Preservation as a Treatment: The Interior Secretary's Standards for Historic Properties

The Secretary of the Interior's Standards for the Treatment of Historic Properties describe four approaches to historic buildings: preservation, rehabilitation, restoration and reconstruction. This page explains preservation. (Summary; the official standards and guidelines govern.)

What preservation means

Preservation is applying the measures needed to sustain a historic property's existing form, integrity and materials. The work, including first steps to protect and stabilise a property, generally focuses on the ongoing maintenance and repair of historic materials and features rather than extensive replacement or new construction. New exterior additions fall outside this treatment, but limited, sensitive upgrades to mechanical, electrical and plumbing systems, and other code-required work to keep the property usable, are appropriate.

The eight standards for preservation

1. Use. A property keeps its historic use, or gets a new use that keeps as much as possible of its distinctive materials, features, spaces and spatial relationships. Until a treatment and use are decided, it is protected and, if needed, stabilised.
2. Character. Its historic character is kept; replacing intact or repairable historic materials, or altering characteristic features, spaces and spatial relationships, is avoided.
3. A record of its time. Each property is treated as a physical record of its time, place and use. Work to stabilise, consolidate and conserve historic materials is physically and visually compatible, identifiable on close inspection, and documented for future research.
4. Later changes. Changes that have gained historic significance of their own are kept.
5. Craftsmanship. Distinctive materials, features, finishes, construction techniques and craftsmanship are preserved.
6. Repair. The condition of historic features is assessed to decide how much intervention is needed; where deterioration calls for repair or limited replacement of a distinctive feature, new material matches the old in composition, design, colour and texture.
7. Gentle treatments. Any chemical or physical treatment uses the gentlest effective means; damaging treatments are not used.
8. Archeology. Archeological resources are protected and preserved in place; if they must be disturbed, mitigation is carried out.

When to choose preservation

Preservation fits when the goal is to keep the building as it exists now, including later changes and additions, not only the original fabric. It may mean simply maintaining what is there or more extensive repair, but protection, maintenance and repair come first and replacement is kept to a minimum.

Consider it when:

• the property's distinctive materials, features and spaces are essentially intact and convey its significance without extensive repair or replacement;
• showing it at a particular period is not appropriate;
• a continuing or new use does not need additions or extensive alterations.

Before work begins, a documentation plan for preservation should be prepared.

Further reading

• The Standards … with Guidelines for Preserving, Rehabilitating, Restoring & Reconstructing Historic Buildings: introduction, preservation and rehabilitation and restoration and reconstruction (PDF)
• The standards for the treatment of historic properties · other guidelines for applying them · their history
• For tax-credit projects: rehabilitation standards and planning successful rehabilitation projects

Sources

• National Park Service, "The Secretary of the Interior's Standards for the Treatment of Historic Properties: Preservation as a Treatment and Standards for Preservation." https://www.nps.gov/articles/000/treatment-standards-preservation.htm