ADU and DADU Builders in Renton, WA
Renton allows two ADUs on a lot, each up to 1,000 square feet and 24 feet tall, attached to the house or detached.
- We check your parcel against Renton's shoreline and hazard maps first.
- We send the Permit Center a complete package the first time.
- You approve a written, itemized price before work starts.
By appointment. Limited start dates.
- Over 200 projects
- 4.9 on Google
- 20+ years of experience
- WA license VOLCABI792C6
What you can build on a Renton lot
Each is a complete second home with a kitchen, a bathroom and its own door, and each counts as one of the two units a Renton lot may hold.
Attached ADU
An addition on the side or back of the house, held to the same 1,000 square feet and 24 feet as any Renton ADU.
ADU inside the house
A basement or lower floor made into its own unit. In a house built before 1980, which is more than four in ten Renton homes, an asbestos survey comes before any wall is opened.
Detached ADU (DADU)
A backyard cottage built new, either to our drawings or from one of the eight base plans in the city's Permit Ready ADU program.
Garage conversion
An attached or detached garage turned into a unit, with insulation, windows, heat and plumbing brought in, inside the same size and height limits.
For the difference between an ADU and a DADU, see ADU Builders Across the Greater Seattle Area. Garage work that stays part of the house is on Garage Conversion, and the main house on home remodeling in Renton.
Renton ADU rules under RMC 4-2-110C
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The Renton rule
Two units, any mix
A legal lot with a house in Renton's residential zones can have two accessory dwelling units, attached, detached or one of each. Renton adopted these rules in June 2025 (Ordinance 6160) to meet the state ADU law, HB 1337.
What we doWe sketch the options your lot allows and price each before you choose.
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The Renton rule
1,000 square feet and 24 feet
Under RMC 4-2-110C an ADU may be up to 1,000 square feet and 24 feet tall. No off-street parking is required for one within a half mile walk of a major transit stop.
What we doWe measure your walking distance to transit early, because it decides whether a parking space goes on the plan.
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The Renton rule
Eight Permit Ready base plans
Through its Permit Ready ADU program the city offers eight pre-approved base plans, sized from 415 to 1,000 square feet. Owners who pick one work with city staff on a site plan and get an expedited review.
What we doWe build from a Permit Ready plan or draw a custom unit, and tell you which suits your lot.
Lots near Lake Washington, the Cedar River, May Creek, the Black River or Springbrook Creek fall under the Shoreline Master Program, and RMC 4-3-050 lists steep slope, landslide, seismic and coal mine hazards.
Renton ADU permits and timeline
City of Renton Permit Services handles ADU permits, and every submittal is electronic.
- Applying: the project name, address and scope go to the Permit Center by email, and a permit specialist replies with an upload link.
- Completeness: the city allows five days to confirm the application is complete.
- First review: residential decisions typically take two to three weeks, and revisions one to two weeks. Renton does not offer paid expediting.
- Trade permits: electrical, mechanical and plumbing permits are applied for online through the Civic Access Self-Service Portal and are typically issued the same day.
- On site: in or near residential areas, Renton limits a single family remodel or addition to 7 a.m. to 10 p.m. on weekdays and 9 a.m. to 10 p.m. on weekends; new construction runs 7 a.m. to 8 p.m. on weekdays and 9 a.m. to 8 p.m. on Saturdays, with no Sunday work (RMC 4-4-030.C.3).
How we build your Renton ADU
One licensed team, from the first site visit to the final inspection.
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Site visit and written price
We check the zoning, overlays, sewer and power, book an asbestos survey where the house needs one, and send a written, itemized estimate.
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Plans and permits
We prepare a Permit Ready or custom plan set and pull the building and trade permits Renton requires.
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Build and warranty
One project manager runs every trade and inspection, and the finished unit carries our 2-year workmanship warranty.
The team behind your ADU
A licensed general contractor, WA license VOLCABI792C6, a short drive from Renton.
Over 200 projects
Completed company wide, from single bathrooms to whole home remodels.
20+ years
Bar, who founded Volcano Builders, has been building for 20+ years.
132+ cities
Served across 8 counties in Western Washington.
4.9 on Google
Our rating on the main Volcano Builders Google Business Profile.
Browse Our Completed Remodeling Projects, and read the terms of our Remodeling Warranty for the Greater Seattle Area.
Finished kitchens and bathrooms from our crews
Every ADU needs a kitchen and a bathroom. These are finished rooms from other projects, labelled with what they are.
What homeowners say about working with us
Volcano builders did a phenomenal job on my bathroom remodel. They exceeded my expectations on many levels. Their designer helped me pick out all the tile and bathroom accessories to make sure everything matched in style. Communication was great and response time very fast whenever I had questions for them. They estimated the project would take 5-6 weeks but finished in 4 weeks! Excellent job! Loooooove my new bathroom! Including pics of the Before… and the After!
Gad an amazing experience with Volcano Builders on my kitchen project. Bar my project manager was friendly. He make sure to keep me updated during the whole project. Also is team is very nice.
Had a great experience working with Volcano Builders on remodeling bathroom and flooring in my condo! Bar and his team were very professional from estimates to timely completion of the job! Highly recommend!
Read more of our Google reviews, word for word, with video reviews from finished homes.
Our workmanship warranty
- 2 years standard. Our installation and labor are covered for 2 years from substantial completion.
- Up to 5 years. You can extend the workmanship coverage up to 5 years for an added charge, set in your contract.
- Not transferable. Coverage stays with the homeowner who signed the contract and does not pass to a new owner.
- Materials. Materials, finish materials included, carry the manufacturer's or supplier's warranty, and we help you file a claim.
Remodeling Warranty for the Greater Seattle Area
Related: Kitchen Remodeling Portfolio Across the Greater Seattle Area, Bathroom Remodeling Portfolio Across the Greater Seattle Area, ADU Builders Across the Greater Seattle Area, Home Remodeling Contractors in Renton, WA.
Renton ADU questions
How many ADUs fit on a lot in Renton?
Two, in any mix of attached and detached, on a legal lot with a house in a residential zone. Each can be up to 1,000 square feet and 24 feet tall under RMC 4-2-110C.
What is a Permit Ready ADU in Renton?
One of eight base plans the city has already approved, from 415 to 1,000 square feet. You choose a plan, work with city staff on the site plan and get an expedited review, which cuts the design stage short.
How long does Renton take to review an ADU permit?
The city allows five days to confirm the application is complete, and a first review decision on residential work typically takes two to three weeks. Revisions typically take one to two weeks, so a complete first package saves the most time.
Can I convert my garage into an ADU in Renton?
Often, yes. A converted garage counts as one of the two ADUs and must stay within 1,000 square feet and 24 feet. More on the work in Garage Conversion.
How do I get a price for a Renton ADU?
Book a consultation below. We visit the lot, talk through the unit and send a written, itemized price before any work starts. For background, read How Much Does It Cost to Build an ADU? and our Remodeling Pricing Guide.
Book your Renton ADU consultation
Four quick steps. Tell us about your project and we’ll reach out to discuss it and see if we’re the right fit.