Phoenix ADU, casita, and guest house cost — from permit data, not guesses.
Whether you call it an ADU, a casita, or a guest house addition, it's the same building project — and Phoenix homeowners are doing it more than ever. We'll show you what it actually costs in your zip, whether your lot qualifies, and how to finance it without giving up your current mortgage rate.
What you're actually paying for.
ADU pricing in Phoenix breaks into three common shapes. Numbers below are calibrated against the Maricopa permit dataset and our cost engine — the same numbers your contractor will quote inside a Statement of Work.
| Type | Cost / sqft | Example |
|---|
| Detached ADU / casita | $350/sqft | 700 sqft → ≈ $245K |
| Guest house addition (attached) | $300–$350/sqft | 500 sqft → ≈ $150–$175K |
| Garage conversion | $150–$200/sqft | 400 sqft → ≈ $60–$80K |
From "what if" to keys, in one platform.
Most ADU projects break down because the homeowner has to coordinate an architect, a contractor, a lender, and the city separately. We do all four under one Statement of Work.
- Reality Check — enter your zip, see real cost ranges, projected post-build value, and a financing path in 60 seconds, free.
- Permit-ready plans, included in your project at cost — custom floor plans, 3D renders, full trade takeoffs, and an Arizona architect’s stamp where required.
- Vetted contractor + ARV financing — a scope-locked, pre-funded project, financed on after-repair value so your low first-mortgage rate stays untouched.
- Milestone-verified construction — geo-tagged photo and video draws replace the in-person bank inspector.
Frequently Asked Questions
What is an ADU, and how is it different from a casita or guest house?
An ADU — Accessory Dwelling Unit — is a self-contained second home on the same lot as your main house. In Phoenix vernacular, a casita and a guest house are the same thing. Whether someone calls it an ADU, a casita, or a guest house addition, the building department treats it the same way.
How much does it cost to build an ADU in Phoenix?
For a fully detached, livable ADU in the Phoenix metro, expect roughly $350/sqft of finished space — so a 700 sqft casita lands around $245,000. Garage conversions run lower (around $150–$200/sqft) because the shell already exists. Calibrated against real Maricopa permits and Arcadia/85018 market data.
Is my Phoenix lot eligible for an ADU?
Most single-family lots over 6,000 sqft in our service zips qualify under current Phoenix and Scottsdale zoning. Specific setbacks, height limits, and parking requirements depend on your municipality and HOA.
Can I finance an ADU build with my existing mortgage?
Yes — and you don't have to give up your low-rate first mortgage. Most homeowners finance ADUs with a second-lien construction loan underwritten on the after-repair value of the property. ExpandEase originates these loans through our bank partners and handles the draw schedule, contractor verification, and inspections.
How long does an ADU project take from idea to move-in?
Plan on 3–4 weeks for design and stamped plans, 4–8 weeks for permitting depending on the city, and 4–6 months for construction — roughly 6–9 months total for a standard ADU in Phoenix or Scottsdale.