Design-Build & Structural Engineering in Seattle, WA
ECD takes Seattle projects from our Bellevue office, about 10 miles and 20 to 40 minutes away across Lake Washington. Seattle homeowners most often hire us for seismic retrofits of pre-1940 houses, bearing wall removal in Craftsman bungalows and foursquares, and structural engineering for DADUs and basement conversions.
Working with SDCI on a Seattle remodel
Seattle permits are issued by the Seattle Department of Construction and Inspections through the Seattle Services Portal, not through MyBuildingPermit. SDCI distinguishes between simpler permits that can be reviewed quickly and full plan review for larger work. A single beam or a prescriptive seismic retrofit may qualify for a faster path; additions, DADUs and major remodels go through full review with zoning, structural and energy components.
Seattle-specific reviews come up often. Environmentally critical areas, including steep slopes, known landslide areas and liquefaction-prone soils, cover parts of Magnolia, Queen Anne, West Seattle, the Lake Washington shoreline and filled ground near the water. Seattle's tree protection rules apply to significant trees on residential lots. Landmark districts such as Columbia City and the Ballard Avenue area add design review for exterior changes, and Seattle's residential zones have their own lot coverage and height rules for additions and DADUs.
Older Seattle houses and what a remodel has to respect
Much of the Seattle housing we work on was built before 1940: Craftsman bungalows, foursquares, Tudors and early cottages. These houses were framed differently from modern ones. Many use balloon framing, where wall studs run continuously from foundation to roof without a fire block at each floor, which affects both fire safety and how a wall can be modified. Lumber dimensions are often full-size, so modern lumber does not match without shims. Foundations may be early concrete without reinforcement, sometimes with crumbling surfaces.
The most important feature for the engineer is at the bottom of the house. Many pre-1940 Seattle houses stand on short wood cripple walls between the foundation and the first floor, with few or no anchor bolts. That is why we recommend combining any significant structural remodel with a seismic retrofit, and why our engineer always looks at the crawlspace before talking about the kitchen.
Site constraints common in Seattle
- Environmentally critical areas: steep slopes, landslide-prone and liquefaction-prone areas.
- Small lots where lot coverage and setbacks limit additions and DADU placement.
- Landmark districts with design review for exterior work.
- Tree protection for significant trees on residential lots.
- Access and parking on narrow streets, which shape staging and delivery plans.
Projects completed in Seattle
PROJECT · WALLINGFORDCraftsman bungalow bolted and braced on 30-inch cripple wallsEngineered plan, foundation plates, plywood bracing and a braced brick chimney.Seattle neighborhoods we serve
Ballard, Beacon Hill, Capitol Hill, Columbia City, Fremont, Green Lake, Laurelhurst, Madison Park, Magnolia, Montlake, Phinney Ridge, Queen Anne, Ravenna, Wallingford, Wedgwood, West Seattle.
Seattle questions
Remodeling in Seattle: common questions
Do you work in Seattle if your office is in Bellevue?
Yes. Seattle is about 10 miles from our office, and older Seattle houses are where our structural and seismic experience is most useful. We schedule site work to avoid peak bridge traffic and plan deliveries for narrow Seattle streets. Seattle projects are permitted through SDCI rather than the Eastside portal.
What is balloon framing and why does it matter for my remodel?
In balloon-framed houses, common before the 1940s, wall studs run continuously from the foundation sill to the roof. There are no floor platforms interrupting them, so fire can travel inside walls between floors, and floor joists may hang from ledgers on the studs. Remodels add fire blocking and the engineer details any wall changes to respect how floors are supported.
Can I build a DADU on a small Seattle lot?
Often, yes. Seattle's rules allow attached and detached ADUs on most residential lots, with limits on size, height, lot coverage and rear-yard placement. Small lots, steep slopes and large trees can reduce what fits. We check zoning, tree and critical area constraints on your lot first, then design to what is allowed.
Does a Seattle remodel require a seismic retrofit?
Most interior remodels do not require one, but SDCI may require lateral upgrades when you add a story or significantly change walls that resist earthquake forces. Even when not required, combining a retrofit with a structural remodel is cost-effective, because crews, permits and access to the crawlspace are already in place.
How long does an SDCI permit take for a remodel?
It varies with the type of permit and SDCI's workload. Simple structural or prescriptive retrofit permits can be issued relatively quickly, while full plan review for additions and DADUs typically takes several months including corrections. Our Permit Estimator shows typical Seattle ranges, and we track the review throughout.
Free estimate · Bellevue office
Talk to the engineer before you commit to a plan
A site visit, a scope conversation and a written budget range, at no cost.