How many ADUs can I build in Phoenix?

Where a lot has no more than one single-family detached primary dwelling, Phoenix allows up to two ADUs in addition to the primary dwelling (a third may be permitted under certain circumstances). Each ADU may be up to 75% of the main house's gross floor area, capped at 1,000 sq ft (lots up to 10,000 sq ft) or 3,000 sq ft (larger lots). Source: City of Phoenix Accessory Dwelling Units page, phoenix.gov.

Accessory Dwelling Unit (ADU) Permit in Phoenix, Arizona

An Accessory Dwelling Unit (ADU) — also called a guest house, casita, or granny flat — is a separate, self-contained living area, either fully detached or attached to an existing home, with its own kitchen, bathroom, living area and sleeping quarters. In late 2024 the Phoenix City Council approved ordinance changes to comply with new state ADU laws. Where a lot has no more than one single-family detached primary dwelling, two ADUs are permitted in addition to the primary dwelling (a third may be permitted under certain circumstances). Phoenix offers a free pre-approved ADU Standard Plan Library; a plot/site plan is still required for permitting.

Verified 2026-06-29 · Source

When you need this permit

Permitted where a lot has no more than one single-family detached primary dwelling: up to two ADUs in addition to the primary dwelling (a third ADU may be permitted under certain circumstances)
Each ADU may be up to 75% of the gross floor area of the main house, not to exceed 1,000 sq ft for lots up to 10,000 sq ft, or 3,000 sq ft for lots over 10,000 sq ft
Must comply with the zoning district's lot-coverage guidelines (typical single-family zones include R1-6, R1-10)
A plot/site plan is required for permitting (even when using a pre-approved ADU Standard Plan)
Pre-approved ADU Standard Plans are free to City of Phoenix residents but must be submitted as-is without modifications (changes require a new submittal)

Required documents

Req
Residential Construction Permit / Plan Review Application (TRT/DOC/00030)
Universal residential application used to permit an ADU; available on the PDD Residential Applications & Checklists page
Req
Plot / Site Plan
Required for ADU permitting even when using a pre-approved standard plan
Opt
ADU Standard Plan (optional)
Pre-approved detached ADU design from the ADU Standard Plan Library; free to residents, submitted as-is

Fee schedule

Fee type	Amount	Notes
ADU building permit — valuation-based (Table A)	Per valuation-based Table A (e.g. a typical ADU valued in the $50,001–$200,000 range = $703 on first $50,000 plus $9 per additional $1,000), plus applicable plan review fee	PDD Fee Schedule, Table A (Ordinance G-7465, effective 1/20/2026). Phoenix does not publish a separate ADU-specific fee; the ADU is permitted as a residential structure under Table A.

Review timeline

~10–30 business days

Typical estimate — confirm current times with the Phoenix building department

Inspection process

1
Pre-pour / footing
Underground plumbing/electrical, rebar, hold-downs, footing depth/width, and UFER grounding before concrete is poured (for detached ADUs)
2
Rough trades / framing
Rough plumbing, mechanical, and electrical, and framing inspected before insulation and drywall
3
Final
All work complete per approved plans; fixtures, devices, and equipment inspected at final

Tips

Phoenix updated its ADU ordinance in late 2024 to comply with new Arizona state ADU laws — up to two ADUs are now allowed on a typical single-family lot.
Each ADU may be up to 75% of the main house's gross floor area (capped at 1,000 sq ft for lots up to 10,000 sq ft, 3,000 sq ft for larger lots).
Pre-approved ADU Standard Plans are free but must be used as-is; any modifications require a new submittal.
Find your lot size on the Maricopa County Assessor's Office website to estimate lot coverage before designing your ADU.

Frequently asked questions

How many ADUs can I build in Phoenix?: Where a lot has no more than one single-family detached primary dwelling, Phoenix allows up to two ADUs in addition to the primary dwelling (a third may be permitted under certain circumstances). Each ADU may be up to 75% of the main house's gross floor area, capped at 1,000 sq ft (lots up to 10,000 sq ft) or 3,000 sq ft (larger lots). Source: City of Phoenix Accessory Dwelling Units page, phoenix.gov.

Sources & verification

Verified against official sources. Last reviewed 2026-06-29.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Phoenix building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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