Arizona is one of the most ADU-friendly states in the country — and recent legislation has made it even easier for Phoenix-metro homeowners to add a casita, rental unit, or in-law suite. If you have been thinking about it, the regulatory environment has shifted significantly in your favor. This guide covers what the law actually says, what you can build in your city, what it costs, and how to get it permitted.
What Arizona Law Actually Says: HB 2928 (2024)
The law that defines ADU rights for most Phoenix-metro homeowners today is HB 2928, signed in 2024. It applies to municipalities with a population over 75,000 and sets a statewide floor that cities cannot go below. Here is what it actually requires and prohibits:
What Cities Must Allow
- At least one attached and one detached ADU as a permitted use on any single-family lot. If you own a home on a residential lot in a qualifying city, you have a legal right to build an ADU — the city cannot deny it outright.
- An ADU up to 75% of the primary home's square footage, or 1,000 sqft, whichever is less — as a guaranteed minimum. Cities can allow larger ADUs but cannot set the maximum below this floor.
What Cities Cannot Do
- Ban ADUs outright on single-family lots in qualifying cities.
- Require owner-occupancy for long-term rentals. If you lease your ADU for 30 days or more, cities cannot require you to live on the property. You can build a casita on a rental property you do not occupy and lease it long-term.
- Require additional parking. Cities cannot require extra off-street parking spaces for ADUs, nor charge parking fee waivers.
- Require family or employment relationships between the primary homeowner and the ADU occupant.
- Set rear or side setbacks greater than five feet from the property line for ADUs.
- Require ADUs to match the primary home's exterior design, roof pitch, or finishing materials.
The Short-Term Rental Exception
One important nuance: if you plan to use an ADU built after September 14, 2024 as a short-term rental (under 30 days), cities retain the right to require owner-occupancy on the property. This applies only to STR use — long-term leases of 30+ days are not subject to this requirement. If STR income is part of your plan, verify your specific city's current stance before committing to a build.
ADU Types You Can Build in Arizona
- Detached ADU (Casita): A fully separate structure in the backyard. Most popular option for rental income and guest use. Highest cost but maximum flexibility and privacy.
- Attached ADU: An addition built onto the existing home with its own entrance, kitchen, and bath. Lower cost than detached but shares a wall with the primary residence.
- Garage Conversion: Converting an attached or detached garage into livable ADU space. Lowest cost option since the structure already exists.
- Junior ADU (JADU): Up to 500 sqft created within the existing footprint of the primary home — typically a converted bedroom with a kitchenette and separate entrance. Fastest permits, lowest cost.
City Requirements by City (2025)
HB 2928 sets the statewide floor, but each city sets its own standards within those limits. Here is where the major Phoenix-metro cities stand in 2025. Note that these numbers reflect what cities currently allow or require — some are more permissive than the state minimum, some are at the floor.
| City | Max ADU Size | Rear Setback | Side Setback | Max Height |
|---|---|---|---|---|
| Scottsdale | 1,200 sqft or 50% of primary home | 10 ft | 5 ft | 18 ft |
| Phoenix | 1,000 sqft (detached) | 5 ft | 5 ft | 24 ft |
| Tempe | 1,200 sqft | 5 ft | 5 ft | 20 ft |
| Gilbert | 1,200 sqft | 10 ft | 5 ft | 18 ft |
| Chandler | 1,000 sqft | 10 ft | 5 ft | 18 ft |
| Mesa | 1,200 sqft | 5 ft | 5 ft | 20 ft |
| Paradise Valley | 800 sqft or 25% of primary home | 20 ft | 10 ft | 14 ft |
| Peoria | 1,200 sqft | 10 ft | 5 ft | 20 ft |
City codes update regularly. Always verify current requirements with the city's development services department or your licensed contractor before finalizing plans.
The ADU Permit Process in Phoenix Metro
ADU permits in most Phoenix-area cities run through the standard residential building permit pathway. Here is a realistic timeline from decision to move-in:
- Weeks 1–2 — Feasibility: Confirm setbacks, lot coverage limits, utility availability, and any HOA restrictions. A licensed contractor can do this quickly, often at no charge.
