Compare ADU zoning rules across 5 Oregon cities. Average ADU score: 8.2/10.
Gathered from the 5 cities below, with the bill or ordinance each one names. Statewide measures are listed once with the cities they reached, rather than repeated for each.
Statewide law sets a floor; the numbers that decide your project are local. Here is the spread across the 5 Oregon cities covered here, taken from each city's own ordinance rather than a state summary.
| Question | Across Oregon |
|---|---|
| Are ADUs permitted? | 5 of 5 permit them. |
| Detached size cap | Median 600 sq ft, from 300 to 800 sq ft across the 5 cities publishing a numeric cap. |
| Owner-occupancy | Required in none of them. |
| Build cost | $110,000 to $350,000 depending on city and unit type. |
| Easiest and hardest here | Portland scores 9/10; Salem scores 8/10. |
Recomputed whenever a city page changes, so this and the city pages below cannot disagree.
| City | Max Size | Setbacks | Permit Fees | Build Cost | 1BR Rent | Score |
|---|---|---|---|---|---|---|
| Beaverton | 800 sq ft of floor area (60.50.03.2.C.1). No percentage-of-house rule. A detached ADU can be a new building or a manufactured home (60.50.03.2.B.3). An ADU added to a house that existed on June 30, 2022 is excluded from the zone's floor-area-ratio cap (60.50.03.2.C.4); an ADU built with a new house counts toward FAR (1.40 RMA, 0.80 RMB, 0.60 RMC for single-detached, Table 20.05.15.H.1). | 15 ft in RMA, RMB and RMC (Table 20.05.15.F.3), reduced to 5 ft for a one-story ADU no taller than 15 ft measured from finished grade (60.50.03.2.E.2). No ADU may be placed over any easement (60.50.03.2.E.3). | The ADU land-use fee is set in the Citywide Comprehensive Fee Schedule (Exhibit A to the fee resolution) and the building permit is valuation-based (Building Permit Fee Schedule B70-1108); both PDFs were behind a bot check on 9/20/2026, so confirm current figures with Community Development. | $165,000-$300,000 | $1,400-$1,650/mo | 8/10 |
| Bend | 800 sq ft floor area for a single ADU; where two ADUs are built, one may be up to 800 sq ft and the other up to 500 sq ft (BDC 3.6.200(B)(3)(a)). Floor area is measured inside the exterior walls, stairs count once, and space under a ceiling lower than 5 ft is excluded (B)(3)(b). An attached garage or storage room does not count if it has no interior access to the ADU or provides the ADU's parking space (B)(3)(d). A unit over 800 sq ft is reviewed as a duplex, not an ADU. | No ADU-specific setback; the underlying zoning district's rear setback applies (City ADU Zoning Quick Reference Guide: 'Building Setbacks: follow your zoning district's rules'). A detached ADU must sit at least 6 ft from any other dwelling on the lot, measured footprint to footprint (BDC 3.6.200(B)(5); exempt when each structure was legally built before April 1, 2016). | Roughly $3,000-$4,000 for a 600-800 sq ft ADU at FY2025-26 rates: building permit $1,212.58 for the first $100,000 of valuation + $7.00 per extra $1,000, plan review 65%, 12% state surcharge, 0.33% affordable-housing fee, plus trade permits. The City emails project estimates. | $225,000-$350,000 | $1,600-$2,000/mo | 8/10 |
| Eugene | 800 sq ft or 10% of lot area, whichever is smaller, measured at the exterior walls and including halls, closets, stairs and baths (EC 9.2751(17)(a)1). Up to 300 sq ft of attached unheated garage or storage is not counted (800 sq ft if the ADU is above a garage). In the R-1 zone inside Amazon Neighbors, Fairmount Neighbors or South University: 600 sq ft on lots under 9,000 sq ft, 800 sq ft on lots of 9,000 sq ft or more (EC 9.2751(17)(c)2) | 5 ft (Eugene treats side and rear lot lines alike as 'interior yard' setbacks; EC 9.2751(17)(a)2 and (b)4). Eaves and chimneys may project 2 ft into it. On a flag lot the interior setback is 10 ft (EC 9.2775(5)(e)). An ADU above a garage may sit closer with a 10 ft building separation and a recorded maintenance-access easement (EC 9.2751(17)(a)2.c) | Valuation-based: building permit $953.34 plus $4.34 per $1,000 over $100,000, plan check 65% of that (waived for pre-approved plans), electrical $244.40, plumbing $571.40 for one bath, mechanical per appliance, plus 12% state surcharge (schedule effective July 1, 2025; a July 2026 schedule applies) | $110,000-$285,000 | $1,200-$1,500/mo | 8/10 |
| Portland | 800 sq ft of living area or 75% of the main home's living area, whichever is less, measured after the ADU is built (33.205.040.C.1). Living area excludes exterior walls, garages and basement space under a 6 ft 8 in ceiling. Building coverage also cannot exceed the main house's, and all accessory structures together may cover at most 20% of the lot (33.110.245.C.3) | 5 ft in R7, R5 and R2.5; 10 ft in RF, R10 and R20 (Table 110-4). In R7/R5/R2.5 a detached ADU may sit on the rear lot line (0 ft) if it is at least 40 ft from the front lot line, no more than 15 ft tall with 10-ft walls, within a 24 x 24 ft footprint, has no doors or windows facing that lot line and keeps dormers 5 ft off it (33.110.245.C.2.b) | Building permit and plan-review fees are valuation-based under the Building and Other Permits Fee Schedule effective July 10, 2026 (no flat ADU fee); trade permits are separate. SDCs: Parks $7,941 (under 700 sq ft) or $11,878, Transportation $3,421, waived with the 10-year no-STR covenant | $180,000-$280,000 | $1,400-$1,700/mo | 9/10 |
| Salem | 900 sq ft or 75% of the main building's gross floor area, whichever is less (SRC 700.007; City ADU and Middle Housing pages, read Sept 2026). The City's free ready-build plan is under 600 sq ft | Not published on the City's ADU page; SRC 700.007 and the zone's accessory-building standards govern (Municode text could not be read in Sept 2026 - bot wall). Confirm with the Planners Desk, 503-588-6213, before drawing the site plan | Valuation-based (FY2027 Fee Schedule Section 3): $645 for the first $100,000 plus $3.95 per $1,000, plan review 65% of that, a 12% state surcharge, plus trade permits - roughly $1,600-$2,100 for a 600-900 sq ft ADU valued at $175.92/sq ft. SDCs: $0. | $170,000-$330,000 | $1,100-$1,400/mo | 8/10 |
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