Main St ADU 550Sf Final Fp

Accessible one bedroom ADU

It’s time to add style, value, and flexible, poetic living opportunities right in your backyard.
Chosen by the City of Seattle for its landmark pre-approved DADU (detached accessory dwelling unit) design program, this small home design is a powerhouse of versatility, eye-catching design and pragmatic simplicity. At 600 sq. ft., this detached one-bedroom ADU incorporates Universal Design throughout and can be built as an accessible home.

Available with either a more traditional gable roof, or with a modern shed roof, it’s aesthetically flexible enough to work with varied neighborhood styles and architecturally designed for understated awesomeness.

Estimated Pricing

Basic Build (no upgrades): ~$139,000 (excludes excavation)
As-Built With Upgrades: ~$215,000 (excludes excavation)
Suggested Selling Price: ~$248,000 – $259,000 (subject to market)

Key seattle DADU features

Two available roof configurations, gable and shed.
Stairless entry (optional).
Energy-efficient insulation options available.
Customizable exterior finishes to match personal style.
Open-concept living areas for a spacious feel.
Sustainable building materials for eco-friendly construction.
Smart home technology integration for modern convenience.
Landscaping packages tailored to enhance curb appeal.

What’s Included in the Seattle DADU plan set?

If you’re a resident of Seattle, the Seattle DADU plan set includes almost everything the City requires to get your permit, and you’re on the fast track to building your new backyard home.
As part of the City of Seattle’s pre-approved DADU program, the Seattle DADU plan set includes engineering and energy calculations specific to Seattle’s Municipal Code.

In order to obtain a permit in Seattle, you will still need a site plan specific to your property as well as the completed permitting paperwork. Please contact us to discuss completing your plan set for a Seattle permit.

Exclusions

Under United Signature / Signature Build, site preparation, utilities, foundation work, and any required drainage, hardscape, fire suppression, or flame-retardant systems are not included in the base package price. These items, along with applicable sales tax, will be evaluated and itemized separately in your detailed cost breakdown after our team reviews the specific conditions and requirements of your property. Any visual renderings or illustrations may show optional features or upgrades that are not part of the standard package offering. For complete and accurate information on what is included, please refer to the written specifications and scope of work provided for your project.

Main St ADU 550Sf Final Fp

Package details

Heading #3	Heading #3
Project type	Compact
Size	Tiny ADU (483 sq ft)
No. of rooms	1
No. of baths	0.75 BA
ADU type	Luxury
Notable	Furnished
Location (state)	Washington

Structure

From the mudsill up, this ADU includes a complete, code-compliant structural shell: engineered floor and roof systems, all interior and exterior framing, required structural hardware, and full OSB wall sheathing installed to current building standards.

Architectural

Included in the quote to support permitting and construction requirements. Final plans and engineering scope may vary based on site conditions, jurisdiction, and project-specific needs.

Siding & Trim

Hardie 7-1/4″ smooth lap siding with 5/4″ x 4″ trim at openings and open soffits.

Roofing

Black asphalt shingle roof installation (per selection) with 15-year warranty.

Windows

Prime Windows – Series 9000.

Exterior Door

6’8″ insulated fiberglass exterior door with partial glass, prepped for handle + deadbolt (black factory-finished).

Plumbing

PEX supply and ABS drain rough-in, plus one exterior cold-water hose bib located outside the bathroom.

HVAC

One (1) mini-split system serving two (2) zones, kitchen and bathroom exhaust ventilation, and one (1) in-wall electric heater in the bathroom.

Electrical

125A or 200A service (as available from the main home), standard wiring/outlets, and code-required AFCI/GFCI protection.

Lighting

Eight (8) recessed lights, two (2) wall-mounted fixtures, and three (3) ceiling-mounted fixtures.

Insulation

Fiberglass insulation meeting the current Washington State Energy Code (2025). Optional upgrade: AeroSeal (if requested).

Drywall

Code-compliant drywall installation with light-to-medium orange peel texture and square corner bead throughout.

Interior Millwork & Doors

Hollow-core 1- or 2-panel interior doors with standard casing, base, and window sills.

Cabinetry, Countertops & Vertical Tilework

Craftsman-style cabinetry with color selection from United Signature showroom samples.

Bath Accessories & Kitchen Appliances

Kingmore Plumbing builder selections (Marcato line for faucets), standard single-control shower system, and appliances per United Signature design package.

Floor Coverings

LVP throughout (showroom selection). If applicable: main level/stairs LVP and second-floor carpet.

Paint

Up to three (3) exterior colors, one (1) neutral interior wall/ceiling color, and white millwork + interior doors.

Closets

Wire shelving: four (4) rows in pantry, one (1) row in closet, and one (1) shelf above washer/dryer.

Final Earthwork & Clean Up

Final grading and cleanup to meet code within five (5) feet of the foundation perimeter.

How DADU will look like

Heading #3	Heading #3
Project type	Family
Size	Spacious 1,216 sq ft
No. of rooms	2
No. of baths	2.25 BA
ADU type	Modern/Luxury
Notable	Modern Build
Location (state)	Seattle, WA

Heading #3	Heading #3
Project type	Family
Size	Spacious ADU (1,143 sq ft)
No. of rooms	2
No. of baths	2.25 BA
ADU type	Modern
Notable	Furnished
Location (state)	Washington

Heading #3	Heading #3
Project type	Spacious
Size	Large ADU (1,213 sq ft)
No. of rooms	2
No. of baths	2.25 BA
ADU type	Luxury
Notable	Furnished
Location (state)	Washington

Heading #3	Heading #3
Project type	Family
Size	Standard ADU (800 sq ft)
No. of rooms	2
No. of baths	1 BA
ADU type	Modern
Notable	Furnished
Location (state)	Washington

Heading #3	Heading #3
Project type	Family
Size	Large ADU (700 sq ft)
No. of rooms	2
No. of baths	1 BA
ADU type	Luxury
Notable	Furnished
Location (state)	Washington

Heading #3	Heading #3
Project type	Family
Size	Large ADU (994 sq ft)
No. of rooms	2
No. of baths	0.75 BA + 2 Car Garage
ADU type	Contemporary
Notable	Furnished
Location (state)	Washington

What people say about us

United Signature handled a large and complex kitchen reconstruction and remodel after a leak was discovered in the wall and under the floorboards. They were great communicators and helped me handle insurance and the HOA.

We had a bathroom and kitchen remodel done by Oleg (senior project manager), Natasha (lead designer) and Sergei (project manager). Excellent, high quality work. Always available and professional.

Exceptional service! I recently had my kitchen renovated by United Signature Design and Build and I couldn’t be happier with the results. From the initial consultation to the final details, everything went so smooth.

Oleg, Anna, and their team made all of our kitchen dreams come true! This review is long overdue but they were the absolute best team to work with. We will absolutely be using their services again when we decide to renovate our master bathroom!

It was a pleasure to work with United Signatu. Company perform best quality of services and products. Friendly approach, time efficiency. If you are looking for a project well done I strongly recommend United Signature .

Awesome kitchen remodeler company. Got the job done quick and on time. Will definitely use them again when I have remodel needs. I recommend to everyone looking for a good kitchen remodeler. Also shoutout to Nina for doing a great job with her work.

Compact

Main St ADU 550Sf Final Fp

Accessible one bedroom ADU

Estimated Pricing

Key seattle DADU features

What’s Included in the Seattle DADU plan set?

Exclusions

Main St ADU 550Sf Final Fp

Package details

How DADU will look like

Let us help you to choose the best package according to your requirements.

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What people say about us

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