Does an older Seattle house need an earthquake retrofit?

Which King County houses usually aren’t anchored

A wood-frame house is light and flexible, and it tends to ride out shaking reasonably well once it’s tied down. The weak point in many older houses is where the wood meets the concrete. In some, the frame simply rests on the foundation, held in place by its own weight and a handful of nails. In others there are bolts, but too few, or there are short stud walls under the first floor that have nothing to stop them from folding sideways.

That describes a lot of the housing in Seattle’s older neighborhoods. Craftsman bungalows and foursquares in Ballard, Wallingford, Ravenna and Green Lake. Tudors on Queen Anne and in Mount Baker. Workers’ cottages on Beacon Hill and in Georgetown. The small houses on West Seattle’s hillsides. Many were built long before bolting and bracing were routine, and some later houses, well into the second half of the last century, were anchored only lightly.

The Eastside has fewer houses of that age, though older blocks near downtown Kirkland, Renton and Kent, and the streets around Front Street in Issaquah, have houses that deserve the same look.

It matters here because Western Washington sits above the Cascadia Subduction Zone and shallower faults, including the Seattle Fault. Nobody can tell you when the next large earthquake will come. What a buyer can do is find out whether the house in front of them has the basic connections.

What to look for in the crawlspace

You don’t need to be an engineer to spot the main signs, only willing to get a little dirty. The crawlspace hatch is usually in a closet floor or behind a small door in the foundation. If you’d rather stay above ground, ask your inspector to photograph what’s described below.

• The sill plate. The flat wooden board lying on top of the concrete foundation wall. Everything else in the house stands on it.
• Anchor bolts. Threaded steel rods rising out of the concrete and through the sill, each with a nut and washer on top, spaced along its length. Retrofit bolts often have larger square washers. Flat steel plates fastened to both the side of the sill and the face of the foundation are another sign of a retrofit.
• Cripple walls. Short stud walls between the top of the foundation and the first floor. They’re common in houses with crawlspaces and on sloping lots, where the downhill side can be tall. Bare studs mean the wall is unbraced. Sheets of plywood nailed to the inside face, with small vent holes cut in them, mean someone braced it.
• Metal connectors. Steel framing clips tying the floor framing down to the sill or the top of the cripple wall.

Several things hide these details. Insulation, ductwork and very low crawlspaces limit what anyone can see. A finished basement covers the sill completely. A general home inspector will report what’s visible and accessible, and a note such as “no anchor bolts observed” is a flag to follow up on. For a clear answer, bring in a structural engineer or a contractor who does seismic retrofits.

While you’re down there, look up. A brick chimney without reinforcement is a separate risk, since it can crack or fall in shaking, and tall brick porch piers deserve the same question. A chimney specialist or the engineer can speak to those.

What a standard retrofit involves

A typical retrofit does a few specific things. New anchors are drilled into the concrete and fastened through the sill, or steel plates are used where there isn’t room to drill from above. Cripple walls are sheathed with plywood nailed in a set pattern, which turns them into braced walls. Metal connectors tie the floor to the sill so the whole frame moves with the foundation.

Most of the work happens from inside the crawlspace, so the living space above is usually left alone. Contractors often add water heater straps while they’re there, and some owners install an automatic gas shutoff valve at the same time; a licensed plumber can advise on that.

A retrofit won’t make a house earthquake-proof. It doesn’t repair a crumbling or badly cracked foundation, and it does nothing about the stability of the ground itself. Hillside houses raise their own questions, which I cover in buying a view home on a steep lot.

Seattle’s prescriptive retrofit permit

Retrofit work is structural, so it’s permitted. Seattle’s Department of Construction and Inspections (SDCI) issues what it calls an Earthquake Home Retrofit Permit, and it publishes prescriptive plan sets for common wood-frame houses: standard details for anchoring the house, bracing the cripple walls and connecting the floor, so a qualifying house can be permitted without hiring a design professional. Homeowners can apply themselves or have their contractor handle it.

The plan sets don’t fit every house. One outside their limits needs a retrofit designed by a structural engineer, which SDCI also permits. SDCI can confirm which path a specific house fits and what the current requirements are.

On the Eastside, the building departments in Bellevue, Kirkland, Redmond, Mercer Island, Renton and Kent each set their own requirements. Call the permit desk and ask whether a prescriptive option applies or an engineer’s design is required.

Whichever city it is, the permit record matters later. A retrofit with a permit and a passed final inspection is documented work that the next buyer’s inspector can confirm.

Retrofits, earthquake insurance and resale

Standard homeowners policies generally exclude earthquake damage. Coverage is usually a separate policy or an endorsement, with its own deductible that is often much larger than the regular one. Some insurers ask whether a house is bolted and braced, and the answer can affect whether and how they’ll write the coverage.

So before your inspection contingency ends, ask your insurance agent two questions about this specific house: whether earthquake coverage is available, and whether a retrofit changes the terms. Ask your lender whether it has any requirement of its own. Don’t buy a house assuming a retrofit brings an insurance discount. Get the answer in writing from the agent.

At resale, keep everything: the permit, the final inspection, the contractor’s invoice and photos of the finished work. A future buyer touring your house will be asking the same questions you’re asking now.

Handling it inside your inspection period

Inspection periods are usually short, and the dates in your purchase agreement don’t move because a contractor is busy. If the general inspection flags missing bolts or unbraced cripple walls, book the engineer or retrofit contractor right away and ask for a written scope and bid.

A seller who agrees to do the retrofit before closing also picks the contractor, and the permit and final inspection then have to fit the transaction’s clock. When time allows, I lean toward a credit or a lower price instead, because the owner who lives with the result is the one choosing who does it. Your lender may limit how a credit can be applied, so confirm the structure with them first. Taking the house as it is and planning the work for later is also a reasonable answer.

In a multiple-offer situation where you’re waiving the inspection contingency, get under the house during the pre-inspection instead. A missing retrofit is a known, priceable item, and on its own it’s rarely a reason to walk away from the right house. My buying page covers how inspections and review periods work here, and older houses often bring a second question with them, which I cover in what knob-and-tube wiring means for a buyer.