Concrete Foundations in Seattle: Planning Your Quote
Seattle ConcreteCONTRACTORS
(206) 566-0528
Need footings, stem walls or a slab foundation in Seattle? Here’s how foundation work runs, what affects the price, and what we need to quote it.
- Built to stamped plans and inspections
- Footings sized for the soil you actually have
- Drainage and vapor barrier planned in
Get a foundation quote in Seattle
Tell us about the project. We’ll call or email to talk it through.
Concrete Foundations for Seattle properties
Foundation work is concrete where the drawings and the inspector set the rules. For an addition, a detached garage, a backyard cottage (DADU) or a large shed, the plans say how deep the footings go, how much steel goes in, and where anchor bolts and hold-downs sit. Our job is to dig, form, place steel and pour exactly to that plan, and to flag soil or water problems before the concrete goes in.
Craftsman bungalows, Tudors, and mid-century houses with original concrete are common, alongside new townhomes and backyard cottages (DADUs) that need new slabs and walks. We work across Ballard, Wallingford, Queen Anne, Magnolia, Capitol Hill, Beacon Hill, West Seattle, Rainier Valley, Lake City and Northgate.
Additions
Footings and stem walls that tie into an existing house foundation.
Garages and carports
Slab-on-grade with thickened edges, or footings and stem walls.
Backyard cottages (DADUs)
Foundations and slabs for detached accessory units.
Seattle conditions that affect your foundation
Soil and settling
Soils change block to block: dense glacial till on many ridges, softer fill and old wetland soils in lower areas like parts of the Duwamish valley, Interbay and around the lakes. A slab that keeps sinking usually points to a soft or wet base.
Slope and access
Queen Anne, Magnolia, West Seattle, Capitol Hill and the slopes above Lake Washington have steep driveways and stepped yards. Parts of the city are mapped as steep-slope or landslide-prone environmentally critical areas (ECAs), which brings extra SDCI review for grading and walls.
Homes and existing concrete
Craftsman bungalows, Tudors, and mid-century houses with original concrete are common, alongside new townhomes and backyard cottages (DADUs) that need new slabs and walks.
Details that help us price your foundation in Seattle
You don’t need answers to all of these. They’re the questions that shape the design and the price.
Plans
Approved or draft drawings, plus any soils report.
Structure
Addition, garage, ADU, shed or deck.
Site
Photos of the area, slope, trees and access.
Permit status
Applied for, approved or not started.
Schedule
When framing needs to start.
Existing foundation
For additions, photos of the existing foundation where the new one ties in.
Options to talk through
| Type | Good for | Keep in mind |
|---|---|---|
| Slab-on-grade | Garages, sheds, some ADUs | Needs a solid base, vapor barrier and thickened edges |
| Continuous footing + stem wall | Additions and wood-frame houses with a crawlspace | Two-stage pour; matches many older Seattle homes |
| Pier footings | Decks, porches and posts | Sized and spaced per plan |
Permits for concrete foundations in Seattle
Foundations and slabs for additions, garages, backyard cottages and other buildings are part of the SDCI building permit, with footing and steel inspections before the pour. Check SDCI’s permit guide for your address.
Planning a new foundation in Seattle?
Call to talk it through, or send a few details and photos.
What concrete foundations typically cost in the Seattle area
Ballpark numbers help you plan a budget before anyone visits. Use them as a starting point, not a promise.
| Foundation work | Typical range |
|---|---|
| Slab-on-grade (base, vapor barrier, rebar, pour) | $6–$14 per sq ft |
| Continuous footing | $40–$90 per linear ft |
| Stem wall + footing | $80–$150 per linear ft |
| Foundation repair or underpinning | $5,000–$20,000+ per project |
Typical market ranges, not a quote from Seattle Concrete Contractors. These are ranges other Seattle-area concrete contractors publish for this work (Seattle Concrete (seattleconcrete.com) service pages, checked November 2026). Your price depends on size, access, removal, base work, finish and permits, and on conditions at your Seattle property. We give a written quote after we understand the job.
Concrete Foundations in Seattle: quick answers
Do you work from engineered plans?
Yes. Foundations are built to the approved plans and inspected. If you don’t have plans yet, your designer or engineer comes first.
Do I need a permit for a foundation in Seattle?
Foundations for additions, garages, ADUs and most structures are part of the building permit through SDCI.
How long does a foundation take?
Excavation, forming and steel take most of the time; inspection timing and cure time set the rest. Small jobs can be a week or two.
Do I need a permit for concrete work in Seattle?
It depends on the job. SDCI generally requires a grading permit when you add or replace 750 sq ft or more of paving, and walls taller than 4 ft measured from the bottom of the footing need a permit. Anything in the sidewalk, planting strip or driveway apron is right-of-way work that goes through SDOT.
Learn more about concrete foundations
See the full concrete foundations guide, or all concrete services in Seattle.
Tell us about your project
A few photos and rough measurements are enough to start. If you’re not sure what the job needs, describe the problem and we’ll talk it through.
Call (206) 566-0528 or use the quote form at the top of this page.
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Seattle Concrete Contractors | (206) 566-0528 | Seattle, WA