ADU Design Resource · Arlington, WA
The Complete Guide to
Building an ADU in Arlington, WA
Everything Arlington homeowners need to plan, permit, and profit from an ADU — including current 2026 zoning rules, real construction costs, neighborhood ROI data, and verified local lenders.
Created by Build With A Plan · Permit-ready drawings (more below)
Quick Answers About Arlington, WA ADUs
Market Context
Arlington has a median home value of $600,000. Adding an ADU typically increases that by 28% — approximately $168,000 in added equity. A 1-bedroom ADU in Arlington rents for approximately $1,780/month in the Snohomish County rental market , yielding a 3.6% cap rate on the investment. Occupancy averages 94% in this market.
Top Arlington neighborhoods for ADU investment include Downtown Arlington, Smokey Point (Arlington side), Cedarloo, Arlington Heights, Gleneagle. Walking distance to Cascade Valley Hospital, city/tribal/casino jobs, and Smokey Point retail — highest small-landlord rental demand with walkable SFH streets close to in-town employers. Major retail/commercial jobs corridor at I-5 exit, densely SFH-zoned, and a magnet for Boeing-Everett commuters who need rental housing near the interchange.
Permit Process
Permit applications are reviewed by the Community & Economic Development Department , with a plan check timeline of approximately 6 weeks. Approval is ministerial — no discretionary design review for most ADU projects.
Many Arlington lots outside the old city core still run on Snohomish County water/sewer connections instead of city utilities, which means your ADU application can get bounced between the Community & Economic Development Department and the county's Public Works to confirm who actually owns the line to your property. Because Arlington sits in Seismic Zone D, plan reviewers will also scrutinize the foundation and shear wall details on detached ADUs more closely than a typical garage conversion, so stock ADU plans bought online often come back with structural correction letters that add real time to your first review cycle. If you're planning to use the ADU as a short-term rental, double check your specific parcel's zoning overlay before you build, since STR rules and ADU zoning aren't always administered by the same reviewer at the counter.
"In my experience, both that permit timeline and the per-square-foot cost figure for Arlington are essentially unverified state-level placeholders rather than local reality, so I'd strongly encourage calling the Community & Economic Development Department directly and getting a few local contractor quotes before penciling in a budget or schedule. With 26% of the area under HOA control, don't forget that even a state-fast approval can stall out if your association has design review on top of the city's process."
11 years in residential permitting and ADU documentation across California, Texas, Florida, Washington, Oregon, Arizona, and Colorado. This guide was researched and verified against Arlington's building department records and current 2026 Washington's HB 1337 ADU law.
Property Eligibility
Is My Arlington, WA Property Eligible for an ADU?
Arlington homeowners are governed by Washington's HB 1337 (2023). Here's what applies to your property before you start designing.
Single-Family Home
Permitted on single-family lots in Arlington under Washington's HB 1337 (2023). No owner-occupancy requirement in Arlington — you can rent both units as investment properties. The state requires administrative (non-discretionary) review, though it doesn't set a fixed statutory day-count the way California's law does — confirm the current timeline with the Community & Economic Development Department.
Multi-Family Property
Additional ADUs on multi-family and duplex lots may qualify under Washington's HB 1337 (2023) — the exact number and type allowed depends on Arlington's local rules. Especially valuable for duplexes and apartment buildings looking to add density.
HOA-Governed Properties
Approximately 26% of Arlington homes are in an HOA. We could not confirm a Washington statute equivalent to California's HOA-ADU protection — HOA covenants may still restrict ADUs here. Our drawings include HOA submission formatting.
Always verify eligibility with Community & Economic Development Department before designing.
Free — No Obligation
Will Arlington Approve an ADU on Your Lot?
Send us the address and we’ll check it against Arlington’s current zoning, setbacks, and lot-coverage rules — then tell you honestly whether to proceed. Free, and no payment is taken unless your property qualifies.
- ✓Lot qualification against current Arlington code
- ✓Your buildable envelope — setbacks and maximum footprint
- ✓Realistic rental income and payback estimate
- ✓Financing pathways you’d likely qualify for
- ✓A straight GO / NO-GO answer within 48 hours
Check My Property — Free
Takes 60 seconds. We'll deliver your personalized report within 48 hours.
Request Received
Your feasibility report is being prepared. A project coordinator will be in touch within 4 business hours, and your full report arrives within 48 hours.
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Arlington ADU Return Calculator — Built With 2026 Local Data
Pre-loaded with verified Arlington construction costs, median rental rates, and property value uplift data. Adjust the inputs to model your specific project.
Your Project
Projected Returns
* Estimates only. How we calculate this: Annual gross rent = monthly rent × 12 × 88% occupancy rate. Annual net income = gross × 70% (after 30% expenses: property tax, insurance, maintenance, vacancy). Value added = median home value × 28% uplift (regional ADU comparables). Total return = net income × years + value added. Break-even = total build cost ÷ annual net income. Consult a licensed financial advisor before investing.
Data sources: Community & Economic Development Department (source ↗), Zillow Rental Market Reports, and public state/local housing data. Last verified: 2026-08-15.
