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COST_SPEC / SAMMAMISH

Sammamish ADU Cost: What Homeowners Should Budget For

Real Sammamish, WA pricing for detached and attached ADUs across six lot-size bands. Numbers reflect current bids and recent projects, not internet averages.

Last verified 2026-05-30 · Page in progress — not yet indexed

COST_TABLE / PLANNING ESTIMATES

We're verifying Sammamish's cost data this quarter. Contact us for a current estimate on your specific lot.

Numbers above are planning estimates from current bids and recent Golden State ADU projects on Puget Sound lots — they are not city-published fees. Verify current Sammamish permit and utility fees against the official sources linked below before committing a budget.

FAQ / SAMMAMISH COST

Sammamish ADU pricing questions

  • What does a typical detached ADU cost in Sammamish?

    Sammamish all-in detached ADU pricing varies by lot size and site complexity. Send your address for a same-week range.

    Go deeper: Sammamish ADU cost breakdown

  • What's included in the Sammamish construction line?

    Construction in Sammamish is priced separately from design, permits, and site work so each line is visible.

    Go deeper: Sammamish ADU overview

NAV_GRAPH / Local data

Sammamish resources

CITY_DOSSIER / SAMMAMISH· 47.6163°N 122.0356°W

Built in Sammamish — what we know that the spec sheet won't tell you.

A live dossier from our field PMs: the permit counter, the soils, the bylaw that just changed, and the streets where ADUs are already cash-flowing.

Map · King CountyOpen ↗
Sammamish
Drive-time from yard · ≈ 30 min via I-90© OpenStreetMap contributors
Population67,455
Median lot11,500 sq ft
ADU permits / yr41 (2024)
Build cost band$340–380 / sq ft
Right now in Sammamish
Air quality · US AQI
Source · Google Maps PlatformAffects pour windows + finish schedule
LIVE_INTEL / SAMMAMISH · 6 SIGNALS
Pour-feasibility · todayLoading
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/ 100 · Awaiting feed
  • Weather feed loading
Derived live · Sammamish weather + AQI
Sun rhythm · SammamishDaylight
5:26 AM
9:04 PM
15h 38m daylight
Golden hour · 8:17 PM
98% of June peak
NOAA solar formulas · computed
Moon · cure-week planner—
—
Loading

We track lunar weeks for slab pours — clear nights drop ambient temperature faster, which slows surface curing. Schedule wet slabs midweek under waxing light.

Conway approx · computed
Seismic · 24h within 60 miLoading
USGS earthquake.usgs.gov
On-site clock · Sammamish—
—:—
— · Pacific

Loading. Our standard crew window is 7:00–17:00 weekdays — noise ordinances in most Puget Sound cities allow exterior power tools only inside that band.

America/Los_Angeles · live
Build-rules pulseWithin window
7:00–17:00
Power-tool window · Mon–Fri
—
ADU permits YTD pace
——

Sunday exterior work is restricted in most Puget Sound jurisdictions. We sequence interior trades around it.

Sammamish municipal code · annualized
SPEC_02 / CITY_INTEL

Environmental & locational intelligence

03 / SOLAR_POTENTIAL

Rooftop solar at this address

04 / POLLEN_FORECAST

Tree · Grass · Weed (3-day)

05 / WALK_SCORE

0.5-mile amenity density

06 / NWS_ALERTS

Active NWS weather alerts

LOCATIONAL_INTEL / SAMMAMISH
Drive times from SammamishLoading

Calculating live drive times to four metro anchors…

Real commute time matters for ADU rent comps — and for our crews. We keep installs within a 60-minute radius of our Puget Sound yard.

Data provenance

Drive times pulled live from the Google Routes API (traffic-aware matrix). Each request is timestamped so you can see exactly when the numbers were last refreshed — no stale brochure data.

Google Routes API · traffic-aware
Street view · SammamishLive imagery
Recent Google Street View imagery centered near Sammamish

Lot context matters as much as zoning. We pre-screen access, slope, and tree canopy from imagery before scheduling the site visit.

Google Street View · proxied
Tidal window · SammamishLoading

Waterfront lots: shoreline excavation and barge access windows depend on these. We schedule pours away from extreme low tides when the soils dry unevenly.

NOAA · — mi away
Recent permits · SammamishLoading

Open-data signal of nearby construction velocity — useful for ADU comps and for anticipating examiner workload.

data.seattle.gov · ~3 mi radius
Permit counter · Sammamish
Sammamish Community Development
801 228th Ave SE, Sammamish 98075
Mon–Fri 8:30a–5p
(425) 295-0500Department site ↗
Local zoning quirk

“Tree-retention is the #1 constraint — every >10″-DBH conifer counts. We design footprint AROUND the canopy.”

Sourced from Golden State ADU field PMs · WA Lic. GOLDESA747LZ
Best build window
May → October

Bar shows pour-friendly months · dot marks the current month.

  • Seismic
    SDC D · Issaquah Fault to the south
  • Soil
    Till plateau · seasonal high water-table in low spots
  • Climate
    Plateau gets ≈42″ rain · cooler nights than Bellevue
  • Topography
    Plateau flat; ravine lots steep
  • HOA prevalence
    ≈ 41% — highest in the county
Neighborhoods we build inSee all ↗
Transit signal
ST Express 269 to Redmond + planned Stride routes

Station-area lots earn the largest rent premium in this market.

School signal
Lake Washington School District (LWSD) — top-ranked

Rental yield estimate: $3,100–3,900 / mo — Lake Washington SD premium

Local incentive

Critical-area incentive: ADU bonus FAR when preserving 70%+ tree canopy

Hidden gem

“Klahanie DADUs near the village center pre-lease faster than any city we build in.”

Build cost · Sammamish vs Puget Sound
+$35 vs regional median
$250 / sqftSammamish ≈ $360$425 / sqft
Other cities we hold a permit history in
COST_SAMMAMISH / FULL

Get a full Sammamish ADU cost breakdown — line by line, not a range.

Sammamish's permit fees, soils and design review costs swing 20%+ between blocks. We'll send the breakdown for your specific address, not a citywide average.

  • Sammamish permit + impact fees included
  • Allowance schedule for finishes attached
  • Free 1-pager, no sales call required
Replies within 1 business day
WA Lic. GOLDESA747LZBuilding since 2012
Direct line · Golden State ADU(425) 642-4142

We reply within 1 business day. No spam, ever.

◇ No sales script · No spam · Your details stay with our team