ADU Permit Requirements in Forest Grove, OR
City runs its own delegated building program (Forest Grove/Cornelius Building Division) and issues structural, mechanical, and plumbing permits enforcing the statewide Oregon specialty codes; permits pulled through the State of Oregon ePermitting (Accela) portal. Verified exemption thresholds: deck exempt if not over 30 in above grade and 5 ft from property lines; fence exempt if not over 6 ft (pool barriers regulated); accessory building exempt if not over 200 sq ft (or frame-covered up to 500 sq ft, one story, 5 ft from lines); reroof exempt if not over 30% of live-load capacity and not required to be fire-resistant. Office hours not published online.
By Joey, Founder · Last verified May 31, 2026 · How we research →
When you need a ADU permit
An accessory dwelling unit (ADU) requires a building permit plus electrical, plumbing, and mechanical permits, enforced by the City of Forest Grove Building Division under the 2023 Oregon Residential Specialty Code. Oregon state law (SB 1051) requires cities to allow at least one ADU on lots zoned for single-family use. Plans are submitted through the State of Oregon ePermitting (Accela) portal; zoning and setback review applies.
ADU Permit Costs: Forest Grove vs. Nearby
| City | Estimated Fee |
|---|---|
| Forest Grove | N/A |
| Portland | $750 – $7,500 |
| Lane County | $750 – $7,500 |
| Salem | $750 – $7,500 |
Fees shown are estimates based on local building code data. Actual fees may vary based on project scope and valuation. See all Forest Grove permit costs →
Zoning Considerations
ADU regulations vary dramatically by state and city. Many states (CA, OR, WA) have preemption laws that override local zoning restrictions. Check both state law and local zoning before designing.
Estimated Project Timeline
Here's a typical timeline for a adu project:
Timeline is based on the typical about 4 weeks permit processing time. Actual timelines vary by project complexity, completeness of application, and current department workload.
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Frequently Asked Questions
Contact the building department for current ADU permit fee information. Fees typically vary based on project scope and valuation.
It depends on the specifics of your project. Some smaller ADU projects may be exempt from permit requirements, while larger ones typically require a permit. Use our free lookup tool to check your specific situation.
Working without a required permit can result in fines, stop-work orders, being required to remove completed work, and complications when selling your home. It's always best to check first.
Typical approval time for ADU permits is about 4 weeks. More complex projects may take longer if plan review is required.
Learn More About ADU Permits
Read our complete guide covering permit requirements, costs, common exemptions, and the application process.
Read ADU Guide →