Bracing and bolting walls costs anywhere from $550 to $7,000 or more, depending on how it’s done. The methods vary depending on the architecture of your home. Let’s explore four common retrofit methods, as well as a fifth task that’s important for any seismic retrofit:
Anchoring a Mudsill
Anchoring a mudsill costs between $1,000 and $3,000. This process places anchor bolts through the mudsill—also called a sill plate—and into the stem or cripple wall. This technique is common in homes with brick foundations or crawl spaces and is meant to prevent the wall and mudsill from slipping off the foundation.
Cripple Shear Wall Bracing
Bracing cripple shear walls costs between $1,000 and $2,500. This process uses plywood sheathing and 2-by-4 blocking to reinforce the cripple wall. Cripple walls are short walls that close off the crawl space in your home. Older homes are prone to collapsing during earthquakes when they aren’t braced.
Cripple Wall Bolting
Bolting cripple walls costs between $1,000 and $3,000. Instead of anchoring to a mudsill, the crawl space walls are bolted to the floor above. This process still involves bracing cripple walls.
Universal Foundation Plate
Universal foundation plate (UFP) retrofitting costs between $550 and $1,500. The plates alone go for about $20 each. This is the most basic earthquake retrofit you can do to your home.
Earthquake Valve InstallationÂ
Installing an earthquake gas shutoff valve costs around $250 to $750, with most homeowners paying around $350. The four preceding tasks involve methods of bracing and bolting, but this task is separate and often required for home sales. Some cities even require and charge for inspections.
Earthquake gas shutoff valves themselves run from $100 to $250, or $500 to $1,500 or more for commercial-grade earthquake valves.
Seismic Retrofit Costs by Foundation Type
The foundation type upon which your home sits can affect the overall earthquake retrofit cost. Slab foundations are the most affordable for retrofitting (as low as $550), while brick, post and pier, and wood foundations can all lead to a seismic retrofit cost of $10,000 or more.