5 Signs Your Home Needs a Seismic Upgrade
The five signs are: the house is older and sits on a crawl space, it has short "cripple walls" between the foundation and the first floor, it has a soft story like an open garage under living space, it's on a hillside or fill soil, and the foundation shows cracks that are growing.
If one or more applies and the house has never been evaluated, it's worth having someone look.
The Pacific Northwest sits near the Cascadia Subduction Zone and on several shallower faults, and the region has felt damaging earthquakes in living memory, including the 2001 Nisqually earthquake. Retrofits target the weak points that cause the most damage in wood-frame houses.
1. The house is older and sits on a crawl space
Many older houses were built before codes required them to be anchored to their foundations. They may look solid, but in strong shaking an unanchored house can slide off its foundation. If you can see the sill plate in the crawl space and there are no anchor bolts through it, that's the first thing to fix.
2. It has cripple walls
A cripple wall is a short wood-framed wall between the foundation and the first floor. Without plywood bracing, these walls can fold over in an earthquake and drop the house. Bracing them with plywood shear panels is a standard part of a retrofit.
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3. It has a soft story
A soft story is a level with large openings and little bracing, like a garage with living space above. That level can't resist sideways forces as well as the rest of the house. Reinforcing it usually takes engineered shear walls or frames.
4. It's on a hillside or fill soil
Hillside houses can face landslide risk during an earthquake, and houses on fill soil can be affected by liquefaction, where loose, wet soil loses strength during shaking. Both call for a structural and often a geotechnical assessment.
5. The foundation has cracks that are growing
Some cracking is normal settling. Diagonal cracks from the corners of doors and windows, stair-step cracks in brick or block, or cracks that keep getting wider deserve a professional look, because they can signal stress that a retrofit should account for.
What a retrofit involves
Foundation bolting
to anchor the sill plate to the concrete.
Cripple wall bracing
with plywood shear panels.
Connection hardware
tying the floor framing to the sill.
Soft-story reinforcement
where it's needed, usually with an engineer's design.
Simple retrofits often use standard prescriptive details, and complex ones need an engineer. Either way, the work is permitted and inspected, and it's all in the crawl space or basement, so you won't see it afterward. More on how we approach seismic work is on our retrofit page.
See every cost before you decide
Tell us what you're planning. We'll set up a free walk-through and send an estimate with every cost listed, so you decide what's in.
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