Do I Need a Permit to Build an ADU in Phoenix, AZ?

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Conditions

Full permit conditions

All 8 conditions for Phoenix adu permits.

Phoenix allows ADUs on single-family lots, but the project still needs normal building-permit review through Planning & Development. State preemption did not eliminate permits; it limited what the city can prohibit or require.
Arizona HB 2720 now requires large municipalities to allow at least one attached, detached, or internal ADU as a permitted use on any lot where a single-family dwelling is allowed. Phoenix updated its ordinance in late 2024 to comply.
Under state law, an ADU may be up to 75% of the gross floor area of the primary single-family dwelling or 1,000 square feet, whichever is less.
Phoenix cannot require owner occupancy, cannot require additional parking or parking-in-lieu fees for an ADU, and cannot require a family or employment relationship between the main-house occupant and ADU occupant.
Phoenix also cannot impose rear or side setbacks greater than 5 feet for ADUs, and it cannot make ADU height, setback, lot-size, coverage, or frontage standards more restrictive than those applied to single-family dwellings in the same zoning area.
Long-term rental use is protected by state law. A municipality may not prohibit separately leasing the main house and the ADU for long-term rentals of at least 90 days or month-to-month occupancy.
Building-code, fire-code, and public-health rules still apply. The state law expressly preserves those requirements, except that Phoenix cannot force an ADU into a commercial code path or require a fire sprinkler solely because it is an ADU.
Historic Preservation overlays, floodplain conditions, utility easements, and HOA rules can still affect project design or approvals even though the base ADU entitlement is now broadly protected.

Fees

Estimated city fees

Baseline for a simple permitted adu: $1,500–$6,500+ is a realistic Phoenix planning range for an ADU permit package including building review, plan check, and trade permits

Fee	Amount	Notes
Residential building permit	$1,500–$6,000+ (estimated range)	Phoenix calculates permit fees from project valuation. Detached new-build ADUs and major additions cost more than internal conversions.
Plan review fee	~65% of the building permit fee	Phoenix's published plan-review structure typically tracks a percentage of the permit fee for residential work requiring plan check.
Trade permits (electrical, plumbing, mechanical)	$150–$900+ each depending on scope	Habitable second units require separate trade review and inspections.
Historic Preservation or floodplain review	Varies by parcel	Overlay review and civil/site issues can add time and cost even though the ADU itself is a protected permitted use.

Documents

Required documents

Residential building permit application submitted through Phoenix's online permitting system / SHAPE PHX.
Site plan showing lot lines, primary dwelling, proposed ADU location, setbacks, easements, and utility routing.
Architectural floor plans and elevations for the attached, detached, or internal ADU.
Structural plans and foundation details as required by Phoenix for habitable residential construction.
Electrical, plumbing, mechanical, and energy-compliance documents for the dwelling unit.
Historic Preservation approvals if the property is in an HP overlay district.
Floodplain or drainage materials if the lot has site-development constraints.
Any manufacturer data or delegated engineering for prefab or standard-plan components used in the ADU.

Timeline

Typical timing

Plan review: 10–20 business days for a complete residential ADU submittal
Total cycle: 2–6 months for many Phoenix ADU projects from design-ready submission through final inspection

Phoenix's land-use path is cleaner after HB 2720, but engineering quality, overlay review, and permit completeness still determine speed.

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Process

How the permit process works

Confirm the lot is a single-family parcel and pick the ADU type Phoenix now has a broad state-preemption backdrop, so the main early question is project type and site fit rather than whether ADUs are categorically banned.
Size the ADU to the state cap Check the gross floor area of the primary dwelling, then keep the ADU at 75% of that gross floor area or 1,000 square feet, whichever is less.
Lay out setbacks, utilities, and overlays State law prevents Phoenix from demanding rear or side setbacks above 5 feet for ADUs, but you still need a buildable site outside easements, with workable utilities and any historic/floodplain issues addressed.
Prepare a residential permit plan set Create full permit drawings for the ADU. State preemption gives you the land-use path; it does not waive building-code review.
Submit through Phoenix Planning & Development File the residential permit application through the City portal, upload plans, and respond to intake or plan-review comments.
Pull trade permits and receive issuance After the main plan set is approved, handle electrical, plumbing, and mechanical permits and pay the permit and plan-review fees.
Build, inspect, and close out Schedule required inspections and keep the permit record. Phoenix's friendlier ADU entitlement still expects full compliance at the construction stage.

Code basis

What Phoenix reviews against

Arizona Revised Statutes Section 9-461.18 as enacted by HB 2720 (2024) and Phoenix's conforming ADU ordinance changes; Phoenix Planning & Development ADU guidance and beginner materials; Phoenix residential building-permit review requirements.

Residential permit page Phoenix permit portal

If you skip the permit

What can go wrong

Phoenix can stop work and force after-the-fact permitting if you build a second dwelling without the required permit approvals.
State preemption helps with entitlement, but it does not excuse structural, electrical, plumbing, or life-safety compliance.
If you size the ADU above the statutory cap, the project will hit avoidable redesign and review delays.
Ignoring easements, floodplain constraints, or HP overlays can derail a seemingly easy Phoenix ADU late in the process.
Unpermitted habitable space creates resale and insurance friction because the second dwelling lacks a clean city record.
Treating long-term-rental protection as permission for short-term rental use is a mistake; state law speaks to long-term rental, not blanket STR authorization.

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