ADU Design Resource · Des Moines, WA
The Complete Guide to
Building an ADU in Des Moines, WA
Everything Des Moines 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 Des Moines, WA ADUs
Market Context
Des Moines has a median home value of $560,000. Adding an ADU typically increases that by 25% — approximately $140,000 in added equity. A 1-bedroom ADU in Des Moines rents for approximately $1,668/month in the King County rental market , yielding a 5.5% cap rate on the investment. Occupancy averages 93% in this market.
Top Des Moines neighborhoods for ADU investment include Highline College Area, Marina District, Central Des Moines, Pacific Ridge, North Hill. Extreme rental demand driven by the large student population of Highline College. High demand due to proximity to downtown jobs, waterfront attractions, and commercial hubs.
Permit Process
Permit applications are reviewed by the Building Division , with a plan check timeline of approximately 10 weeks. Permit fees in Des Moines range from $9,000 to $28,000 depending on project scope. Design review: Yes - critical area review (and historic district review if applicable)
Des Moines properties within the Coastal Overlay Zone require a Coastal Development Permit (CDP) in addition to standard building permits. CDPs add 2–6 months to the permit timeline and require compliance with both local ordinances and applicable state coastal zone management standards.
Homes near the bluffs or shoreline in Des Moines often fall inside the state's coastal overlay zone, which means you'll need a separate Shoreline Substantial Development Permit on top of your regular building permit — this can tack on 6-8 extra weeks and requires a habitat/environmental review before the Building Division will even look at your plans. Because the city sits in Seismic Zone D, engineers also tend to require deeper footings or additional shear wall bracing than you'd see in a typical Puget Sound suburb, which can push your structural plan check costs up unexpectedly. On top of that, older neighborhoods like Woodmont and Redondo frequently have undersized side sewer lines from the 1960s, so King County may require a sewer capacity check before signing off on your final utility connection.
"In my experience, that 10-week timeline and per-sqft cost figure are Des Moines state-level estimates rather than locally verified numbers, so I'd call the Building Division directly and get a couple of local contractor quotes before penciling in a budget or start date — and don't overlook that coastal overlay, because the CDP review adds real time on top of standard plan check that a lot of homeowners don't anticipate."
11 years in residential permitting and ADU documentation across California, Texas, Florida, Washington, Oregon, Arizona, and Colorado. This guide was researched and verified against Des Moines's building department records and current 2026 Washington's HB 1337 ADU law.
Property Eligibility
Is My Des Moines, WA Property Eligible for an ADU?
Des Moines 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 Des Moines under Washington's HB 1337 (2023). No owner-occupancy requirement in Des Moines — 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 Building Division.
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 Des Moines's local rules. Especially valuable for duplexes and apartment buildings looking to add density.
HOA-Governed Properties
Approximately 26% of Des Moines 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.
Coastal Zone Properties
Properties within Des Moines's Coastal Overlay Zone require a Coastal Development Permit (CDP) in addition to standard building permits. This adds 2–6 months to the timeline. Our drawings flag coastal requirements and meet both local and applicable state coastal zone management standards.
Historic Districts
Yes - critical area review (and historic district review if applicable)
Always verify eligibility with Building Division before designing.
Free — No Obligation
Will Des Moines Approve an ADU on Your Lot?
Send us the address and we’ll check it against Des Moines’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 Des Moines 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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Des Moines ADU Return Calculator — Built With 2026 Local Data
Pre-loaded with verified Des Moines 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 × 25% 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: Building Division (source ↗), Zillow Rental Market Reports, and public state/local housing data. Last verified: 2026-08-15.
Local Market Data
Top Des Moines Neighborhoods for ADU Investment
Highline College Area
Extreme rental demand driven by the large student population of Highline College.
Marina District
High demand due to proximity to downtown jobs, waterfront attractions, and commercial hubs.
Central Des Moines
Dense concentration of single-family homes with high central accessibility.
Pacific Ridge
Larger lot sizes and lower entry costs make it ideal for detached ADU development.
North Hill
Strong residential SFH density providing numerous opportunities for ADU conversion.
South Des Moines
Strong rental demand from employees of the nearby Sea-Tac International Airport.
Woodmont
Spacious lots that easily accommodate large, detached luxury ADUs.
Zenith
Established residential area with high SFH density and stable demand.
Redondo
High property values but strong potential for high-end short-term vacation rentals.
Huntington Park
Quiet suburban lot characteristics suitable for residential ADU expansion.
