New Home Construction contractor —
Seattle & Puget Sound.
A custom home is a 12–18 month commitment. We coordinate architect, structural, civil, and trades from feasibility through final walkthrough — one contract, one supervisor, one warranty.
New home construction is the largest, longest, and most consequential project most homeowners ever commission. A custom home in Seattle or the Eastside is typically a 24–30 month commitment from the day you start feasibility to the day you receive a Certificate of Occupancy — roughly 6–10 months of design and permitting followed by 12–18 months of construction. Golden State ADU Builders coordinates that entire program: feasibility, architect liaison, structural and civil engineering, demolition where required, foundation through finish, inspections, and warranty. One contract, one accountable supervisor, one warranty.
We build for three audiences. The first is the homeowner with a lot — inherited, purchased, or part of a teardown play — who wants a purpose-built home designed around how they actually live instead of a 1960s ranch the previous owner left behind. The second is the investor or owner-developer building one new single-family home or duplex on an infill lot for sale or long-term hold. The third is the family doing a near-total addition that crosses the threshold into substantial reconstruction — at which point new-construction sequencing and engineering rigor matter more than remodeling tactics.
The number that surprises most owners is not the cost per square foot — it is the permitting timeline. Seattle SDCI single-family review currently runs roughly 4–10 months depending on intake queue and complexity, with longer runways on lots inside Environmentally Critical Areas, on steep slopes, or where shoreline, tree-protection, or drainage triggers apply. Eastside cities (Bellevue, Kirkland, Redmond, Sammamish, Issaquah) use the regional MyBuildingPermit.com portal and tend to be somewhat faster on conforming SF intake, but city-specific code amendments still apply. We model the permit calendar inside the schedule from day one and quote contracts that reflect the carrying cost of a real review timeline, not a wishful one.
Cost is the other surprise. Delivered cost in the Puget Sound for genuinely custom homes — architect-designed, structurally engineered, built to current Washington State Energy Code with heat-pump primary heat — runs in a wide band based on lot conditions, finish level, and architectural complexity. Steep slopes, rock, poor soils, long utility runs, critical-area buffers, and stormwater detention can each add five- and six-figure line items before framing starts. We deliver fixed-price contracts after the architect's drawings reach roughly a 90% Construction Documents set, not before. Numbers quoted at the schematic stage are estimates, not contracts; treating them as contracts is how owners get hurt.
Golden State ADU Builders is a Washington-licensed and bonded general contractor (license GOLDESA747LZ) with twelve-plus years of Puget Sound residential construction experience. We do not subcontract supervision. Every new home we build has one project manager assigned from contract through warranty close-out, weekly written progress reports, and structured QA milestones documented with photos. That is the construction model. The architecture is yours — designed by your architect, built by us, inspected by the AHJ, warranted by our company.
What we build
SCOPE- 01Architect + engineer coordination
- 02Site work + utilities
- 03Foundation through finish
- 04Smart-home + EV pre-wire
- 05WSEC + Energy Star
- 0610-year structural warranty
Phased process
PROCESS- 01
Lot & parcel feasibility
Survey, geotechnical report, zoning lookup, utility availability check (water, side sewer, power, gas), critical-area screen (steep slope, wetland, stream, shoreline), and a preliminary order-of-magnitude budget. Two to four weeks. Saves owners from buying or building on lots that will not pencil.
- 02
Zoning & code analysis
Read the parcel against the local Land Use Code (Seattle SMC Title 23, Bellevue LUC, Kirkland Zoning Code, Redmond Zoning Code) for height, FAR, lot coverage, setbacks, parking, and tree-protection limits. Output a buildable envelope diagram before the architect starts design.
- 03
Preconstruction budget
After the buildable envelope is set, we work with the architect on a target program, then back-build a preconstruction budget at the schematic stage. Numbers carry contingency until the design tightens.
- 04
Architectural & engineering coordination
We coordinate with your architect (or recommend an independent partner) through schematic design, design development, and construction documents. Structural, civil, mechanical, and energy-code drawings are run in parallel so the permit package is complete on first submittal.
- 05
Permit strategy & submittal
Stamped architectural, structural, civil, energy-code (WSEC), and stormwater drawings submitted via the local AHJ — Seattle SDCI, MyBuildingPermit for Eastside cities, or city-specific portals. Active correction-cycle management to keep the review moving instead of stalling between rounds.
