ADU Resources

The first step is understanding what’s possible on your property. Factors like lot size, zoning designation, setback requirements, existing structures, and utility access all determine whether an ADU is feasible; and what type and size would work best. Every lot is different, and a professional assessment early on can save significant time and money down the road. We can help you navigate these variables or point you to the City of Seattle’s interactive feasibility tools to get started on your own.

Building an ADU requires permits from your local jurisdiction, and the process can vary significantly depending on where you live. In Seattle, recent code changes have made ADU construction more accessible, but you’ll still need to navigate building permits, site plans, engineering reviews, and potentially environmental or utility approvals. The permitting timeline depends on the complexity of your project and how busy the jurisdiction is. Having experienced support through this process helps avoid costly delays and rejected applications.

ADU construction costs depend on size, complexity, site conditions, and finish level. A detached backyard cottage in the Seattle area can range from roughly $300,000 to $800,000 or more, depending on the scope. Costs include design, permitting, site preparation, utilities, construction through completion. Getting a realistic budget early; through a Rough Order of Magnitude estimate and pre-construction planning; helps you make informed design decisions before committing to construction.

There are several ways to finance an ADU project, including home equity loans, home equity lines of credit (HELOCs), construction loans, and cash-out refinancing. Some homeowners also explore local and state incentive programs designed to encourage ADU construction. The right option depends on your financial situation, timeline, and how you plan to use the unit. We recommend consulting with a lender experienced in ADU financing early in the process.

An ADU can generate meaningful return on investment through rental income, increased property value, or both. Many homeowners in the Seattle area see rental income that significantly offsets their construction costs over time. Beyond the financial return, ADUs also offer flexibility; housing for aging parents, adult children, or guests; and contribute to the growing demand for housing in our region. The long-term value depends on location, unit quality, and how the space is used.