What a casita really costs in Arizona

The short version

• Per square foot in metro Phoenix: roughly $150 to $300+.
• Typical detached casita, all-in: $150,000 to $300,000.
• Attached / conversion (garage, basement, addition): can start around $50,000 to $90,000.
• Timeline after permits: 3–6 months construction.

Anything below $150/sq ft in Phoenix in 2026 is either a garage conversion, a prefab shell without utilities, or a bid that's about to have change orders. Anything above $300/sq ft usually reflects custom finishes, a second story, difficult site work, or a designer-led project.

What's actually in the number

Hard costs (materials + labor)

Foundation, framing, roof, stucco, drywall, flooring, cabinets, fixtures, HVAC, appliances. This is usually 60–70% of the total.

Utility runs

Extending sewer, water, and electrical to a new detached structure can add anywhere from a few thousand dollars to $30,000+ depending on distance from the main house and whether you need to trench through paved areas. This is one of the biggest surprises on real bids.

Site work

Grading, retaining walls, drainage, and demo of anything currently on the pad. Flat, empty backyards are cheap. Sloped lots or lots with mature landscaping to remove get expensive fast.

Design and permits

Architectural drawings, structural engineering, and city permits typically run $5,000 to $20,000 combined. Some builders roll this into the total; some don't. Ask.

General contractor fee

A licensed GC usually charges 10–20% on top of hard costs for management, insurance, warranty, and overhead. On a $200,000 build, that's $20,000 to $40,000 of the total.

Impact fees and utility hookup fees

These vary by city. Some cities have reduced or waived impact fees for ADUs under the new state framework; others still charge. Confirm with your city's planning department.

Realistic scenarios

Scenario A: Garage conversion in central Phoenix

400 sq ft, existing electrical and plumbing rough-in nearby, no HOA. Realistic all-in: $60,000–$95,000.

Scenario B: 1,000 sq ft detached casita in Mesa or Chandler

Standard lot, one-story, mid-range finishes, moderate utility runs. Realistic all-in: $180,000–$260,000.

Scenario C: 1,000 sq ft custom casita in Scottsdale

HOA architectural review, matching materials, upgraded finishes, some site work. Realistic all-in: $250,000–$350,000+.

How the money actually gets paid out

Casitas are almost never paid in one check. Real financing is drawn in stages against progress: foundation, framing, dry-in, mechanicals, finish, final. Each draw is inspected before the lender releases funds. That's how construction and renovation loans are structured — and it's why lining up financing before you sign a builder contract matters. See our financing guide for how HELOCs, cash-out refis, renovation loans, and construction-to-permanent loans compare. Also read the state ADU law so you know what your city can and can't charge you for.

Cost mistakes I see all the time

• Underestimating utility runs. The trench from your main panel to the backyard is not free.
• Skipping the survey. Setbacks are 5 feet minimum. Guessing where your property line is costs more than a survey.
• Trusting a fixed-price quote without a scope. "Turnkey" means whatever the contractor decides it means unless a spec sheet is attached.
• Forgetting furnishings. A finished casita is not a rentable casita. Add $5–15K for basic furniture if it's a rental.

Frequently asked questions