- 06
Site prep & demolition
Tree-protection fencing, erosion-control measures, utility locates, demolition of any existing structure (recycled per local C&D ordinance), and mass grading. On teardown projects we cap utilities, abandon the side sewer per King County rules, and document everything for SDCI inspections.
- 07
Utilities, civil & stormwater
Water service tap, side-sewer extension, electrical service upsize, gas where used, and stormwater infrastructure (detention, dispersion, or infiltration depending on parcel and code). On lots above stormwater thresholds (per the WA Ecology Stormwater Manual), this phase carries real cost and time.
- 08
Foundation
Excavation, footing forms, rebar, waterproofing, perimeter drain, slab and stem-walls poured to engineered specifications. Backfill, compaction, and protected backfill against the foundation wall. Seismic anchorage per the IRC with WA amendments.
- 09
Framing & envelope dry-in
Conventional stick framing or engineered wood (I-joists, LVL, glulam) per the structural set. Sheathing, weather-resistive barrier, roofing membrane and underlayment, windows and exterior doors installed. House is weather-tight typically 3–4 months after framing starts.
- 10
MEP rough-in & inspections
Electrical (200A service typical, EV pre-wire, solar-ready), plumbing (PEX or copper, heat-pump water heater where venting allows), and mechanical (heat-pump primary heat sized per Manual J). Mid-build framing, plumbing, electrical, and mechanical inspections per local AHJ schedule.
- 11
Insulation, air-sealing & energy verification
Continuous exterior insulation, cavity insulation, vapor and air barriers, and a blower-door test to verify air-leakage targets under WSEC. Documentation goes to SDCI / AHJ for energy-code compliance sign-off.
- 12
Drywall, finishes & interiors
Level-5 drywall in feature areas, cabinetry, tile, flooring, finish carpentry, paint, lighting, and appliances. Coordinated with the architect's finish schedule and the owner's selections, with weekly written progress reports throughout.
- 13
Final inspections & handover
Final building inspection, fire/life-safety verification, final mechanical and plumbing inspections, Certificate of Occupancy issuance, blower-door retest if required, owner walkthrough, punch-list close-out, and warranty package. Two-year workmanship, five-year systems, ten-year structural warranty backed by general-liability insurance.
Spec sheet
SPEC- +Heat-pump primary heat (Mitsubishi, Daikin, Trane) sized via Manual J load calculation
- +Heat-pump water heater or condensing gas tankless where venting and code permit
- +200A electrical service standard, EV charging rough-in to garage, solar-PV-ready conduit
- +High-performance fenestration (Marvin, Pella, Andersen) — typically dual-pane low-E with selective triple-pane
- +Continuous exterior insulation + advanced air sealing to meet WSEC blower-door target
- +Structured low-voltage wiring (Cat-6, fiber where requested, mesh Wi-Fi backhaul)
- +Standing-seam metal or 50-year architectural composition roofing with synthetic underlayment and ice-and-water shield at penetrations
- +Engineered structural elements (LVL, I-joists, glulam) per stamped structural drawings
- +Continuous foundation drain, capillary break, and dampproofing per IRC R406
- +Code-compliant residential fire sprinklers where required by the local AHJ (Washington-specific amendment in certain jurisdictions)
- +Hard-wired interconnected smoke and CO alarms per WA RCW 19.27.530 in all sleeping areas and on every floor
Cost drivers
COST- Lot conditions (slope, soils, rock)Steep slopes, rock, glacial till, or expansive soils can add tens of thousands to hundreds of thousands in foundation, retaining, and excavation versus a flat clean lot. A geotechnical report at feasibility is the cheapest insurance on a custom build.
- Demolition of an existing structureTeardown adds demolition labor, asbestos and lead testing (often required for pre-1978 homes), side-sewer abandonment, utility caps, and C&D recycling fees on top of the new build budget.
- Utility extensions & service upsizesLong water/sewer runs (>50 ft), new side-sewer to the main, electrical service upgrades, and new gas service can each add five-figure line items. Distance to the public main matters.
- Stormwater detention & critical areasLots over impervious-surface thresholds (see the WA Ecology Stormwater Manual for Western WA), or inside Environmentally Critical Areas, can require detention vaults, dispersion trenches, or geotech-engineered stormwater systems that add cost and review time.
