"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
4.8 STAR RATED40+ CUSTOMER REVIEWS
LICENSED · BONDED& FULLY INSURED
Seattle ADU & DADU Builder
MNBE designs, permits, and builds detached ADUs, attached ADUs, basement ADUs, and backyard cottages across Seattle, Bellevue, Kirkland, Redmond, and the Eastside, one team, one fixed price contract. King, Snohomish & Pierce County.
Fixed price contracts
Permits handled in house
Founder supervised
What We Build
Every ADU type Washington allows, built for your lot.
We are an ADU and DADU builder serving Seattle and the Eastside, from Bellevue and Kirkland to Redmond, Sammamish, and Mercer Island. If you can picture an extra home on your property we can build it, and we handle the entire process from the first sketch to the final inspection, so you never chase a permit or manage a subcontractor yourself.
An accessory dwelling unit can take four forms: a detached ADU (DADU) construction in Seattle, a freestanding backyard cottage set apart from your house; an attached ADU (AADU) joined to your home; a basement ADU conversion created from your lower level; or a garage conversion that reuses a structure you already have. Under Washington's HB 1337 rules you can add up to two units on most lots across Seattle and the Eastside, with no owner occupancy requirement and no added off street parking. We design, permit, and build all four, and after a free site visit we will tell you which one fits your lot, your budget, and your goals.
Schedule Free Estimate
4.8 STAR RATED40+ CUSTOMER REVIEWS
LICENSED · BONDED& FULLY INSURED
Seattle ADU Rules · 2026
The rules now work in your favor.
Washington's HB 1337 reshaped what you can build on a Seattle lot.
2
ADUs per lot
One attached plus one detached, on most residential lots.
1,200sq ft max
Max ADU size
Room for a real two bedroom home across Seattle and the Eastside.
No
Owner occupancy
Build it purely as a rental. The rule was removed in 2019.
0
Added parking
No mandatory off street space, so your yard stays open.
What does an ADU cost in Seattle?
Priced to your lot.
Every ADU is priced to your specific lot, never a generic per square foot number. Slope and soils, utility connections, access, and finish level move the total far more than floor area does, so we walk your property first. After a free site visit you get a written fixed price that covers design, permits, and construction, and the number we sign is the number we build to.
Every MNBE ADU includes
- Architectural drawings and design
- Structural engineering coordination
- Permits, plan check corrections, and inspections
- Full construction by our own licensed crew
- One fixed price contract, founder supervised
How It Works
From first site visit to keys, one team.
No handoffs and no surprises. Here is exactly how your ADU goes from idea to a finished, rentable space.
01
Free site visit
We walk your lot, confirm what your zoning and critical areas allow, and talk through your goals.
No cost
02
Design & feasibility
Architectural drawings, structural coordination, and a written bid, so you know the number before permits.
Fixed price
03
Permits
We prepare and submit to your city, answer every plan check correction ourselves, and schedule the inspections.
We handle it
04
Build
One licensed crew, founder supervised, from foundation to finishes, on the fixed price we signed.
Founder led
05
Keys
Final inspection, certificate of occupancy, and a finished ADU ready to live in or rent.
Move in ready
Reviews
What Seattle homeowners say about building with MNBE.
Verified five star reviews from owners who built their ADU, DADU, or renovation with us.
"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
Sammamish, WA · Whole home renovation
"We hired MNBE for a major exterior renovation: a 900 sq ft custom deck with metal railings, full exterior painting and new siding. From start to finish the experience was exceptional, responsive, meticulous and patient."
Santosh S.
Redmond, WA · Deck & exterior
Schedule Free Estimate
4.8 STAR RATED40+ CUSTOMER REVIEWS
LICENSED · BONDED& FULLY INSURED
FAQs · What Clients Ask Us
The ADU questions Seattle homeowners ask before they hire.
Real answers from a real builder. Call us if yours isn't here. We answer the phone Monday through Saturday.
Yes. Under Seattle's rules and Washington's HB 1337, you can build up to two ADUs on most residential lots, typically one attached and one detached, with no owner occupancy requirement and no added off street parking. That lets you pair a basement or above garage unit with a freestanding backyard cottage. We confirm exactly what your specific lot supports during the free site visit.
An ADU (accessory dwelling unit) is any independent living unit on your lot, with its own kitchen, bath, and entrance. A DADU is the detached version, a freestanding building that Seattle also calls a backyard cottage, while an attached ADU shares a wall or sits above the garage. The detached DADU is the most popular type for privacy and rental value.
It depends on your lot, and that is the honest answer. Slope and soils, utility connections, access, and finish level move the cost far more than floor area does, so we do not quote a generic per square foot number. After a free site visit you get a written fixed price that covers design, permits, and construction, and the number we sign is the number we build to.
A typical ADU runs several months from signed contract to certificate of occupancy, split across design, permitting at Seattle SDCI, and construction. A pre-approved DADU plan can shorten the permit step. We prepare the submittal, answer every correction ourselves, and hold the schedule we put in writing.
No owner occupancy is required in Seattle, that rule was removed in 2019, so you can rent the main house, the ADU, or both. A detached DADU is the strongest rental performer because it gives tenants a private entrance and address. We deliver a permitted, code compliant unit that is ready to lease once it passes final inspection.
We publish every question Seattle homeowners ask us about ADUs, permitting, and construction. Browse the full FAQ library for expert guidance.
View all FAQs
Contact Us · Free Estimate
Tell us about your ADU project.
We'll get back to you within one business day with a clear next step.
Contact information
Thank you for considering MNBE for your ADU or DADU project. We respond within one business day, Monday through Saturday.
(206) 637 0044
info@mnbe-wa.com
2014 Fairview Ave Unit 2308, Seattle, WA 98121