Seattle homeowners are tapping into one of the smartest real estate investments available—building an Accessory Dwelling Unit (ADU) or Detached Accessory Dwelling Unit (DADU). Whether you're looking for rental income, multi-generational living, or increasing your property value, an ADU could be the best decision you make for your home.
But where do you start? Here’s everything you need to know about building an ADU in Seattle, including costs, zoning laws, and why it’s a game-changer for homeowners.
Why Seattle Homeowners Are Building ADUs
The demand for housing in Seattle is skyrocketing, and adding an ADU to your property makes financial and practical sense. Here’s why:
✅ Passive Income Potential – A well-designed backyard cottage or basement ADU can generate $1,500–$3,000+ per month in rental income.
✅ More Space for Family – Need a place for aging parents, grown kids, or a guest suite? A DADU offers independent living while keeping family close.
✅ Boost Your Property Value – Homes with high-quality ADUs sell for more, making this one of the best real estate investments in Seattle.
✅ Flexible Use – Use it as a home office, Airbnb rental, or even downsize into it later while renting out the main house.
ADU vs. DADU: What’s the Difference?
ADU (Attached Accessory Dwelling Unit): Built within or attached to the main house (think basement apartment or converted garage).
DADU (Detached Accessory Dwelling Unit): A separate structure in the backyard, also called a backyard cottage or laneway house.
Both offer unique advantages, but if you have space, a DADU gives you the most flexibility and privacy.
Seattle ADU & DADU Requirements: What You Need to Know
Seattle has embraced ADU-friendly zoning laws, making it easier than ever to build. Here are the key rules:
✔ Lot Size: No minimum size requirement—small city lots are eligible!
✔ Size Limits: ADUs can be up to 1,000 sq. ft.; DADUs can be up to 1,000 sq. ft. (or 1,200 sq. ft. on larger lots).
✔ Owner-Occupancy: Not required—you can rent out both your main home and ADU!
✔ Parking: No off-street parking required in most areas.
✔ Setbacks & Height: Must meet setback requirements (varies by lot size) and cannot exceed 24 feet in height.
How Much Does It Cost to Build an ADU in Seattle?
Cost depends on size, design, and finishes, but here’s a general breakdown:
💰 Garage Conversion ADU: $100K – $200K
💰 Basement ADU: $150K – $250K
💰 Detached ADU (DADU): $250K – $500K+
While the upfront cost may seem high, rental income can cover mortgage payments and even generate profit in a few years. Plus, it’s a long-term asset that appreciates in value.
The Process: How to Get Started
1️⃣ Design & Feasibility Study – Work with an experienced Seattle ADU builder to evaluate your lot, budget, and design options.
2️⃣ Permitting & Approvals – Seattle’s streamlined process makes this easier, but professional guidance ensures smooth approvals.
3️⃣ Construction & Build-Out – A quality contractor is key to avoiding delays and maximizing your ADU’s potential.
4️⃣ Rent, Move In, or Enjoy – Whether you rent it out, move in, or use it as a guest house, you now have a high-value investment!
Find the Right ADU Builder in Seattle
Building an ADU is a big investment, so choosing the right Seattle ADU contractor is crucial. Look for a team with:
✅ Experience in ADU & DADU construction
✅ Knowledge of Seattle zoning & permitting
✅ Transparent pricing & budgeting
✅ Strong portfolio of completed projects
Is an ADU or DADU Right for You?
If you’re sitting on underutilized space in Seattle, an ADU is a no-brainer. Whether you want to build wealth through rental income or create a custom living space for your family, now is the time to take advantage of Seattle’s ADU-friendly laws.
Ready to Build Your ADU in Seattle? Let’s Talk!
Looking for expert guidance on designing and building an ADU or DADU in Seattle? Contact us today for a free consultation! Let’s turn your property into a high-value investment.
