Changing Secondary Interior Spaces in Historic Buildings

Secondary interior spaces are less critical in defining a building’s importance than the primary spaces. They often still help define the building’s significance and character, but because of their size, location, or function their impact is not felt as strongly when moving through the building. Altering these spaces may not significantly impair the ability of the overall building to convey its primary historic significance. (Refer to Identifying Primary and Secondary Spaces in Historic Buildings for more information.) Therefore, secondary spaces offer more opportunities for change and alteration compared to what is allowed in primary spaces. Appropriate changes may range from removal of existing partitions and addition of new partitions, to insertion of new floors, cutting openings in existing floors or ceilings and other modifications depending on the location and condition of the space. The opportunities and limitations for change must be identified within the following context.

Spaces may be subdivided both vertically through the insertion of new walls or horizontally through the insertion of new floors or mezzanines. New vertical or horizontal divisions must not intersect or alter the interior or exterior appearance of existing windows, doors, or other architectural features, especially when these changes can be seen from primary spaces or visible exterior elevations. Even if secondary spaces are subdivided, historic architectural features and finishes that contribute to the character of the space should be retained.

Secondary spaces that have been previously modified and lack important architectural features or finishes allow greater opportunity for change. New modifications must not alter the historic character of the space. New treatments that require removing all existing finishes, whether historic or not, and exposing structural elements in buildings where this is not in keeping with the historic appearance of the property’s interior are not appropriate. Conversely, creating highly decorated or elaborate interior rooms and spaces in buildings that were historically devoid of such features is also not appropriate.

New floor openings must generally be contained within secondary spaces and be of a limited size. New stairs to provide a secondary means of egress may be placed within secondary spaces. However, a new floor cut must be placed away from exterior walls, particularly if there are windows and other openings in the wall through which the new floor cut would be visible from a public right-of-way. In addition, floor cuts should leave portions of the floor in place around the new openings and should appear as cuts into existing floors, not as a wall-to-wall removal of floor material that leaves a gap in the floor across the building.

In general, secondary spaces provide opportunities for change necessary to convert a building to a new use while maintaining its overall architectural character in accordance with the Secretary of the Interior’s Standards for Rehabilitation.

Additional guidance »


Last updated: September 15, 2022