Balancing Seismic Retrofit and Preservation

Reinforcing a historic building to meet new construction requirements, as prescribed by many building codes, can destroy much of a historic building’s appearance and integrity. This is because the most expedient ways to reinforce a building according to such codes are to impose structural members and to fill irregularities or large openings, regardless of the placement of architectural detail. The results can be quite intrusive. However, structural reinforcement can be introduced sensitively. In such cases, its design, placement, patterning, and detailing respect the historic character of the building, even when the reinforcement itself is visible.

Before	Before
After	After

Three important preservation principles should be kept in mind when undertaking seismic retrofit projects:

• Historic materials should be preserved and retained to the greatest extent possible and not replaced wholesale in the process of seismic strengthening;

• New seismic retrofit systems, whether hidden or exposed, should respect the character and integrity of the historic building and be visually compatible with it in design; and,

• Seismic work should be "reversible" to the greatest extent possible to allow removal for future use of improved systems and traditional repair of remaining historic materials.

It is strongly advised that all owners of historically significant buildings contemplating seismic retrofit become familiar with The Secretary of the Interior’s Standards for the Treatment of Historic Properties, which are published by the National Park Service and cited in the bibliography of this publication. These standards identify approaches for working with historic buildings, including preservation, rehabilitation, and restoration. Code-required work to make buildings functional and safe is an integral component of each approach identified in the Standards. While some seismic upgrading work is more permanent than reversible, care must be taken to preserve historic materials to the greatest extent possible and for new work to have a minimal visual impact on the historic appearance of the building.