Attached ADU
A self-contained unit built onto the side or back of your house.
Good at
- Shares a wall, so foundation and utility runs are shorter
- Easy to visit, still a separate front door
- Good for a parent who wants family close
What we check first
- How the new roof meets the old one
- Fire separation between the two units
- Matching siding and windows to the main house
Fits: Lots where the yard is tight but the house has room to grow sideways or back.
Plans that start here
The Parent SuiteStep-free entry, wide doors, a shower with no curb. Built for staying put.Detached600 sq ft1 bed, 1 bath$___k
Owner slot From-prices set by the builder. Example only; quoted after a site visit. What moves the price
Questions
Current rules: Seattle SDCI ADU page.
Is an attached ADU cheaper than a cottage?
Sometimes, because utility runs are short. Tying into an older house can add work you only find once walls are open, so we price that risk in writing before you sign.
Can we live in the house during construction?
Usually yes. We plan the weeks when water or power to the main house is off and tell you before the build starts.
Start with the lot.