ADUs & Accessory Dwelling Units in Southwest Washington

Washington's 2023 statewide ADU law, HB 1337, requires cities and counties within urban growth areas — which includes Vancouver and the rest of Clark County's urban core — to allow accessory dwelling units on most residential lots under objective standards, and it limits how far local rules can go in restricting them, including most owner-occupancy requirements. The law was a significant shift toward more approvable, lower-friction ADU permitting statewide.

The City of Vancouver and the other jurisdictions we work in each layer their own local ADU standards on top of that state floor, so the exact envelope for your property depends on your specific city or county. We confirm the applicable rules during feasibility, then submit the plans, respond to plan-check comments, and pull the permit for your jurisdiction.

ADUs take several forms, and the right one depends on your lot, budget, and how you plan to use the space. A detached ADU (DADU) is a standalone backyard unit that offers the most privacy and flexibility. An attached ADU shares a wall with the main home and can be more efficient to build and connect to utilities. A garage conversion reuses an existing structure — often the fastest, lowest-cost path because the foundation, walls, and roof are already there.

We walk you through which type fits your parcel, your goals, and the rules that apply — and every option is built with the same rain-screen siding and moisture-managed envelope we use on the main house, since a Southwest Washington ADU has to survive the same wet climate.

State law establishes baseline size allowances and reduced setback requirements for ADUs, with a smaller footprint always permitted under the streamlined standards. Garage conversions and attached units follow rules tied to the existing structure. The exact maximum for your property comes down to lot size, unit type, and your city or county ordinance, which we verify before design so the plan we draw is the plan we can permit.

Utilities are a key part of the plan. Depending on the design and your existing service, we run dedicated or sub-metered electrical, water, sewer, and gas as needed — often new trenching and connections for a detached unit, or a tie-in to existing service for a garage conversion. Every ADU is designed to the Washington State Energy Code (WSEC), and we coordinate the inspections along the way.

Homeowners build ADUs for different reasons, and the layout follows the purpose. As a rental, an ADU can generate long-term income that helps offset a mortgage — and under HB 1337, jurisdictions generally cannot impose an owner-occupancy requirement on a standard ADU, which is part of what makes them work as rentals. As a family suite, an ADU keeps aging parents or adult children close with privacy on both sides. Many owners plan for both over time, so we design flexible units that can shift between uses.

If a connected expansion of the main house fits your goals better than a separate unit, compare an ADU with a home addition, or have us manage the whole build as your general contractor.