Historic Structures

Historic structures present unique problems for the safety assessment process. Most people agree that older structures are vulnerable to earthquake damage. However, the actual damage (not potential damage) to a building is the main factor used to determine continued occupancy after a disaster.

This is not to say that you should not consider vulnerability; it simply means that you should focus on observable damage. Potential for additional damage (as from aftershocks) should temper the posting decision.

The URM Dilemma

In the building industry, it is common knowledge that:

Unreinforced masonry (URM) that has not been strengthened is a collapse hazard.

The potential for collapse can be significantly reduced when the building has been strengthened and proper anchorage has been installed.

An unstrengthened building is technically unsafe prior to a disaster. However, this knowledge should not influence a post-disaster safety evaluation. If an unstrengthened building is undamaged by an event, it is as "safe" after the event as it was prior to the event. The older building will not be posted with restrictions or as unsafe simply because it is old.

After a disaster such as an earthquake, older buildings often pose falling hazards and may be vulnerable to collapse, especially from aftershocks. Click the links below for a closer look at the details and concerns about historic structures.

What is a historic building?

Stabililization and Shoring

Examples of historic structures