Accessory dwelling units are one of the most popular ways to add value and flexibility to a Vancouver property. But an ADU is not a simple remodel — it is a small house project with all the same permits, trades, and coordination.
Types of ADUs in Vancouver, WA
| Type | Typical cost range | Best for |
|---|---|---|
| Garage conversion | $80k–$150k | Fastest path, existing envelope |
| Basement ADU | $70k–$140k | Separate entrance, no new foundation |
| Detached new build | $150k–$300k+ | Maximum privacy and rental income |
| Above-garage addition | $120k–$220k | Uses existing footprint, needs structural check |
Costs vary widely with site conditions, utility runs, and finish level. These ranges are realistic planning numbers, not quotes. A firm price comes after site visit, feasibility, and a full scope.
Typical ADU timeline
- Feasibility and zoning. Confirm setbacks, lot coverage, utility capacity, and allowed size.
- Design and selections. Floor plan, exterior look, fixtures, and finishes.
- Permits. Building, electrical, plumbing, and sometimes sewer or septic.
- Site prep. Foundation, utility trenching, or garage modification.
- Construction. Framing, mechanicals, insulation, drywall, finishes.
- Inspections and final. Rough, insulation, electrical, plumbing, final inspection.
Reality check: most ADU delays come from permitting, utility capacity, or homeowner selections made after the project starts. Lock the first two before design and the third before construction.
What to verify before you sign a contract
- Zoning and setbacks in writing from the city or county
- Electrical panel capacity and whether a service upgrade is needed
- Sewer/septic capacity and connection path
- Water meter and gas line routing
- Fire separation, egress, and ceiling height requirements
- Who pulls the permits and coordinates inspections
Financing and rental notes
ADUs can be financed through construction loans, HELOCs, or cash-out refinancing. Rental income potential depends on size, location, and local market. RestorationRepublic does not provide financial advice, but we can help size the project to a budget once financing is in place.
Frequently asked questions
What is an ADU?
An Accessory Dwelling Unit is a secondary, self-contained living space on the same lot as a single-family home. In Vancouver, WA this includes garage conversions, basement apartments, and detached backyard cottages.
How much does an ADU cost in Vancouver, WA?
A garage conversion typically starts around $80,000–$150,000. A detached new-build ADU can run $150,000–$300,000+ depending on size, utilities, foundation, and finishes. Site work, permits, and utility connections are often underestimated.
Do I need a permit to build an ADU in Vancouver?
Yes. ADUs require permits for the unit itself, plus separate permits for electrical, plumbing, and sometimes structural work. The City of Vancouver and Clark County both have ADU zoning rules, setbacks, and utility requirements that must be confirmed before design.
Can I convert my garage into an ADU?
Often yes, if the garage is structurally sound and meets setback, ceiling height, and egress requirements. Garage conversions are usually the fastest and most budget-friendly ADU path because the envelope already exists.
What are the biggest ADU mistakes?
Starting design before confirming zoning, assuming the existing electrical panel can handle the load, ignoring sewer/septic capacity, and choosing finishes before the budget is locked. These delays can add months and tens of thousands of dollars.
Keep reading
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