"We hired MNBE to build our ADU in Bellevue, and the entire experience was amazing. They handled everything from foundations and framing to kitchen, siding, windows and HVAC."
Zena Heywood
Bellevue, WA · Attached ADU
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How many ADUs can I build on my lot?
Two on most residential lots in Washington's urban areas: two attached, one of each, or two detached. Answered by MNBE founder Aharon Ben Elisha. Checked October 28, 2026.
RCW 36.70A.681(1)(c) 2 ADUs per lot Any mix of attached and detached
The Short Answer
Two, in any mix.
Two. Washington requires cities to allow at least two ADUs on lots inside an urban growth area that allow a single-family home: two attached, one attached and one detached, or two detached, in one or two buildings.
Seattle, Bellevue, Kirkland and Redmond all allow two. The exceptions are narrow: lots with critical areas or their buffers, lots without public sewer, and a few local overlay and shoreline areas, such as parts of Kirkland, that allow fewer.
On most lots the real limit is what fits: each city's size cap, floor area, lot coverage, setbacks and trees. In Seattle and Redmond, ADUs also count toward the lot's unit limit.
Seattle · Bellevue · Kirkland · Redmond
ADUs per lot, city by city.
Each city's full rules, with the code section behind every number: Seattle, Bellevue, Kirkland and Redmond.
2
Seattle
1,000 sq ft each, 1,200 with three or more bedrooms.
2
Bellevue
1,200 sq ft each.
2
Kirkland
1,200 sq ft each.
2
Redmond
1,000 sq ft each.
City by City
What the law says, city by city.
State law sets the floor. Each city's code adds its size cap and limits.
| Where | ADUs per lot and size cap | Source |
|---|---|---|
| Washington State | At least two ADUs on lots that allow a single-family home inside an urban growth area, attached, detached or one of each. Cities can't cap ADU size below 1,000 sq ft. | RCW 36.70A.681(1)(c), (f) |
| Exceptions | Lots with critical areas or their buffers, and lots without public sewer, can be treated differently. | RCW 36.70A.680, .681 |
| Seattle | Two ADUs, attached, detached or stacked, in any mix. 1,000 sq ft each, or 1,200 with three or more bedrooms. | SMC 23.42.022 |
| Bellevue | Up to two ADUs per lot, in any combination. 1,200 sq ft each. | LUC 20.20.120 |
| Kirkland | One attached and one detached, or two of either type. 1,200 sq ft each. Lots in the Residential-L shoreline environment are limited to one. | KZC 115.07 |
| Redmond | Two ADUs or tiny homes per residential lot. ADUs 1,000 sq ft each, tiny homes 400 sq ft. | RZC 21.04.1110 |
Checked October 28, 2026. A plain-English summary, not legal advice. The code governs, and we confirm it for your lot.
Reviews
What Seattle homeowners say about building with MNBE.
Verified five star reviews from owners we guided through ADU feasibility, permitting, and construction.
"We hired MNBE for a full renovation of our 100 year old home and the results exceeded expectations, structural upgrades, new insulation, a luxury bathroom, a high end kitchen, a new roof and mini split AC."
Dave Gierok
Redmond, WA · DADU
"My mom hired MNBE Construction for her two-bedroom DADU in Seattle, and watching the process up close was impressive. They did it all: design, architectural plans, the building permit, and the full construction. … The communication was excellent and there were never any surprises."
Maryam Z.
White Center, WA · ADU
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FAQs · Related questions
Questions about building two ADUs.
More answers: Can an ADU be two stories? · Can an ADU have its own address? · Do you have to live on the property?. City rules: Seattle, Bellevue, Kirkland and Redmond.
Yes. State law requires cities to allow two detached ADUs, in one building or two, and Seattle, Bellevue, Kirkland and Redmond allow it.
Yes, for long-term rentals. State law bars owner-occupancy requirements, so all three units can be rented.
Not in Seattle, Kirkland or Redmond, which require no ADU parking. Bellevue requires none for an ADU under 1,000 sq ft or near a major transit stop, and one space otherwise. State law bars ADU parking within half a mile walking distance of a major transit stop.
Space. Floor area limits, lot coverage, setbacks and trees decide what fits. We test both units against your lot during the free site visit.
Contact Us · Free Estimate
Tell us about your project.
We'll check your address against your city's ADU code and get back to you within one business day with a clear next step.
Contact information
Thank you for considering MNBE. Thank you for considering MNBE. Tell us your address and we will tell you, in writing, what your city's code allows on your lot. We respond within one business day, Monday through Saturday.
(206) 637 0044
info@mnbe-wa.com
2014 Fairview Ave Unit 2308, Seattle, WA 98121