Des Moines ADU Market at a Glance
Local Zoning Rules
2026 Des Moines ADU Rules
Des Moines's 2026 ADU ordinance caps new units at 1,200 sq ft and 24 ft of height — in the typical range most ADU floor plans are designed around. Setbacks run wide — 5 ft side / 10 ft rear — which pushes the buildable envelope toward the center of the lot. Because of Des Moines'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 run $9,000–$28,000 — among the higher permit costs we track, and plan check takes about 10 weeks at Building Division. Submit directly to the department online — link below.
| Regulation | Des Moines Allowance |
|---|---|
| Max ADU Size | 1,200 sq ft |
| Max Height | 24 ft |
| Side Setback | 5 ft |
| Rear Setback | 10 ft |
| Architect / Engineer Stamp | Required for structural — Des Moines's Seismic Design Category D classification |
| Owner Occupancy | Not required |
| Short-Term Rental | Permitted |
| Coastal Overlay | Yes — CDP may be required |
| Design Review | Yes - critical area review (and historic district review if applicable) |
| HOA Prevalence | 26% of properties |
| Permit Fees | $9,000–$28,000 |
*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 Building Division before designing.
Des Moines Permit Process
Des Moines ADU Permit Timeline & Fees
Local Financing Resources
Local ADU Lenders in Des Moines
These lenders offer HELOC, construction, and renovation loans for ADU projects in King County. Compare terms before committing.
Washington's largest credit union; nearest branch 25250 Pacific Hwy S (Redondo/Kent, ~2 mi from Des Moines 98198); HELOC intro rate as low as 4.49% APR for 6 months, also offers construction and home-improvement loans.
Visit Lender ↗Serves South King County with nearby branches in Federal Way, Kent, Burien, and Tukwila; offers two-time-close construction loans usable for major renovations and ADUs; HELOC intro of 4.99% APR for 6 months also available.
Visit Lender ↗Has a branch inside Des Moines WA at 21401 International Blvd (98198); offers construction-to-permanent loans and HELOCs (Washington HELOC APR around 6.375%), suitable for ADU projects.
Visit Lender ↗Washington-state savings bank with a dedicated ADU financing program offering six loan options designed for ADU builds ($150k–$250k typical cost); also offers HELOC (6.875% variable APR, up to $400k) and construction loans.
Visit Lender ↗Specialty ADU/renovation fintech that partners with credit unions nationwide (including Washington) to offer ARV-based renovation loans — borrowers get up to 11x more borrowing power on average vs. standard HELOCs without refinancing the first mortgage.
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 Des Moines
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 Des Moines 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 Building Division.
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 Building Division. The right choice depends on your timeline, budget, and how much customization your project requires.
Drawing Package Details
What's Included in Your Des Moines ADU Package
Engineered for WA Permit Approvals
What You Get
Des Moines ADU Drawings — What's Included
How our permit-ready drawing sets compare to hiring a local architect in Des Moines:
| 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
- ✓Coastal Zone supplement
- ✓2 rounds of revisions
- ✓Priority 5-day turnaround
The Done-For-You Path
Want Your Des Moines 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 $1,668/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 Des Moines'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 Building Division. 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 Des Moines.
Build costs reflect local construction data for Des Moines. Client names are initials only. Permit timelines are project-specific and may vary.
"We'd been quoted $6,200 by a local firm for the same permit-ready set. Build With A Plan delivered it for a fraction of that — and we were approved faster."
"Conversion permit came back approved on the first review. The drawings handled every detail — egress, HVAC, electrical. Nothing was missing."
"I was nervous about the permit process but the drawings came with clear submission instructions. Approved without a single correction cycle."
Representative scenarios. Build costs modeled using Des Moines construction data (city-verified data) and Building Division. Outcomes vary by project scope and site conditions.
Building Code
Des Moines Climate Zone & Energy Code
Washington State Energy Code (WSEC) — Des Moines, WA is not a California city, so Title 24 does not apply. The applicable code is the 2021 Washington State Energy Code (WSEC), based on the 2021 IECC and adopted as WAC 51-11R (residential) and WAC 51-11C (commercial), effective statewide March 15, 2024, with Washington-specific amendments that exceed base IECC requirements to advance statewide decarbonization.
Compare Cities
Des Moines vs. Nearby Washington Cities
Frequently Asked
Des Moines ADU Questions
How much does it cost to build an ADU in Des Moines? +
What is the maximum ADU size allowed in Des Moines? +
How long does the ADU permit process take in Des Moines? +
Do I need owner-occupancy to build an ADU in Des Moines? +
What's the rental income potential for an ADU in Des Moines? +
How much does it cost to get ADU drawings in Des Moines? +
What drawings are required for an ADU permit in Des Moines? +
Can I convert my garage to an ADU in Des Moines? +
Does Des Moines have a coastal overlay for ADUs? +
What neighborhoods in Des Moines are best for ADU investment? +
Is Des Moines ADU-friendly? +
How much will an ADU increase my property value in Des Moines? +
Can I use my Des Moines ADU as a short-term rental (Airbnb / VRBO)? +
Does Des Moines's seismic zone affect ADU construction requirements? +
Where do I submit ADU plans in Des Moines? +
More Services in Des Moines
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