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Wood framing for a large two-story custom home with arched window openings and a tower element

Seismic Retrofitting

Cripple Wall Bracing

The short wood walls under an older house are its weakest link in an earthquake. Bracing them with structural panels keeps them from folding over.

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Cripple Wall Bracing

A cripple wall is a short wood-framed wall that sits on top of the concrete foundation and holds up the first floor of a raised-floor house. In many older houses, those walls are just studs with exterior siding or stucco on the outside. In a strong earthquake, they can rack sideways like a parallelogram and collapse, dropping the house onto the foundation or the ground.

Bracing turns the cripple walls into shear walls. Structural plywood or OSB panels are nailed to the inside face of the studs on a set pattern, with blocking and connections that transfer the force from the floor above, through the panels, into the foundation. Combined with foundation bolting, it is the core of a residential seismic retrofit.

How bracing is installed

We work from the crawlspace, so the rooms above are not disturbed. Panels are cut to fit between the sill plate and the top plate of the cripple wall, and nailed along every edge and into intermediate studs on the spacing the plan requires. Blocking is added where panel edges need backing. The amount and location of bracing depends on the house size, the number of stories and the plan being followed.

  • Structural panels

    Plywood or OSB rated for shear, nailed on the specified pattern.

  • Ventilation holes

    Holes cut in the panels between studs so the crawlspace stays ventilated and can be inspected.

  • Connections above

    Framing clips or blocking that tie the floor framing to the top of the cripple wall.

What has to be sound first

Bracing only works if the wood it is nailed to is sound. Rotted or termite-damaged sill plates and studs are replaced first. If the foundation concrete is crumbling or the cripple walls are taller than 4 feet, the house needs an engineer rather than the standard plan.

Bracing and bolting together

Bracing keeps the cripple walls from collapsing; bolting keeps the house from sliding off the foundation. One without the other leaves a weak point, so the standard retrofit does both. See our foundation bolting page for the other half.

From our clients

Real Google reviews from LE Construction clients, quoted word for word.

EXCELLENT

5.0 out of 5, based on 17 Google reviews

  • Diana White

    February 2022 · Google review

    "Very professional , responsive, and knowledgeable- installed earthquake retrofit for my house."
  • Shawn Whelan

    April 2024 · Google review

    "Luis and Fernando were great to work with all the way through on our Foundation Retrofit. Luis took the time to set up extra meetings and ensure the entire job was done correctly, quickly, and at a great price. He also took charge of all permits and navigating the EBB process to ensure we got our State refund check."

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Brace the weak link

Let us look under your house. We will tell you whether the cripple walls are braced and what it would take.

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Cripple Wall Bracing: FAQs

How do I know if my house has cripple walls?

If your house has a crawlspace and the first floor is several steps above the ground, there are probably short walls between the foundation and the floor. Looking into the crawlspace access usually shows them. Some older houses have no cripple walls, with the floor framing sitting directly on the foundation, and those need bolting but not bracing.

Will bracing block ventilation in my crawlspace?

It should not. Bracing panels are installed with ventilation holes between the studs, and existing foundation vents are left open. Crawlspace ventilation helps keep the wood dry, which protects the retrofit and the rest of the house.

Can cripple walls taller than 4 feet be braced?

Yes, but not with the standard prescriptive plan. Taller walls, often found on sloped lots, need an engineered design that accounts for their height and the loads. We coordinate the engineering, and the grant program does not cover these houses.

Does bracing go on the inside or the outside of the wall?

Almost always on the inside face, working from the crawlspace, so the exterior siding or stucco does not have to be removed. In some cases with limited crawlspace access, an exterior approach is used, which affects the siding and cost.

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