Lynnwood ADU FAQ
Real, locally-grounded answers about building an accessory dwelling unit in Lynnwood, WA — from someone who pulls Lynnwood permits every month. Permit windows, zoning, cost ranges, rent comps and incentives, all current to 2026.
- Permit window
- 8–12 wk
- Min lot size
- 5,000 sqft
- Cost index (Seattle=1.00)
- 0.91×
- Neighborhoods covered
- 6
Building an ADU in Lynnwood — answered
Can I really build two ADUs near the Lynnwood light-rail station?
Yes within the Station Area Overlays defined in the 2024 LMC update. Density bonuses include reduced setbacks and a 30 ft height allowance.
What are the ADU impact fees in Lynnwood?
Combined transportation, parks and school impact fees run $8–11K outside the SAO; inside the SAO they're discounted ~40%. Garage conversions are exempt from school impact fees.
Will I need an Alderwood Water connection fee?
Yes if the property is in AWWD service area — typically $4–7K for ADU water/sewer general facilities charges. We confirm purveyor at feasibility.
What does an 800 sqft DADU cost in Lynnwood, WA?
Based on our 2024–2025 bid archive, an 800 sqft detached ADU in Lynnwood lands at $420k–$525k all-in — design, permits, site work, construction, and utilities. A 600 sqft AADU (converting interior space + adding a separate entry, kitchen and bath) typically runs $230k–$305k, and a clean garage conversion lands at $125k–$180k. The variance inside each range comes from foundation type, slope, side-sewer condition, and finish level.
How long does the Lynnwood permit process actually take?
Plan on 8–12 wk for plan review once we submit a complete package. Pre-application work (zoning verification, site survey, soils report when ECA is in play, energy calcs) adds another 4–6 weeks before submittal. The cities that move fastest are the ones with a pre-approved plan program; Lynnwood's typical path is moderate for the Puget Sound.
What zoning rules apply to ADUs in Lynnwood?
RS-7 / RS-8 / RML — ADU + DADU permitted under LMC 21.42. Minimum lot size is 5,000 sqft. The biggest constraints we plan around are: Wetlands and Class IV streams cover Cedar Valley and Martha Lake basins; Some Alderwood Manor blocks still on Alderwood Water & Wastewater District — separate ADU connection fees apply. We pull GIS, zoning, and overlay data for your specific parcel during the feasibility step so we don't design something the permit reviewer will reject.
Can I rent the ADU in Lynnwood as short-term (Airbnb)?
Washington HB 1337 removed the statewide owner-occupancy requirement, but short-term rental rules are set city-by-city. In Lynnwood, you'll want to confirm whether the city requires an STR license, caps the number of STR units per host, or restricts STRs to the owner's primary residence. Long-term rental (30+ day leases) is allowed without any STR-specific licensing in every city we cover.
Go deeper: Read: Long-term vs. short-term rental ADU in Seattle
What rent can I expect from a new ADU in Lynnwood?
Current comps for a new-construction 1-bedroom (500–750 sqft) in Lynnwood sit around $2,150/mo. A 2-bedroom (750–1,000 sqft) runs ~$2,800/mo. Yields are best on 1-bedroom units near transit corridors; 3-bedroom units are rare and command a premium but only when zoning allows a 1,000–1,200 sqft DADU.
Do I need a separate utility meter for the ADU in Lynnwood?
For a DADU, yes — separate power and water meters are standard, financeable, and what lenders expect. For an AADU or garage conversion, meters are usually shared with the primary home and tenants are billed via a RUBS (Ratio Utility Billing System) addendum to the lease. We coordinate the utility tap, meter installation, and PSE/SCL/SPU paperwork as part of the build.
What incentives or fee waivers are available in Lynnwood?
Station Area Overlay impact-fee discounts and density bonuses near the new light-rail station.
Which Lynnwood neighborhoods do you build in most?
Our recent Lynnwood projects cluster in Alderwood Manor, Cedar Valley, Martha Lake, North Lynnwood, and South Lynnwood, Lake Serene. Each neighborhood has its own quirks — historic overlays, narrow lots, side-sewer age, ECA exposure — and our project list page for each one calls them out so you know what to expect before you call us.
ADU types we build in Lynnwood
Stand-alone backyard cottages built from the ground up — engineered for rental income, multi-generational living, or your home office.
Seamlessly integrated additions — basement, ground-floor, or wing conversions that maintain the architectural integrity of your existing home.
Convert an under-used garage into a high-end studio, office, or rental quarter without surrendering your driveway.
Structural expansions for growing families — second stories, primary suites, kitchen extensions. Steel, glass, and Pacific Northwest materials.
