Standard 4 of the Standards for Rehabilitation states that “Most properties change over time; those changes that have acquired significance in their own right shall be retained and preserved.” Materials, features, and spaces do not need to be original to be considered “historic” and “character-defining.” A property can be significant not only for the way it was originally constructed or crafted, but also for the way it was adapted at a later period or illustrates changing tastes, attitudes, and uses over a period of time. Buildings change over time, and these changes often contribute to a property’s historic significance. If a change is important in defining the property’s historic character, the change should be retained and preserved.
Changes should be carefully evaluated for their relative importance to a property’s overall historic character. A change is not automatically considered to have acquired significance just because it occurred within the property’s period of significance or by virtue of the change’s age (for example, just because a change is more than fifty years old). Also, a change important to the historic character of one building may not be similarly important to the character of another building, and some changes may have little or no historical and architectural merit or may otherwise not be sufficiently important that they have to be retained in order to preserve the overall historic character of the property.
An addition to a school to accommodate growing enrollment may be important when the property is significant for its associations with the history of education in the community. A front porch added to a single-family residence important for its architecture may be significant depending upon when it was added, its architectural character, and condition. An exterior or interior remodeling of a commercial building may be important to the historic character of a building associated with a particular person or with the later commercial development of a neighborhood or area. Some changes may also be important for reasons apart from why the property is otherwise significant. For example, a later structural glass storefront may be important as an example of an architectural style, or a tenant space may be significant for its associations with an important later historic event or use.
Conversely, a later change to a building may not be significant if the property is important as an example of a specific architectural style or the work of a particular architect. An individual storefront change to a multi-storefront commercial building or changes made for a particular use or tenant may not be as important, depending upon the extent to which they contribute to the property’s historic character. A minor addition on the rear or side of a property may not be sufficiently important that it must be retained, and interior changes of a limited impact to the historic character of a property’s important interior spaces, features, and materials may not be significant.
A change needs to be evaluated within the context of the specific historic property, the property’s materials, spaces, and features, and why it is significant to determine the change’s relative importance to the property’s overall historic character and whether the change should be retained and preserved. For contributing buildings in historic districts, a change needs to be evaluated within the context of the historic building itself, as well as the district. Evaluations should be made on the basis of the property’s National Register of Historic Places nomination, if the property is already listed, as well as other documentation, research, and information as needed.
For listed properties, the National Register nomination will describe why the property is significant and will typically identify a period of significance. This stated period of significance should generally be used in evaluating the relative importance of a change to the property and its historic character. Some older nominations, however, may not have a defined period of significance, and other nominations may have an open-ended one. The available National Register documentation may not have addressed the importance of a later change—whether having occurred inside or outside the period of significance—that has acquired significance in its own right. Also, the documentation may not be conclusive, particularly for districts, and supplemental information on the significance of the specific property and change being evaluated may be required. (In some instances a determination that a later change is significant should be reflected in the formal submission of an Additional Documentation form from the State Historic Preservation Office to the National Register or through a Supplementary Listing Record by the National Register staff.)
The relative importance of a change to the historic character of a property remains specific to that individual property, as well as to how it contributes to the district if in a district. Again, a change is not automatically considered to have acquired significance just because it occurred within the property’s period of significance or due to its age.
Wanting to return a property to its original appearance is not adequate justification by itself to remove later changes and may not meet the Standards for Rehabilitation if it requires the removal of later materials, features, or spaces that have acquired significance in their own right. Other times these later changes may not be as important and can be removed without impacting the historic character of the property.
Last updated: October 25, 2022