MDK Permitting › Permit guides
What permits does an ADU or garage conversion need?
A building permit plus electrical, plumbing and mechanical permits, and usually system development charges. Here's the full picture.
Which permits will I need?
An ADU or garage-to-living-space conversion usually needs a building permit plus electrical, plumbing and mechanical permits. We handle all of them as one job.
What are system development charges?
SDCs are one-time fees cities charge new homes and ADUs for parks, sewer, water and roads. They can add thousands and vary a lot by city. Some cities waive or reduce them for ADUs. We look them up for your lot.
Does it need an engineer?
Usually, yes. We draw the engineered plans and a licensed Oregon professional engineer stamps them, about $200 at cost.
What do you need from me?
Your address, rough size, what's there now, and photos. We measure and draw the rest.
What it costs
Our price, plus city permit fees worked out from each city’s published fee schedule. City fees are paid to the city and the final amount is set at review. Construction isn’t included.
| Example | MDK price | Washington County | Hillsboro | Portland | Clackamas County | Marion County |
|---|---|---|---|---|---|---|
| 750 sq ft backyard ADU Building permit, Electrical permit, Plumbing permit, Mechanical permit | $3,100 plans, engineering & permits + engineer stamp about $200 | About $5,615 | About $1,835 | From $3,150 | About $2,730 | About $2,010 |
| 400 sq ft garage conversion Building permit, Electrical permit, Plumbing permit, Mechanical permit | $2,625 plans, engineering & permits + engineer stamp about $200 | About $3,940 | About $1,435 | From $2,400 | About $2,295 | About $1,510 |
County columns are for areas outside city limits. Other cities have their own fees. Get your exact numbers with the price builder.
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Pick your project, answer a few questions, and get a free proposal by email. Or just call. Calls are always free.
More permit guides: Decks · Retaining walls · Outdoor stairs · Porch & patio covers · Additions · Panels, EV chargers & hot tubs · Load-bearing walls · Sheds & fences
General guidance for Oregon homeowners. Rules vary by city and county, and the building official makes the final call. Prices checked against published fee schedules in November 2026.