The permit guide, plain version

This guide does not restate City code. Rules for ADUs in Seattle changed several times between 2019 and 2023 and continue to change, so the source is always the SDCI ADU page. What follows is the order of questions, and what each one means for your lot.

1. Five questions about your lot

• How big is the lot, and how much of it is already covered? The parcel record has the size. Coverage includes the house, garage and decks.
• Is there an alley? It changes where a cottage can sit and how construction gets in.
• Which way does your sewer leave the house? The City's side sewer card for your address shows it. The run to a backyard unit is often the biggest cost surprise.
• Are there large trees? Protected trees can move the footprint.
• Is the lot sloped, or in a mapped critical area? Both add steps to the permit.

2. Pick the type that fits

A detached cottage needs yard and a path for utilities. An attached unit needs room beside or behind the house. A garage conversion needs a sound structure. A basement unit needs height, dry walls and a separate entry.

3. The permit stages

• Survey and site visit
• Design and a fixed construction price
• Submittal to the City
• Correction letters and resubmittal
• Permit issued, build, inspections
• Final inspection and keys

The City also publishes pre-approved backyard cottage plans, which can shorten review. Ask any builder whether they will build from them.

4. What drives cost

Sewer run, access, slope and soil, trees, size and finishes. Two identical plans can differ widely in price on two different lots. Ask for a fixed construction price in writing before the permit is filed, and for named allowances.

5. Questions to ask any builder

• Who answers the City's correction letters, and will I see them?
• Is the construction price fixed before you file? What is excluded?
• Is the schedule in the contract, by week?
• What is the workmanship warranty, and do you come back before the first year is out?
• Can I see your Washington contractor registration, bond and insurance?

6. On rental income

Many owners rent an ADU where the rules allow. Nobody can promise you a rent or a return; talk to an accountant and a local property manager before you count on it.

Questions? Setback Backyard Homes, (206) 555-0148.