An ADU builder in Beaverton is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Beaverton's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Oregon.
What ADU Builders Cost in Beaverton [12][13]
Based on our Beaverton cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $165,000-$300,000 |
| Cost per Sq Ft | $200-$420 |
| Garage Conversion | $70,000-$160,000 |
| Prefab / Modular ADU (installed) | $100,000-$240,000 |
| City Permit & Plan Review | 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. |
| Impact Fees | System Development Charges from the city (transportation, water), Tualatin Hills Park & Recreation District, Clean Water Services (sanitary/stormwater) and Washington County (Transportation Development Tax) apply to a new dwelling unit; ADU treatment and any reductions are in the city's SDC handout B70-1116, unreachable on 9/20/2026. Ask the Site Development Division for a written SDC estimate before design. |
For a full line-item breakdown, see our Beaverton ADU cost guide. To confirm what you're allowed to build before you hire, review the Beaverton ADU rules (max detached size: 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).; owner-occupancy: Not required. Section 60.50.03 contains no owner-occupancy rule and ORS 197A.425(1)(b)(B) (formerly ORS 197.312(5)) prohibits cities from imposing one; the state exception lets cities restrict short-term rental of ADUs, so ask the city before listing the unit for stays under 30 days.).
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How to Vet an ADU Builder in Beaverton
- License: Confirm a current contractor's license in Oregon and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Beaverton and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (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.), plan check (Structural, energy, fire-separation and plumbing plan review is part of the building permit (Building Division); the land-use decision under 40.05.15 checks zoning only. Detached ADUs must be 6 ft from other buildings or meet the Residential Specialty Code's fire-separation rules.), and impact fees (System Development Charges from the city (transportation, water), Tualatin Hills Park & Recreation District, Clean Water Services (sanitary/stormwater) and Washington County (Transportation Development Tax) apply to a new dwelling unit; ADU treatment and any reductions are in the city's SDC handout B70-1116, unreachable on 9/20/2026. Ask the Site Development Division for a written SDC estimate before design.) are included.
- Permit handling: Confirm they manage Beaverton's permit process ("Two steps: (1) a Type 1 Accessory Dwelling Unit land-use application to the Community Development Director under Development Code 40.05.15 (no hearing, no neighbor notice; criteria are consistency with Chapters 20 and 60 and a complete submittal per 50.25), filed by the owner or agent through the Beaverton Electronic Permitting System (BEPS); then (2) a building permit with plumbing, electrical and mechanical permits, built to the Oregon Residential Specialty Code (60.50.03.2.E.4). A pre-application conference can be used to fix the submittal list (40.05.15.1.D).", typically Not published. The Type 1 ADU decision is made by the Director without a hearing (40.05.15.1.B; procedure in 50.35), then building plan review follows; confirm current turnaround times with Beaverton Planning and Building before scheduling a contractor.) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Beaverton in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (Not published. The Type 1 ADU decision is made by the Director without a hearing (40.05.15.1.B; procedure in 50.35), then building plan review follows; confirm current turnaround times with Beaverton Planning and Building before scheduling a contractor.) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Oregon ADU client references?
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