An ADU builder in Gilbert 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 Gilbert'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 Gilbert [11][12][13]
Based on our Gilbert 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 | Valuation-based: a $150,000 valuation is $1,145 permit plus $744.25 plan review (65% of the permit fee), about $1,890; add a $1,000 Administrative Use Permit if over 1,000 sq ft (Development Services Fee Schedule, Res. 4563 eff. July 1, 2025, revised Sept 15, 2026). |
| Impact Fees | System Development Fees for an ADU: $2,339.50 parks and recreation + $438.50 traffic signals + $752.50 roads + $284.50 police + $361.75 fire = $4,176.75, one quarter of the single-unit rate (adopted April 16, 2024, effective July 1, 2024). Water and wastewater connection fees ($18,396-$18,603 for a 3/4-inch meter) apply only if a new or larger meter is needed; ADU utilities normally come off the house, so confirm with the One Stop Shop (480-503-6728). |
For a full line-item breakdown, see our Gilbert ADU cost guide. To confirm what you're allowed to build before you hire, review the Gilbert ADU rules (max detached size: 75% of the primary home's gross floor area (interior habitable area), measured by LDC Section 2 'Gross Floor Area'. Up to 1,000 sq ft is by right; from 1,001 sq ft up to the 75% cap the unit needs a $1,000 Administrative Use Permit and must be inside the building envelope (LDC 5.2.3.4.c, 5.2.3.A-B). State floor: the lesser of 75% or 1,000 sq ft must be permitted (ARS 9-461.18.A.3).; owner-occupancy: Not required. LDC 5.2.3.4.f allows the ADU to be rented separately from the house, and ARS 9-461.18.B.1-2 bars any owner-residency or family-relationship test for long-term rentals (90 days or longer, or month to month). Short-term rentals need a Town STR licence (see rental).).
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How to Vet an ADU Builder in Gilbert
- 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 Gilbert 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 (Valuation-based: a $150,000 valuation is $1,145 permit plus $744.25 plan review (65% of the permit fee), about $1,890; add a $1,000 Administrative Use Permit if over 1,000 sq ft (Development Services Fee Schedule, Res. 4563 eff. July 1, 2025, revised Sept 15, 2026).), plan check (Full construction plan review through the One Stop Shop; a soils report is required unless the subdivision has one on file or you sign the Town's soils waiver; a third or later review may be billed at $150 per hour; expedited review costs twice the plan-review fee (Fee Schedule pp. 8-9; ADU Guide).), and impact fees (System Development Fees for an ADU: $2,339.50 parks and recreation + $438.50 traffic signals + $752.50 roads + $284.50 police + $361.75 fire = $4,176.75, one quarter of the single-unit rate (adopted April 16, 2024, effective July 1, 2024). Water and wastewater connection fees ($18,396-$18,603 for a 3/4-inch meter) apply only if a new or larger meter is needed; ADU utilities normally come off the house, so confirm with the One Stop Shop (480-503-6728).) are included.
- Permit handling: Confirm they manage Gilbert's permit process ("By-right building permit through the Development Services One Stop Shop (electronic plan review) for an ADU up to 1,000 sq ft; over 1,000 sq ft, obtain a $1,000 Administrative Use Permit from Planning first. Plans must show front-elevation articulation (all sides on two-story units), ground-mounted screened mechanical equipment and utilities fed from the house's service (LDC 5.2.3.5; Town ADU Guide).", typically Published review goals: 12 working days for the first review of a single-family plan set and 8 for the second (room additions 8/4); Express Permitting reviews eligible detached residential structures in 1-3 working days for the plan-review fee plus 60% (Project Review Time Frames, Mar 2026).) 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 Gilbert 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 (Published review goals: 12 working days for the first review of a single-family plan set and 8 for the second (room additions 8/4); Express Permitting reviews eligible detached residential structures in 1-3 working days for the plan-review fee plus 60% (Project Review Time Frames, Mar 2026).) 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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