Are Your Wood Frame Buildings BOLTED to the Foundation?

By:  Cline Agency Insurance Brokers

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How to identify and document for your insurance carrier:

  1. Set your cell phone camera to “Flash On” for photos.

  2. Methodically walk the perimeter of one or more buildings in the complex until you can find an entrance to a crawl space that is easy to access.

  3. Laying on your belly, make your way into the “crawl space” – the area between the first floor and the foundation. Turn to your left and then to your right, looking for evidence the building is bolted. In most cases you’ll immediately recognize the heads of anchor bolts that fasten the sill plate (the wooden board that sits directly on top of the foundation) securely to the foundation. (See Diagrams A & B)

  4. You should be able to see the large nuts, washers, and anchor bolts, installed at least every 4 to 6 feet along the sill plate. Steel plates are sometimes used instead of anchor bolts. (See Diagram B)

Diagram A
Anchor bolts are installed along the sill plate at appropriate intervals.
Diagram B
Steel plates are used alternatively to fasten the sill plate to the foundation

* Source: California Seismic Safety Commission

As you can see from the diagrams, a building’s crawl space may be formed by a cripple wall between the foundation and the floor joists, or the floor joists may rest directly on the sill plate. In either case, you should be able to see the heads of anchor bolts or steel plates installed at appropriate intervals. These fixtures fasten the sill plate to the foundation.

* Source: San Leandro EQ Retrofit Program


Some townhouse developments are built directly on concrete slabs. These projects do not

have crawl spaces and cripple walls. Nearly all buildings with slab foundations that were originally built to code will have anchor bolts or straps. However, if the building is not bolted to the slab, you have an earthquake weakness.

Newer condominium projects (those built after 1950) generally have anchor bolts or straps. If you have an unfinished garage, you may be able to see the anchor bolts.

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