility

The new addition should be minimally visible when viewing the building from primary vantage points. In most cases, this will mean that the addition should be located on rear or side elevations, however, even these locations can be inappropriate for an addition if the building is visually prominent on multiple sides.

Use site elements to obscure the addition. Features such as vegetation or grade changes can screen the addition from view.

Preserve historic material 

Preserve significant site features including vegetation, grading, walls, fences, walkways, driveways, and archeological resources when constructing an addition.

Minimize demolition of historic material by connecting the addition to the historic building through an existing door or window opening.

Avoid removing or obscuring significant historic features on the exterior or interior.                                                                                                                                                                     

Keep the addition subordinate

The size, scale and massing of addition should be subordinate to the historic building. In most cases, this will mean that the addition is smaller than the historic building in height and footprint.

Separate the addition from the historic building with a small hyphen or break in the massing of the building.  

Step the façade of the addition back from the face of the historic building.

Design a “different but compatible” addition

Avoid any approach that unifies the massing of the addition with the historic building – the addition should be a distinct, subordinate element. The volume of the original building should be discernable.

Use building materials in the same color range as the historic building. Do not use materials that have a high contrast to the historic materials.

Base the size, rhythm and alignment of the addition’s windows and doors on the historic windows and doors.

 Respect the architectural expression of the historic building type. For instance, a residential building should have an addition with features typical of a residential buildings, not another building type, such as and industrial building or commercial building.

Successful additions to historic buildings can be a challenge. It is always a good idea to engage with an architect who has experience designing additions to historic buildings before embarking on a project. For more information about compatible additions to historic buildings, see Preservation Brief 14: New Exterior Additions to Historic Buildings: Preservation Concerns.