MDK Permitting › Permit guides
What permits does a home addition need?
A building permit, usually an electrical permit, and plumbing or mechanical permits if you're adding a bathroom or heat.
Which permits will I need?
Any addition that adds floor area needs a building permit. Most also need an electrical permit for new circuits, plus plumbing if you add a bathroom and mechanical if you extend ducts or add a heat pump.
Does it need an engineer?
Usually, yes, for the foundation, beams and how it ties into the house. We draw the engineered plans and a licensed Oregon professional engineer stamps them.
How long does it take?
It depends on the city and how busy they are. Additions take longer than small permits because more reviewers look at them. We answer every correction the city sends so it keeps moving.
What do you need from me?
Your address, rough size, what goes in it, 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 |
|---|---|---|---|---|---|---|
| 350 sq ft room addition Building permit, Electrical permit, Mechanical permit | $2,250 plans, engineering & permits + engineer stamp about $200 | About $2,620 | About $1,220 | From $2,090 | About $1,195 | About $1,040 |
| 100 sq ft bump-out Building permit, Electrical permit, Mechanical permit | $1,925 plans, engineering & permits + engineer stamp about $200 | About $1,550 | About $540 | From $1,225 | About $690 | About $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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More permit guides: Decks · Retaining walls · Outdoor stairs · Porch & patio covers · ADUs & garage conversions · 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.