Home Not Bolted (or Not Properly Bolted) to Foundation
Houses that are not bolted to the foundation can move off their foundations during earthquakes.
How to Identify
- Go down into the crawl space – the area between the first floor and the foundation – to find out if your house is bolted to its foundation.
- Look for 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 Drawings A & B below)
- 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 Drawing B below)
- It is very expensive to lift a house, and place it back on its foundation.
- Homes moving off their foundations can cause gas lines to rupture, which in turn can result in fires.
If your home has no foundation, or an old concrete foundation, see Other Foundation Issues.
- Drill holes through the sill plate into the foundation and install anchor bolts.
- If there is not enough room to drill, you can attach steel plates to hold the sill plate to the foundation.
- Anchor bolts have to be installed properly for them to be effective.
- You must obtain the proper permits from your local Building Department before beginning work.
- Detailed information for do-it-yourselfers or engineers can be found in the International Existing Building Code, published by the International Code Council.
- Publication: How You Can Strengthen Your Home for the Next Big Earthquake in the Los Angeles Area, City of Los Angeles, Department of Building & Safety, October 2001.
NOTE: Slab Foundations
Some homes are built directly on concrete slabs. These houses do not have crawl spaces and cripple walls.
Nearly all homes with slab foundations that were originally built to code will have anchor bolts or straps. However, if the house is not bolted to the slab, you have an earthquake weakness.
Newer homes generally have anchor bolts or straps. If you have an unfinished garage, you may be able to see the anchor bolts.
You are not required to remove siding, drywall or plaster to determine if your house has anchor bolts.
- Home Not Bolted to Foundation
- Cripple Walls
- Post and Pier Foundation
- Unreinforced Masonry Foundations
- Unreinforced Masonry Chimneys
- Steep Slopes
- Unreinforced Masonry Walls
- Roof or Floor Connections with Walls
- Rooms Over Garages
- Mobile Homes
- Soft Stories
- Unique Designs
- Other Foundations