How much does an ADU cost in Phoenix?

As of October 2026, a 2026 Arizona cost guide puts a 600 sq ft detached casita in Phoenix at about $120,000 basic, $160,000 to $220,000 mid-range and $330,000 or more high-end. A Phoenix-area builder's July 2026 ranges are higher: $150,000 to $250,000 for conversions and small attached units, $400,000 and up for fully finished detached ADUs.

What does each ADU type cost around Phoenix?

The two sources measure different things. The cost guide prices a fixed 600 sq ft casita by finish level; the builder prices whole projects it has scoped. Neither is our price. We give a written, itemized quote after seeing your lot.

What costs sit outside the construction price?

• Utilities. About $15,000 on a favorable lot to $50,000 or more on a difficult one, per one Phoenix-area builder.
• Permits and impact fees. A 2026 cost guide estimates Phoenix permits for a 600 sq ft casita at about $4,500. Glendale publishes about $12,184 to $13,034 for a 1,000 sq ft ADU, mostly impact fees.
• Caliche. The same cost guide lists $5,000 to $20,000 for caliche removal on affected lots.
• Cooling. It adds $6,000 to $14,000 for heat-rated HVAC, which its base prices leave out.
• Kitchen. A full kitchen runs $25,000 or more above a kitchenette, per the builder.
• Replacement parking. A new dustproof pad when a Phoenix garage is converted.

Does Arizona cap ADU impact fees?

No. Arizona's ADU law limits parking, setbacks and street improvement demands, but it does not exempt small ADUs from impact fees. Each city sets its own. Glendale, for example, charges single-family impact rates for detached ADUs and multifamily rates for attached ones.

Why are Phoenix ADU bids so far apart?

It depends on what each bid includes. Before comparing, ask every builder to show in writing:

• whether design, engineering and city fees are included or excluded
• the utility scope, and the point on the lot where it stops
• the cooling system type and capacity
• allowances for cabinets, flooring and fixtures, and what happens if you go over
• who pays for a second or third round of plan corrections

What makes a Phoenix ADU cost more or less?

• Size and kitchen. A studio with a kitchenette costs far less than a two-bedroom with a full kitchen.
• Distance to utilities. A casita in the far corner of a deep lot needs a long trench.
• Electrical capacity. Older homes often need a service upgrade to carry a second air conditioner.
• Soil. Caliche can turn a day of footing work into a week.
• HOA requirements. Matching roof tile, stucco and paint can add cost the city does not require.

How do I get a number for my lot?

Use the lot check form to send your address. We check what your lot allows, visit, and then quote in writing, item by item. Also read how much rent an ADU can make to weigh the cost against income.