Learning · ADU cost literacy
ADU cost factors
ADU scope depends on whether the unit is detached, attached, or a garage conversion, plus utility runs, fire separation, and the city standards that apply. Official Edmonds standards live in city code and handouts. This page does not publish a construction price.
What drives accessory dwelling unit cost in the North Sound — typology, utilities, and AHJ path. <strong class="text-white">Not a bid</strong>; official links only for fees/standards.
ADU cost drivers (illustrative — no prices)
What usually moves an ADU’s scope?
| Driver | Why it moves scope | Who to ask |
|---|---|---|
| Typology | A detached unit, an attached unit, a garage conversion, and an ADU inside a new residence are different scopes. | Ask the bidder which typology the proposal assumes, and confirm it against the city handout. |
| Foundation and utilities | Sewer, water, and power distance, plus any upsizing, change the site work. | Ask how far the new wet utilities run from the existing house. |
| Fire separation and egress | Attached or stacked units add fire separation, egress, and sound or privacy detailing. | Ask the bidder to name those items in the written scope. |
| Kitchen and bath wet cores | An ADU is a full dwelling mechanical, electrical, and plumbing package, not a guest-suite refresh. | Ask which wet rooms are in the scope. |
| Site constraints | Setbacks, trees, critical areas, parking, and alley or right-of-way access can change the footprint. | Confirm those limits with the city before the design is frozen. |
| City standards and permits | Edmonds standards live in the community development code and MyBuildingPermit ADU paths. Seattle fees live on SDCI pages. | Start at the Edmonds ADU hub and the official links there. This page does not republish a fee table. |
| How the unit will be used | Owner use and rental use can change the finish durability the owner asks for. | Say which use the allowance assumes. This page does not estimate a return. |
| Inspections on a tight lot | Inspection order and temporary occupancy are harder when the lot has little laydown room. | Ask the bidder for the inspection sequence in writing. |
Edmonds ADU hub · ADU readiness checklist · fees context: Seattle SDCI fees · MyBuildingPermit
ADU cost factors FAQ
Does the Board publish ADU construction prices?
No. ADU cost depends on detached vs conversion, utilities, foundation, fire separation, parking/access rules, and city standards. Official Edmonds standards live in city code and handouts — not Board fee tables.
Where do I find Edmonds ADU rules?
Start with the Board Edmonds ADU hub and official ECDC / MyBuildingPermit links there. Confirm live code before freezing design.
Are national ADU Cost vs Value numbers local bids?
No. Treat them as national study context only. Your parcel, utility runs, and AHJ fees control the real number.
Official resources
Outbound links to government portals only. The Board of Project Stewardship does not issue permits or licenses. Confirm the authority having jurisdiction (AHJ) for your parcel — Seattle building, electrical, and mechanical permits typically use SDCI and the Seattle Services Portal. Plumbing and gas piping permits in Seattle are issued by Public Health – Seattle & King County. Many other Puget Sound cities use MyBuildingPermit. Always re-verify contractors at WA L&I Verify before hiring.
Board feature
Another Story
Same home. Another story. Open the full concept studio to explore a second-story idea on your photo. Concept preview only, not a bid or permit document.