We just bought our first house, and the home inspector told us that we should bolt the house to the foundation for earthquake safety. What does this mean? How much should it cost?
Living in CA means that our homes are prone to high seismic activity. Past earthquakes have shown that building practices in homes built before 1980 have a higher risk of sliding off of its foundation. The most practical way to provide seismic resilience to our homes is to undergo a foundation retrofit, not only bolting the house to the foundation, but providing shear resistance to the crawlspace walls with plywood sheathing and additional metal connectors.
There are several reasons we recommend home owners retrofit their foundations. The number one reason is safety. You want to be safe during an earthquake and your home not sliding off its foundation will help keep you safe. Another reasons is so that you have somewhere to go after an earthquake. If you home happens to slide off its foundation, that will force you to relocate. And also because it is way more cost effective to retrofit the foundation before an earthquake than to fix your home afterwards.
Many factors will affect the cost of these retrofits including: the size of your home, number of stories, ease of access to foundation, hillside conditions, slab on grade foundation or raised foundation, unfavorable conditions of your crawlspace/foundation.
For a mid-sized single story home with favorable conditions an average cost could be $4k-$8k but it can easily go up to around $15k depending on the factors stated above. I would recommend looking for a structural engineer that has experience with foundation retrofits that can help you outline your retrofit. Otherwise it will be up to the contractor to recommend how much retrofit your foundation will need, whereas the engineer will have to calculate the minimum retrofit required. Feel free to get at least 3 quotes and compare the prices to how much retrofitting they are recommending.
For additional information, see the following website. Residential Earthquake Retrofitting | Earthquake Safety
Bolting the house to the foundation means to provide connection between your house framing to the concrete foundation. There are hold downs and anchors you may epoxy drill into the foundation. The cost should depend on the locations that structural engineers has designed to be placed those at, and what the finishes are at those locations for you to replace.
retrofit foundation single story house not located in hill side up to 2000 sqf will start from $4,000 not include permits fees and engineering if needed
unfortunately there is no way to tell how much a project like that would cost,
I saw projects that goes up to 130K for foundation work.
i would advice you to call a foundation contractor to give you an estimate and tell you about what you need exactly.
what is the distance between the current bolts? is there any?
do you have cripple walls? are the properly braced?
does your floor joist have all proper connection to cripple wall?
those are just some questions that you can ask.
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Hello Preeta,
The reason why the inspector is insisting on putting bolts for earthquake safety, is because the 2 x 4 frame needs to be bolted to the footing due to the earthquake shakes. The cost should be between $5,000 - $7,000