Lewis County, WA ADU (accessory dwelling unit) Rules (2026): City or County?
Lewis County ADU planning for Centralia, Chehalis, and unincorporated land: which office reviews the lot, and what Wolf checks on an I-5 delivery from Battle Ground.
Lewis County is an I-5 run north of Battle Ground: Woodland, Kelso, Castle Rock, then Centralia and Chehalis. Delivery is simpler than a mountain-pass route, but permitting splits three ways: City of Centralia, City of Chehalis, and unincorporated Lewis County each have their own counter.
Start with the Washington ADU laws guide for the state ADU rules inside urban growth areas, then confirm the local rules for your parcel. The usual surprises are floodplain, older side sewers, and a five-acre parcel with a city mailing address.
What to confirm before you pick a model
- Whether the parcel is inside Centralia, Chehalis, another city, or county land.
- If a second dwelling is allowed, and any minimum lot size or size cap the office is enforcing now.
- Sewer, septic, and water. Bedroom count changes septic math.
- Floodplain and access for a truck. A corridor lot can still have a ditch, a power drop, or a gate that stops the set.
- Parking and fire access the reviewer requires now, which may differ from an older FAQ.
City notes:
What Wolf does
We name the reviewing office, check whether a Battle Ground-built home can be set on that pad, and coordinate permit support with site work on Washington turn-key jobs, so you aren’t the one lining up the excavator with the factory schedule.
Request a free property evaluation.
General planning notes. Confirm current requirements with Lewis County or the city that covers the tax parcel.
Sources
Requirements change, so check the current forms and rules with your jurisdiction before you file. This is general information, not legal advice.