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DADU Builder
in Greater Seattle
We design and build detached ADUs (DADUs) that add private living space, rental income, and long-term value to your home — with a smooth, guided process from design to final inspection.
What We Build for Your Backyard
A DADU (Detached Accessory Dwelling Unit) is a standalone living space built in your backyard — perfect for rental income, multigenerational living, guest housing, or simply adding more space without moving. DADUs are private, flexible, and fully permitted as legal dwelling units.
We design and build DADUs that fit your lot, match your home’s architecture (or take on a modern look), and meet your city’s zoning and permit requirements. From feasibility and design to engineering, permitting, and construction, we handle the entire process.
Why Homeowners Choose DADUs
Rental income
Long-term rental income backed by strong local demand.
Private living space
A separate home that doesn’t change your main house.
Higher property value
A fully permitted, functional second home on your lot.
Flexible use
Family, guests, grandparents, adult children, office + living.
Types of DADUs We Build
Modern backyard cottage
Clean lines, large windows, and open floor plans.
Cottage-style DADU
Warm, homey designs that blend with the neighborhood.
Rental-ready DADU
Private layouts designed for long-term tenants.
Multigenerational home
Comfortable homes for family or future flexibility.
How Your Project Works
We handle every step for you, from the first site visit until you move in. A typical ADU or DADU takes about 6–12 months from design to move-in, depending mostly on permitting and size. You get a project-specific schedule after the feasibility review.
Feasibility review
We check zoning, setbacks, buildable area and utilities, and recommend the type of ADU that fits your lot and goals.
Design
Layout, materials and rooflines that match your home or take a more modern direction, with a line-item estimate.
Engineering & permits
Structural engineering and the full permit set for your city (SDCI in Seattle), including any utility upgrades.
Construction
Our crew builds the ADU, with regular updates and your approval on any change to scope or cost.
Final inspection & move-in
City inspections, a walkthrough together, and your new space is ready to rent or move in.
ADU, DADU or a Backyard Studio?
Three ways to add space to your property. Not sure which fits? We’ll recommend one after looking at your lot.
Backyard studio or office
- Our models from 120 to 200 sqft, or a custom size
- Work, hobby or guest space; no plumbing
- Often no building permit up to 200 sqft (Seattle is stricter)
- Built in about 3–5 weeks
Detached ADU (DADU)
- A standalone backyard home, up to ~1,000 sqft depending on the lot
- Kitchen, bathroom and bedroom: a legal dwelling unit
- Full design, engineering and permits
- About 6–12 months from design to move-in
Attached or conversion ADU
- Inside or attached to your home: addition, garage or basement
- A private entrance and its own kitchen and bathroom
- Full design, engineering and permits
- Can reuse an existing structure
What Affects the Cost
Every lot is different, so we price each project line by line. These are the main factors:
Get a line-item estimate for your property
We look at your lot, utilities and goals, then send a clear estimate with every cost listed, before design is final. No surprises later.
Request My EstimateSize & layout
Square footage, one or two stories, number of rooms.
Site & foundation
Slope, access for equipment, soil and foundation type.
Utility upgrades
Electrical capacity, sewer line and water service the city may require.
Finishes & fixtures
Kitchen, bathroom, flooring, windows and exterior materials.
Design, permits & fees
Architectural plans, engineering, permit and utility fees.
Why Build Your DADU With SDEK
Backyard building experience
From small studios to full backyard cottages, we know the design, zoning and utility questions that help a DADU fit your lot.
Designs that fit your lot
We maximize space, privacy and sunlight while staying within setbacks, height limits and lot coverage rules.
Full design–build delivery
One team handles feasibility, architectural plans, engineering, permitting and construction.
What Seattle Homeowners Say About Our ADU Builds
DADU FAQ
Rules differ by city. We check zoning, size limits, parking and utilities for your address in the feasibility review.
How big can a DADU be in Seattle?
Most Seattle DADUs can be up to around 1,000 sq ft depending on your lot size, zoning, and lot coverage. We verify exact limits during our feasibility review.
Do I need a separate utility hookup for a DADU?
Some DADUs require electrical or sewer upgrades depending on the capacity of your existing home. We coordinate all utility assessments and handle any upgrades required by Seattle Public Utilities or SDCI.
Will a DADU affect my backyard privacy?
Not if it’s designed the right way. We position windows, entries, and outdoor areas to maximize privacy for both your main home and the DADU — especially on smaller Seattle lots.
Can a DADU have two stories?
Yes, if your zoning and height limits allow it. Many Seattle homeowners choose a lofted or two-story DADU to maximize usable space on smaller lots.
Can I use my DADU as a short-term rental?
Seattle restricts short-term rentals in many cases. Most DADUs are best suited for long-term rentals (30+ days). We can walk you through the current rules so your DADU stays compliant.
How long does it take to build a DADU?
Most DADU projects take about 6–12 months from design to move-in, depending on the design, permitting, season and site conditions. We’ll give you a project-specific schedule after feasibility and design.
Can a DADU share a yard or outdoor space with my main home?
Yes. Many homeowners create small patios, shared spaces, or separate outdoor areas depending on how the DADU will be used. We help you plan a layout that works for privacy, access, and sunlight.