Full-service general contracting for remodels, renovations, and ground-up custom homes throughout the Puget Sound region.
Before you commit, we analyze zoning, lot coverage, setbacks, utilities, and ROI so you have a real number — not a guess.
Frequently asked, by service type
How big can a detached ADU (DADU) be in Seattle?
Under current Seattle SDCI rules, a DADU may be up to 1,000 sq ft of gross floor area on most single-family lots, with a maximum height of roughly 18–24 ft depending on roof form and lot size. We confirm the exact envelope against your zone (NR1/NR2/NR3) and lot coverage before design starts.
Go deeper: Read the DADU vs AADU in Puget Sound: which to build (2026) guide
Can I convert my Seattle basement into an attached ADU (AADU)?
In most cases, yes. The two hard requirements are code-compliant egress (a window or door per IRC R310) and minimum 7 ft ceiling height in habitable areas. We frequently underpin or saw-cut for an egress window-well and add a code-compliant exit during the conversion.
Can my detached garage be legally converted to a rental in Seattle?
Most can. SDCI treats a detached garage conversion as a DADU when it adds a kitchen and bath. The slab must meet frost-depth and moisture-barrier requirements (often retrofitted), and the structure typically needs new shear walls, a foundation upgrade, and full insulation per WSEC 2021.
Do I need a permit for a home addition in Seattle?
Yes — any addition that increases floor area, alters the building footprint, or modifies structural framing requires an SDCI building permit. Mechanical, plumbing, and electrical sub-permits run in parallel. We handle the entire SDCI submittal and inspection cycle in-house.
Are you a licensed general contractor in Washington State?
Yes. Golden State ADU Builders holds Washington L&I contractor license GOLDESA747LZ, carries general liability and workers' comp, and is bonded per RCW 18.27. We can provide a current Certificate of Insurance naming you as additional insured before contract.
What does a feasibility study actually include?
Zoning + setback analysis against the live SDCI / Bellevue / Kirkland code, a buildable-area diagram on your survey, utility capacity check (water, sewer, power), order-of-magnitude cost range, schedule range, and a rental-yield projection — delivered as a written report plus a 30-min review call.
Lynnwood ADU cost by build type
All-in pricing for a Lynnwood build, normalized to the local cost index (0.91× Seattle baseline). Click any service for a full Lynnwood-specific scope, deliverables, and contract.
| Build type | Typical sqft | Lynnwood all-in | Build time | Deep dive |
|---|---|---|---|---|
| DETACHED ADU in Lynnwood | 400–1,000 sqft | $127K–$364K | 6–8 months | Lynnwood cost data → |
| ATTACHED ADU in Lynnwood | 300–800 sqft | $86K–$291K | 4–5 months | Lynnwood cost data → |
| GARAGE CONV. in Lynnwood | 200–600 sqft | $59K–$218K | 3–4 months | Lynnwood cost data → |
| MODERN ADDITIONS in Lynnwood | Custom | $109K–$437K | Project dependent | Lynnwood cost data → |
| GENERAL CONTRACTING in Lynnwood | Any | Custom | Project dependent | Lynnwood cost data → |
| FEASIBILITY STUDIES in Lynnwood | — | $1,500 – $3,500 | 1–2 weeks | Lynnwood cost data → |
Need the math behind these numbers? See our Lynnwood ADU cost-per-sqft breakdown or the 2026 Puget Sound ADU cost report.
Lynnwood vs. nearby cities — at a glance
How Lynnwood compares to surrounding Puget Sound markets on permit window, minimum lot, and the 800 sqft DADU all-in price. Each row links to that city's full FAQ.
| City | Permit window | Min lot | 800 sqft DADU | Cost index |
|---|---|---|---|---|
| Lynnwood (this page) | 8–12 wk | 5,000 sqft | $420k–$525k | 0.91× |
| Mountlake Terrace ADU FAQ | 8–12 wk | 7,200 sqft | $425k–$530k | 0.92× |
| Edmonds ADU FAQ | 10–14 wk | 6,000 sqft | $455k–$565k | 0.98× |
| Shoreline ADU FAQ | 8–12 wk | 5,000 sqft | $440k–$545k | 0.95× |
| Mill Creek ADU FAQ | 10–14 wk | 7,200 sqft | $445k–$555k | 0.96× |
| Bothell ADU FAQ | 10–14 wk | 7,200 sqft (with 25% reduction for ADU lots) | $450k–$560k | 0.97× |
| Woodinville ADU FAQ | 10–14 wk | 8,400 sqft | $465k–$575k | 1.00× |
FAQs for nearby cities
Question we didn't answer?
Call (425) 642-4142 or send us your lot address — we'll come back with a feasibility read in 48 hours.
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