- Architectural complexityCathedral ceilings, cantilevers, walls of glass, complex roof intersections, and non-orthogonal plans add framing labor, engineering, and finish hours. Compact rectangular plans build cheapest per square foot.
- Finish levelIdentical square footage can swing widely depending on cabinetry tier, counter selection, tile package, appliance package, plumbing fixtures, lighting, and millwork. Owners control this dial more than any other.
- Permit and carrying cost during reviewA 6–10 month permit review means six to ten months of property tax, debt service on land or construction financing, and project-management cost before a single nail is driven.
- Smart home, security, AV, and low-voltageWhole-home integration (lighting control, audio, security, network) can be a meaningful line item if specified after rough-in; better to plan in at structured-wiring.
- Solar PV, battery storage, EV chargingPV systems, batteries (Tesla Powerwall, Enphase), and Level-2 EV chargers are commonly added at construction; cost depends on roof area, panel count, and inverter strategy.
- Site access and staging constraintsNarrow streets, no on-site staging, tight neighbor proximity, and city-required traffic-control plans can add labor and equipment-rental cost on certain urban lots.
Codes & permits
COMPLIANCE- Washington State Energy Code (WSEC) — Residential
Statewide energy code adopted by the WA State Building Code Council. Requires continuous insulation, advanced air sealing, heat-pump primary heat in most new construction, and blower-door verification of envelope air-leakage. Authoritative source: sbcc.wa.gov.
- International Residential Code (IRC) + Washington amendments — RCW 19.27
Statewide adoption of the IRC governs single-family and duplex new construction. The Washington legislature codifies adoption and amendments in RCW 19.27.
- Seattle SDCI Tip 311 — Single-Family Residence Permits
Defines Seattle's required submittals, intake routes, and review steps for new SF homes. Authoritative source for any Seattle SF permit claim on this page.
- Seattle Land Use Code — SMC Title 23
Governs zoning, lot coverage, FAR, height, setbacks, and tree-protection across Seattle. The buildable envelope is set here long before architectural design begins.
- WA Ecology Stormwater Manual for Western Washington
Governs new and replaced impervious-surface thresholds and required stormwater BMPs. Many redevelopment lots cross these thresholds, which triggers civil engineering scope.
- Smoke & CO alarms — RCW 19.27.530
Hard-wired interconnected smoke alarms required in all sleeping areas, outside sleeping areas, and on every floor; CO alarms outside each sleeping area. Verified at final inspection.
- King County side-sewer abandonment & capacity charge
Existing side sewers must be properly abandoned at the main on teardown projects; new connections to the King County system can trigger a 15-year monthly Capacity Charge that should be budgeted at permit.
Is new home construction the right call?
- →You own a buildable lot — purchased, inherited, or part of a teardown — and want a purpose-built home instead of an off-the-shelf floor plan
- →Your existing house is functionally obsolete (1940s–1970s ranch with bad layout, undersized systems, low ceilings, and no path to a usable remodel)
- →You are doing an addition so large it crosses into substantial reconstruction and needs to be sequenced like new construction
- →You are an investor or owner-developer building a single new SF home or duplex on an infill lot for sale or long-term hold
- →You want to maximize lot value through a high-quality custom build that resells at a top-of-market price
- →You are building a multi-generational home on family land and need design coordination plus accountable construction
New Home questions
FAQQ.01
How long does it take to build a custom home in Seattle?
From contract to keys is typically 12–18 months of construction once the permit is issued. Before that, expect 3–6 months of design and 4–10 months of permit review, depending on jurisdiction and complexity. Total clock from feasibility kickoff to move-in is most often 24–30 months. We sequence the architect, engineers, civil, and permitting in parallel where possible to keep that clock honest.Q.02
What does a new custom home cost in the Puget Sound?
Delivered cost varies widely by lot, finish, and complexity. Lot conditions (slope, soils, demo, utilities, stormwater), architectural complexity, and finish-level selections are the three biggest variables. We quote fixed-price contracts only after design reaches roughly a 90% Construction Documents set; numbers quoted at schematic stage are estimates carrying contingency, not contracts. We are happy to walk through a budget range for your specific lot during the feasibility conversation rather than publishing a single price per square foot that mis-sets expectations.Q.03
Do you do design-build, or do I hire my own architect?