- Weeks 2–6 — Plans: Architectural drawings prepared. Most ADUs under 1,000 sqft do not require a licensed architect — a qualified designer or drafter works. Larger or more complex builds may require full architectural and structural drawings.
- Weeks 4–10 — Permit Review: Application submitted and under city review. Phoenix, Tempe, and Mesa offer expedited ADU review programs — some approvals in as little as 3–4 weeks. Scottsdale and Gilbert typically run longer.
- Weeks 12–30 — Construction: Most detached casitas complete in 12–18 weeks from permit approval. Garage conversions and JADUs typically run 8–12 weeks.
What an ADU Costs in Phoenix in 2025
All-in costs for Phoenix-metro ADU construction in 2025, based on current market conditions:
| ADU Type & Size | Cost Range | What's Included |
|---|---|---|
| Junior ADU / JADU (300–500 sqft) | $30,000 – $65,000 | Within existing home footprint. Kitchenette, separate entrance, minimal structural work. |
| Garage Conversion (450–650 sqft) | $45,000 – $95,000 | Existing structure converted. HVAC, insulation, plumbing rough-in, finishes. |
| Studio Casita (350–500 sqft) | $75,000 – $130,000 | New detached build. Kitchenette, 1 bath, mini-split HVAC, separate electrical meter. |
| 1BR Casita (500–700 sqft) | $110,000 – $185,000 | Full kitchen, 1 bath, separate electrical, covered entry or patio. |
| 2BR Casita (750–1,000 sqft) | $160,000 – $260,000 | Full kitchen, 2 bath, laundry connections, separate utility meters. |
Costs vary based on finish level, site conditions, and city permit fees. Caliche removal, utility connection distance, and HOA-mandated exterior finishes can all push costs toward the top of the range.
Does the Investment Make Sense?
A 600 sqft casita in Tempe or Mesa, renting at $1,400–$1,600/month, generates $16,800–$19,200/year in gross rental income. At a construction cost of $140,000, that is roughly an 8–9 year payback on the build cost alone — before accounting for property value appreciation and equity gains.
In higher-rent submarkets like Scottsdale and Paradise Valley, the math compresses further. A well-built casita in a desirable zip code can generate $1,800–$2,500/month depending on size and finishes.
The builds that do not pencil: oversized casitas in lower-rent submarkets, or builds where site conditions (caliche, long utility runs, HOA exterior requirements) push construction cost significantly above the median. A quick feasibility assessment before you commit to plans will tell you whether your specific property makes sense.
Financing Options
- HELOC or home equity loan: The most common path for homeowners with equity. Borrow against your home, repay over time. Rates vary with the market.
- Cash-out refinance: Pull equity out of your primary mortgage to fund construction. Less attractive if your current rate is significantly below today's rates.
- Construction loan: Short-term financing that funds construction in draws, then converts to a permanent mortgage. More complex to qualify for but useful if you have limited existing equity.
- FHA 203k or Fannie Mae HomeStyle: Government-backed renovation loan products that allow you to roll construction financing into one loan. Works on purchases and refinances.
The HOA Wildcard
HB 2928 governs what cities and towns can require — it does not override private HOA covenants, conditions, and restrictions (CC&Rs). If your property is in an HOA, the CC&Rs can still prohibit ADUs, restrict rentals, mandate exterior materials, or require architectural review approval regardless of what state law says.
Pull your CC&Rs before you spend money on plans. Look specifically for language about secondary structures, accessory buildings, rental restrictions, and occupancy limits. Some HOAs prohibit only short-term rentals while allowing long-term ADU leases. Others prohibit additional dwelling units entirely. Know which category you are in before you commit to anything.
Bottom Line
The regulatory environment for ADUs in Arizona is as favorable as it has ever been. HB 2928 removed the biggest legal barriers and forced cities to allow what previously required variances or exceptions. The question is no longer whether you can build — it is whether your specific lot, city, and HOA situation makes it practical, and whether the economics work for your goals.
A free feasibility assessment answers all of those questions before you spend a dollar on plans. We cover setbacks, lot coverage, city permit timeline, and a realistic cost range for your specific property.