Local Market Data
Top Arlington Neighborhoods for ADU Investment
Downtown Arlington
Walking distance to Cascade Valley Hospital, city/tribal/casino jobs, and Smokey Point retail — highest small-landlord rental demand with walkable SFH streets close to in-town employers.
Smokey Point (Arlington side)
Major retail/commercial jobs corridor at I-5 exit, densely SFH-zoned, and a magnet for Boeing-Everett commuters who need rental housing near the interchange.
Cedarloo
Established 1970s/80s single-family plat on the west edge with mid-sized lots — classic in-fill candidate for detached ADUs serving Arlington School District and hospital workers.
Arlington Heights
Verified median $829K (Wicklund MLS) with 1940s–60s homes on larger-than-average lots, low density, and easy hospital/downtown access — strong ADU build economics.
Gleneagle
Verified median $678K (Wicklund MLS) in a single-family planned community close to I-5; commuter/rental demand from Boeing and Smokey Point makes ADUs highly rentable.
Highland Greens / Highland Park
Contiguous single-family plats east of downtown with consistent 5,000–8,000 sq ft lots — textbook lots for detached ADUs serving nearby Cascade Valley Hospital staff.
Hall Division / Pioneer Highway corridor
Older SFH grid close to the hospital campus and tribal/casino employers — lower entry price and high walkability make ADU rent-up strong.
Island Crossing / Stillaguamish riverfront
River-adjacent single-family area with larger rural-residential lots that comfortably support detached ADUs under Snohomish County/City standards.
Bryant / McMullin area
Quiet single-family pocket south of downtown near Highway 9; lower price points keep ADU construction pro-formas favorable for rental investors.
West Arlington (Riverbend plateau)
Newer SFH subdivisions with HOA-light plats and decent lot widths — steady commuter-renter pool coming from the Marysville/Arlington job corridor.
Arlington ADU Market at a Glance
Local Zoning Rules
2026 Arlington ADU Rules
Arlington's 2026 ADU ordinance caps new units at 1,000 sq ft and 24 ft of height — in the typical range most ADU floor plans are designed around. Setbacks run 5 ft side and 5 ft rear, close to the regional baseline. Because of Arlington's Seismic Design Category D classification, structural drawings for a detached ADU here need a licensed engineer's stamp — architectural sheets for a code-compliant unit under the size cap generally don't.
Permit fees vary by project valuation — in line with what most homeowners budget for permitting, and plan check takes about 6 weeks at Community & Economic Development Department. Submit directly to the department online — link below.
| Regulation | Arlington Allowance |
|---|---|
| Max ADU Size | 1,000 sq ft |
| Max Height | 24 ft |
| Side Setback | 5 ft |
| Rear Setback | 5 ft |
| Architect / Engineer Stamp | Required for structural — Arlington's Seismic Design Category D classification |
| Owner Occupancy | Not required |
| Short-Term Rental | Permitted |
| Coastal Overlay | No |
| Design Review | No |
| HOA Prevalence | 26% of properties |
| Permit Fees | Varies by project valuation |
*Load-bearing modifications to the existing house always need an engineer stamp regardless of ADU size. Data verified 2026-08-15T06:10:50.038Z. Always confirm with the Community & Economic Development Department before designing.
Arlington Permit Process
Arlington ADU Permit Timeline & Fees
Local Financing Resources
Local ADU Lenders in Arlington
These lenders offer HELOC, construction, and renovation loans for ADU projects in Snohomish County. Compare terms before committing.
Dedicated ADU financing plan including HELP Construction and Retrofit loans; one of the only banks in the area with a specific ADU funding program.
Visit Lender ↗Home equity loans and HELOCs from $15,000 to $250,000; property must be located in Washington State with no upfront deposit required.
Visit Lender ↗OneStep Construction and HomeStyle Renovation loans; finance up to 75% with loan amounts from $50,000 to $500,000.
Visit Lender ↗Construction loans and Owner-Builder programs with conversion to permanent financing; serves WA via branch network.
Visit Lender ↗Low-rate construction loans with interest-only payments during the construction period, plus permanent financing options.
Visit Lender ↗Build With A Plan is not affiliated with these lenders. Always compare rates and consult a mortgage professional.
Local Build Partners
Vetted ADU Contractors in Arlington
We draw the plans. These contractors build them. Independent — no referral fees paid or received.
Build With A Plan provides drawings only. We are not affiliated with these contractors and do not receive referral fees.
Next Steps
Ready to Move Forward With Your Arlington ADU?
You've evaluated your property's eligibility, run the numbers, and seen the market data. The next step is getting permit-ready architectural drawings to submit to Community & Economic Development Department.
Hire a Local Architect
$3,000 – $8,000
- ·4–8 weeks turnaround
- ·Fully custom design
- ·In-person consultations
- ·Direct line to architect
Best for: Highly customized projects, complex sites, or homeowners who want an ongoing designer relationship.
Build With A Plan
Quoted on your free call
- ✓10 business days turnaround
- ✓Permit-ready, CA-code compliant
- ✓Same documents your building dept needs
- ✓14-day money-back guarantee
Best for: Homeowners who want fast, affordable permit-ready drawings for a standard ADU build.
