An ADU builder in Tempe 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 Tempe's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Arizona.
What ADU Builders Cost in Tempe [11][12][13][14]
Based on our Tempe 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) | $150,000-$280,000 |
| Cost per Sq Ft | $175-$350 |
| Garage Conversion | $80,000-$150,000 |
| Prefab / Modular ADU (installed) | $150,000-$300,000 |
| City Permit & Plan Review | Building permit fee is valuation-based per City Code Fee Schedule Table 1-A, plus a plan review fee of 65% of the permit fee (Community Development Service Fees sheet); the Residential Rebate Program refunds 100% of both after final inspection. |
| Impact Fees | Tempe's fee page lists General Government Development Fees (impact fees) and water/sewer fees in the City Code fee appendix on Municode; no ADU-specific exemption is published, and impact, planning, fire and water/sewer fees are not covered by the Residential Rebate. Ask the Permit Center (480-350-4311) for the ADU amount; ARS 9-461.18(B)(3) bars parking in-lieu fees. |
For a full line-item breakdown, see our Tempe ADU cost guide. To confirm what you're allowed to build before you hire, review the Tempe ADU rules (max detached size: Lots under 1 acre: 75% of the main house's gross floor area or 1,000 sq ft, whichever is less. Lots of 1 acre (43,560 sq ft) or more: 75% or 2,000 sq ft, whichever is less. Gross floor area is interior habitable area, excluding garages, carports and exterior storage (ZDC 3-402; ADU Development Guide Step 2). District lot coverage still applies, e.g. 45% in R1-6.; owner-occupancy: Not required for long-term rentals, and the city may not demand a family or employment relationship (ARS 9-461.18(B)(1)-(2)). One exception: an ADU built on or after December 20, 2024 that is licensed as a short-term rental requires the owner to live on the property (Tempe City Code 16A-213(k), authorized by ARS 9-500.39(B)(9)).).
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How to Vet an ADU Builder in Tempe
- License: Confirm a current contractor's license in Arizona 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 Tempe 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 (Building permit fee is valuation-based per City Code Fee Schedule Table 1-A, plus a plan review fee of 65% of the permit fee (Community Development Service Fees sheet); the Residential Rebate Program refunds 100% of both after final inspection.), plan check (Plan review fee is 65% of the building permit fee, paid at submittal; it covers the first review plus two resubmittals (a fourth review costs extra). Submit through E-Plan Review; first-review target 5-10 working days.), and impact fees (Tempe's fee page lists General Government Development Fees (impact fees) and water/sewer fees in the City Code fee appendix on Municode; no ADU-specific exemption is published, and impact, planning, fire and water/sewer fees are not covered by the Residential Rebate. Ask the Permit Center (480-350-4311) for the ADU amount; ARS 9-461.18(B)(3) bars parking in-lieu fees.) are included.
- Permit handling: Confirm they manage Tempe's permit process ("Building permit only, filed online through the Tempe Citizen Access Portal with a site plan, floor plans (including the existing house) and construction documents per the Residential Building Permit Checklist; no hearing or use permit for a one-story ADU (ARS 9-461.18(I)(5)). A two-story design needs a Use Permit (Board of Adjustment decision, Dec 17, 2025). Each ADU gets its own address (e.g. 1234 B) in 4-inch numbers.", typically Target first residential plan review of 5-10 working days for projects under $500,000 and 4-6 working days per resubmittal (Building Safety Target Turn-Around Times, revised Aug 26, 2025); residential engineering review 5-15 working days.) 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 Tempe 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 (Target first residential plan review of 5-10 working days for projects under $500,000 and 4-6 working days per resubmittal (Building Safety Target Turn-Around Times, revised Aug 26, 2025); residential engineering review 5-15 working days.) 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 Arizona ADU client references?
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