What is an ADU?
An accessory dwelling unit (ADU) is a complete, independent living space on the same lot as a primary home. It typically has its own entrance, kitchen, bathroom and sleeping area. Homeowners build ADUs for aging parents, adult children, guests, a home office or potential rental income.
Washington State has expanded ADU options in recent years, and many cities — including those in King County — have updated their codes. Because rules continue to change, it is important to check the current City of Kent requirements for your specific property early in the process.
Common types of ADUs
Detached ADU
A new, standalone structure in the backyard. Detached units offer the most privacy and design flexibility but involve a full building scope: site work, foundation, framing, utilities and finishes.
Garage conversion
Converting an existing garage into living space can reuse part of the structure. It still requires upgrades — insulation, windows, plumbing, electrical, and often floor and foundation work — to meet code for a dwelling.
Attached ADU
An addition connected to the main house with its own entrance. Attached units share a wall with the home, which can simplify some utility connections. Room additions follow a similar construction process.
Interior conversion
Some homes have a basement or lower level that can become a separate unit where allowed, with appropriate egress, separation and systems.
Questions to answer before you design
- How will the space be used? Family, guests, rental or work space all affect the layout and finishes.
- Where can it go on the lot? Setbacks, easements, trees, slopes and access all matter.
- How will utilities connect? Water, sewer, power and drainage requirements affect cost and design.
- What size makes sense? Local rules set limits, and your budget and lot will narrow the options further.
- Is parking or access required? Requirements vary by jurisdiction and location.
Answering these early helps avoid redesigns later and gives you a realistic picture of what is possible.
How permitting and construction typically work
Most ADU projects follow a similar path: feasibility review, design, permit submittal, plan review and revisions, then construction with inspections at key stages. Our permit and inspection coordination keeps that process organized so you are not managing it alone.
During construction, the work generally moves from site preparation and foundation to framing, roofing and exterior, rough-in of plumbing, electrical and mechanical systems, insulation and drywall, and finally interior finishes and a final inspection.
Why one team helps
ADUs combine design, permitting and a full construction scope. Working with one company that coordinates all of it means fewer handoffs and a single point of contact from the first conversation to the final walkthrough. Learn more about our ADU construction services.
Frequently asked questions
Do I need an architect to build an ADU?
Most ADUs require permit-ready plans prepared by a qualified designer or architect, and some need engineering. We coordinate with the design team as part of the project.
Can I convert my garage into an ADU?
Often, yes, depending on the structure, zoning and code requirements. A garage conversion still needs upgrades for insulation, egress, plumbing and electrical.
Where can I check Kent ADU rules?
The City of Kent planning and permitting departments publish current ADU requirements. We also review them with you during planning.