We work with independent architects — your choice or someone we recommend — rather than holding the design role in-house. This protects design quality, gives you wider architectural options, and keeps a healthy second set of eyes on the construction. We carry the construction, project management, permit liaison, and warranty.Q.04
What permits are required for a new single-family home in Seattle?
At minimum: a building permit (SDCI), separate mechanical, plumbing, and electrical permits, a side-sewer permit, often a stormwater review, and possibly tree-protection and grading permits. Lots inside Environmentally Critical Areas, on steep slopes, or with shoreline access trigger additional reviews. We manage the full submittal and correction-cycle process via SDCI; the authoritative source is SDCI Tip 311, linked in our official sources below.Q.05
Can you build to Passive House or net-zero standards?
Yes. WSEC is our baseline for every new home; Passive House certification and net-zero (PV-offset) configurations are available as upgrades with documented premium over baseline cost. The biggest variables are window package, mechanical strategy (ERV/HRV sizing), and PV/battery system sizing.Q.06
What about tear-down-and-rebuild — can you handle the whole project?
Yes. Teardown projects add demolition, asbestos and lead testing where the existing structure pre-dates 1978, side-sewer abandonment, utility caps, C&D waste recycling per the King County or city ordinance, and re-establishment of all utilities. We sequence demo and new-build permits so the lot does not sit unused longer than necessary.Q.07
Do you build duplexes and small infill multifamily?
Yes for duplexes on parcels where zoning allows. For three-unit, four-unit, cottage cluster, or townhouse projects, see our Small Residential Development page — those projects use a different permit pathway and have their own feasibility, civil, and platting considerations.Q.08
What warranty do you provide on a new home?
Two years on workmanship, five years on installed systems, ten years on structural elements. Backed by $2M general-liability insurance and our Washington general contractor's license and bond. Warranty package is delivered at handover with the maintenance schedule and emergency contact information.
SOURCE_LAYER / Official citations
Where these claims come from
Permit, code, and middle-housing statements on this page are sourced to the official publishers below. Click any title to read the primary document. Dates indicate when each URL was last hand-verified by an editor.
- New Single-Family Residence Permits — SDCI Tip 311
Required permits, intake routes, and review steps for new single-family homes inside Seattle.
Seattle Department of Construction & InspectionsVerified 2026-06-08 - Seattle Municipal Code — Title 23 Land Use Code
Lot coverage, height, FAR, setback, and zone definitions referenced in feasibility work.
City of Seattle / MunicodeVerified 2026-06-08 - Washington State Energy Code (WSEC) — Residential
Statewide energy-code requirements (envelope, blower-door, heat-pump primary heat) that apply to all new homes.
Washington State Building Code CouncilVerified 2026-06-08 - Washington State Building Code (RCW 19.27) — IRC Adoption
Statewide adoption of the International Residential Code with Washington amendments governing new SF construction.
Washington State LegislatureVerified 2026-06-08 - Residential Building Permits — City of Bellevue
Bellevue residential permit categories, review tracks, and submittal requirements for new homes and additions.
City of Bellevue Development ServicesVerified 2026-06-08 - MyBuildingPermit.com — Regional Permit Portal
Shared electronic permit submittal portal used by most Eastside cities; basis for the permit-submittal process.
eGov Alliance (Bellevue, Bothell, Issaquah, Kenmore, Kirkland, Mercer Island, Redmond, Renton, Sammamish, Snoqualmie, Woodinville)Verified 2026-06-08 - Building & Construction Permits — City of Redmond
Redmond residential building permit process for new homes and major remodels.
City of RedmondVerified 2026-06-08 - Building Permits — City of Kirkland Planning & Building
Kirkland Permit Center intake process used for single-family and duplex new-construction reviews.
City of KirklandVerified 2026-06-08 - Seattle SDCI Fee Schedule — Building Permits
Permit-fee structure homeowners should budget alongside the build cost.
Seattle Department of Construction & InspectionsVerified 2026-06-08
This page is informational, not legal advice. Specific land-use, permit, or HB 1110 questions about a particular parcel should be directed to the appropriate AHJ or a Washington-licensed attorney.
Official resources & sources
- 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)
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INTERNAL_LINKS / Deep Map