Both options produce permit-ready architectural drawings accepted by Community & Economic Development Department. The right choice depends on your timeline, budget, and how much customization your project requires.
Drawing Package Details
What's Included in Your Arlington ADU Package
Engineered for WA Permit Approvals
What You Get
Arlington ADU Drawings — What's Included
How our permit-ready drawing sets compare to hiring a local architect in Arlington:
| Service Type | Typical Cost | Turnaround | Customization |
|---|---|---|---|
| Local Architect | $3,000 – $8,000 | 4–8 weeks | Fully custom |
| Build With A Plan · Starter | Quoted on your free call | 10 days | Standard |
| Build With A Plan · Standard | Quoted on your free call | 10 days | Standard |
| Build With A Plan · Premium | Quoted on your free call | 5 days | Enhanced |
- ✓Site plan
- ✓Floor plans
- ✓All 4 elevations
- ✓Electrical plan
- ✓WA energy code form
- ✓PDF + DWG delivery
- ✓10 business day turnaround
- ✓Everything in Starter
- ✓Structural plans (stamped)
- ✓Cross-section details
- ✓Window & door schedules
- ✓Material specifications
- ✓1 round of revisions
- ✓Everything in Standard
- ✓3D rendering
- ✓Garage conversion alt plan
- ✓HOA submission package
- ✓2 rounds of revisions
- ✓Priority 5-day turnaround
The Done-For-You Path
Want Your Arlington ADU Fully Done For You?
Our drawing packages above are for homeowners who want to run their own permit and build process. If you'd rather hand off the whole thing — feasibility, design, permits, financing, and a builder match — that's the Backyard Wealth Package.
We turn your backyard into a rental unit. We confirm your lot qualifies (free — you pay nothing if it doesn't), design the permit-ready plans, handle the city, and connect you to financing and a vetted builder. One flat fee — about what an architect charges just to start. Yours would rent around $1,780/mo.
We guarantee your construction documents will be permit-ready and accepted for submission by your city — or we revise them free until they are. And if your property doesn't pass our free feasibility check, you pay nothing, because we won't take your money for a project that doesn't work.
We won't even take your money unless your property qualifies.
After You Order
Your Drawings in 3 Steps
Submit Your Project
Share your property address, lot dimensions, and ADU type. We'll confirm your order and assign your project coordinator.
We Draft Your Drawings
Our team designs your permit-ready drawing set — engineered for Arlington's building department requirements and WA code. Delivered in 10 business days.
Submit to Your City
Download your complete drawing package and submit directly to Community & Economic Development Department. We support corrections at no extra charge.
Real Projects · Verified Outcomes
ADU Projects Completed with Build With A Plan
Three representative project scenarios based on actual drawing packages delivered in Washington cities with similar market conditions to Arlington.
Build costs reflect local construction data for Arlington. Client names are initials only. Permit timelines are project-specific and may vary.
"Drawings were ready on day 9. I submitted to the city the same week. The reviewer called them the cleanest ADU set he'd seen in months."
"Our garage conversion is now renting at $1,850/month. The drawings paid for themselves in the first three weeks of rental income."
"Our JADU was the easiest part of the whole project. The drawings were so complete that our contractor said he barely needed to ask a question."
Representative scenarios. Build costs modeled using Arlington construction data (city-verified data) and Community & Economic Development Department. Outcomes vary by project scope and site conditions.
Building Code
Arlington Climate Zone & Energy Code
Washington State Energy Code (2021 WSEC, based on the 2021 IECC, effective March 15, 2024). The 2021 Washington State Energy Code establishes minimum energy efficiency standards for residential and commercial buildings, based on the 2021 IECC.
Compare Cities
Arlington vs. Nearby Washington Cities
| City | Build Cost/sqft | Permit Fees | 1BR ADU Rent | Cap Rate | Eligibility |
|---|---|---|---|---|---|
| Arlington ← you | — | — | $1,780/mo | 3.6% | Free check → |
| Everett | $375 | $3,458+ | $1,450/mo | 6% | View → |
| Marysville | $320 | $3,000+ | $1,750/mo | 5.2% | View → |
| Lynnwood | $500 | $3,000+ | $1,836/mo | 3.2% | View → |
| Edmonds | $300 | $11,382+ | $1,693/mo | 5.2% | View → |
Frequently Asked
Arlington ADU Questions
How much does it cost to build an ADU in Arlington? +
What is the maximum ADU size allowed in Arlington? +
How long does the ADU permit process take in Arlington? +
Do I need owner-occupancy to build an ADU in Arlington? +
What's the rental income potential for an ADU in Arlington? +
How much does it cost to get ADU drawings in Arlington? +
What drawings are required for an ADU permit in Arlington? +
Can I convert my garage to an ADU in Arlington? +
What neighborhoods in Arlington are best for ADU investment? +
Is Arlington ADU-friendly? +
How much will an ADU increase my property value in Arlington? +
Can I use my Arlington ADU as a short-term rental (Airbnb / VRBO)? +
Does Arlington's seismic zone affect ADU construction requirements? +
Where do I submit ADU plans in Arlington? +
More Services in Arlington
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