2026 cost guide · Phoenix, AZ
How much does it cost to build an ADU in Phoenix, AZ?
Typical range for a detached accessory dwelling unit
$186,000 – $346,000
About $361/sq ft midrange across 700 sq ft. Phoenix, AZ indexes at ×0.95 versus the national building-cost average — a city-level match in our cost index.
These figures come from the same estimating engine we use to price a real project — the local cost index for Phoenix, AZ is baked in, not a national average with your city's name pasted on top. The number that matters is your project’s, though: finish level, site, and scope move it more than geography does. Get your exact adu / guest house estimate →
ADU / guest house cost by finish level in Phoenix, AZ
Starter / builder-grade
$266/sq ft
$186,000
Midrange
$361/sq ft
$253,000
High-end / custom
$494/sq ft
$346,000
Based on 700 sq ft, a typical size for a detached accessory dwelling unit. Your size and scope change the total — run your own numbers.
What goes into a adu / guest house estimate
- •Site work, foundation & structure — the parts you never see but pay for first
- •Framing, roofing & the weather-tight shell
- •Mechanical, electrical & plumbing systems
- •Interior finishes — the single biggest swing in the whole budget
- •Permits, plan review & local fees
- •General conditions, contractor overhead & contingency
Get your exact Phoenix, AZ estimate
Line-by-line costs for your specific project + a builder-ready brief. Free — no account, no card to see your number.
Estimate my adu / guest house →Phoenix, AZ adu / guest house cost — FAQ
How much does it cost to build an ADU in Phoenix, AZ?
A typical a detached accessory dwelling unit in Phoenix, AZ runs about $186,000 to $346,000 — roughly $266–$494 per square foot across 700 sq ft. Phoenix, AZ indexes at ×0.95 versus the national building-cost average — a city-level match in our cost index.
What is the cost per square foot to build an ADU in Phoenix, AZ?
Expect about $266/sq ft at a starter finish level, $361/sq ft midrange, and $494/sq ft for high-end custom work. Your exact rate depends on finish level, site conditions, and design complexity.
What drives the price up or down?
Finish level is the biggest lever, followed by site and access, structural complexity, and (for a remodel or addition) how much of the existing structure you keep. Local permit fees and labor availability move the total as well.
How do I get an exact estimate for my project?
Answer a few questions about your project and get a free, itemized estimate — line by line, with a builder-ready brief — in a few minutes. No account or payment required to see your number.
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ADU / guest house costs in other cities
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Estimates are engine-generated planning figures for Phoenix, AZ, not a quote. Actual pricing depends on your design, site, and builder. All cost guides.