(a) Properties located within registered historic districts are reviewed by the Secretary to determine if they contribute to the historic significance of the district by applying the following Standards for Evaluating Significance within Registered Historic Districts.

(1) A building contributing to the historic significance of a district is one which by location, design, setting, materials, workmanship, feeling and association adds to the district's sense of time and place and historical development.

(2) A building not contributing to the historic significance of a district is one which does not add to the district's sense of time and place and historical development; or one where the location, design, setting, materials, workmanship, feeling and association have been so altered or have so deteriorated that the overall integrity of the building has been irretrievably lost.

(3) Ordinarily buildings that have been built within the past 50 years shall not be considered to contribute to the significance of a district unless a strong justification concerning their historical or architectural merit is given or the historical attributes of the district are considered to be less than 50 years old.

(b) A condemnation order may be presented as evidence of physical deterioration of a building but will not of itself be considered sufficient evidence to warrant certification of nonsignificance for loss of integrity. In certain cases it may be necessary for the owner to submit a structural engineer's report to help substantiate physical deterioration and/or structural damage. Guidance on preparing a structural engineer's report is available from the appropriate SHPO or NPS WASO.

(c) Some properties listed in the National Register, primarily districts, are resources whose concentration or continuity possesses greater historical significance than many of their individual component buildings and structures. These usually are documented as a group rather than individually. Accordingly, this type of National Register documentation is not conclusive for the purposes of this part and must be supplemented with information on the significance of the specific property. Certifications of significance and nonsignificance will be made on the basis of the application documentation, existing National Register documentation, and other available information as needed. The Keeper may amend the National Register documentation by issuing a supplementary record if the application material warrants such an amendment. If a certification request is received for a property which is not yet listed on the National Register or which is outside a district's established period or area of significance, a preliminary determination of significance will be issued only if the request includes adequate documentation and if there is written assurance from the SHPO that the SHPO plans to nominate the property or district or that the district nomination in question is being revised to expand its significance or for certified districts, written assurance from the duly authorized representative that the district documentation is being revised to expand the significance. Certifications will become final when the property or district is listed or when the district documentation is officially amended unless the significance of the property has been lost as a result of alteration or damage. For procedures on amending listings to the National Register and additional information on the use of National Register documentation and the supplementary record which is contained in National Register Bulletin 19, “Policies and Procedures for Processing National Register Nominations,” consult the appropriate SHPO or NPS WASO.

(d) Where rehabilitation credits are sought, certifications of significance will be made on the appearance and condition of the property before rehabilitation was begun.

(e) If a nonhistoric surface material obscures a facade, it may be necessary for the owner to remove a portion of the surface material prior to requesting certification so that a determination of significance or nonsignificance can be made. After the material has been removed, if the obscured facade has retained substantial historic integrity and the property otherwise contributes to the historic district, it will be determined to be a certified historic structure. However, if the obscuring material remains when a determination of nonsignificance is requested under §67.4(a)(2), the property will be presumed to contribute to the historic significance of the district, if otherwise qualified, and, therefore, not eligible for the other tax credits under section 47 of the Internal Revenue Code.

(f) Additional guidance on certifications of historic significance is available from SHPOs and NPS WASO.