Foundation contractor —
Seattle & Puget Sound.
Foundations are the only part of the build you can never redo cheaply. We work with licensed structural engineers and follow geotech recommendations to the letter.
Foundations are the only part of the build you can never redo cheaply. We work with licensed structural engineers and follow geotechnical recommendations to the letter — soil bearing capacity, frost depth, drainage, lateral pressure, and seismic detailing for Seismic Design Category D2 (most of Puget Sound).
Foundation work breaks into three categories: new foundations (for additions, ADUs, new construction), foundation repair (settlement, cracks, water intrusion), and seismic retrofit (bolting old houses to their foundations and reinforcing cripple walls).
What we build
SCOPE- 01Stem-wall + slab-on-grade
- 02Helical + push-pier underpinning
- 03Crawlspace conversions
- 04Drainage + waterproofing
- 05Seismic retrofit
- 06Geotech coordination
Phased process
PROCESS- 01
Soils + engineering
Geotechnical report when required, structural engineer designs footings and walls, permit submittal.
- 02
Excavation
Excavate to bearing soil, install dewatering if needed, place compacted gravel base.
- 03
Forms + rebar
Footing forms, wall forms, rebar cages tied to engineer spec, mechanical splices for long bars.
- 04
Pour
Footings first, cure 2–3 days, walls poured next. Concrete tested for slump and air entrainment.
- 05
Waterproofing + drainage
Asphalt-based or membrane waterproofing on basement walls, perforated drain tile at footing, gravel backfill.
- 06
Strip + inspect
Strip forms, fill voids, structural inspection signs off before backfill.
Spec sheet
SPEC- +3,500–4,000 psi concrete with air entrainment
- +#4 / #5 rebar to engineer drawing, 2" cover minimum
- +Anchor bolts at 4 ft OC max, 7" embedment for SDC D2
- +Hold-down anchors (Simpson HDU, MSTC) at shear-wall ends
- +Asphalt emulsion or rubberized membrane waterproofing
- +4" perforated PVC drain tile, gravel-wrapped
- +Closed-cell foam sill seal under bottom plate
Cost drivers
COST- Foundation typeSlab-on-grade $25K–$60K → full basement $80K–$220K for similar footprint
- Soil conditions (rock, poor bearing)+$10K–$60K for over-excavation, piers, or engineered fill
- Underpinning vs full replacementUnderpinning $30K–$120K vs $80K–$250K full replacement
- Seismic retrofit$8K–$35K for typical cripple-wall bolting and bracing
- Dewatering (high water table)+$5K–$25K for pumping during excavation
Codes & permits
COMPLIANCE- IRC R401–R406
Comprehensive footing, foundation wall, and waterproofing code. Includes specific requirements for SDC D2 areas.
- IRC R602.11 (anchor bolts)
Anchor bolts at max 6 ft OC for SDC A-C, 4 ft OC for SDC D2. Most of Puget Sound is D2.
- Seattle SDCI seismic retrofit
City offers permit + inspection program for cripple-wall retrofits with significant fee discounts. Highly recommended on pre-1985 houses.
- Geotech recommendations
Reports often dictate over-excavation depth, fill type, and special inspection. Follow exactly — engineer's seal depends on it.
Is foundation the right call?
- →New construction, addition, or ADU
- →Visible settlement cracks, sticky doors, sloping floors
- →Pre-1985 home without seismic anchor bolts (most Seattle craftsman and post-war houses)
- →Basement water intrusion — waterproofing + drainage replacement
Foundation questions
FAQQ.01
How do I know if I need a seismic retrofit?
If your home is pre-1985 and built on a raised foundation (crawlspace or basement), it almost certainly lacks anchor bolts and braced cripple walls — the two most important earthquake reinforcements. Seattle's Project Impact program subsidizes the work; expect $5K–$25K for a typical retrofit.Q.02
Can you fix foundation cracks?
Hairline cracks (under 1/8") are normal and don't require repair. Active cracks (widening, with displacement) need engineering — often resolved with helical or push-pier underpinning. Polyurethane injection seals water-weeping cracks.Q.03
How long does a new foundation take?
2–5 weeks for a typical single-family foundation: excavation, forms, pour, waterproof, backfill. Weather delays the schedule — concrete needs above-40°F or special heating.Q.04
What about radon?
King County has elevated radon zones in some areas. We install passive radon mitigation (perforated pipe under slab, vent stack) on all new basement and slab-on-grade foundations as best practice. Active fan can be added later if testing shows elevated levels.
Official resources & sources
- Source ↗IRC Chapter 4 — Foundations
- Source ↗WSEC 2021 Residential Energy CodeEnvelope, HVAC, hot-water and air-sealing requirements
- Source ↗WA HB 1110 — Middle housing lawStatewide middle-housing zoning preemption
- Source ↗WA HB 1337 — ADU statewide rulesTwo-ADU baseline, no owner occupancy, parking limits
- Source ↗WA Dept. of Commerce — ADU resources
- Source ↗WA L&I contractor license lookupVerify Golden State ADU Builders Inc · GOLDESA747LZ
- Source ↗Washington State Building Code CouncilStatewide adopted codes (IRC, IBC, WSEC)
Ready to scope your foundation project?
Send a paragraph and the address. A licensed PM replies within one business day with next steps.
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