Casitas, detached or attached guest suites, are a long Arizona tradition and are increasingly built as ADUs for family members or rental income. A 2024 state law (HB 2720) requires larger Arizona cities to allow accessory dwelling units on single-family lots. Each city still sets its own size, height, setback and design rules, and HOA rules can be stricter than city code.
What room additions & casitas typically costs in Phoenix
| Scope | Typical range (estimate) | What that usually covers |
|---|---|---|
| Basic room (400 sq ft) | $97,000 – $155,000 | bedroom/family room, simple roofline |
| With bath or kitchenette (400 sq ft) | $136,000 – $194,000 | adds plumbing |
| Second story / high-end (400 sq ft) | $194,000 – $291,000 | structural work, premium finishes |
| Detached casita (400 sq ft, with bath) | $147,500 – $233,000 | Foundation, utilities trenching, bath, mini-split; site work varies |
Planning estimates for typical projects, not quotes. Your bids will depend on size, condition, materials and permit requirements.
Permits and plans
Room additions always need a permit and plans in Phoenix, and site plans must show setbacks to property lines. Expect plan review, then inspections at footing, framing, rough plumbing and electrical, insulation and final. In Scottsdale, Paradise Valley-adjacent and hillside lots, check for hillside or Environmentally Sensitive Lands rules before designing.
Utility and site costs people forget
- Trenching water, sewer and power to a detached casita, which can be expensive on caliche lots or long runs
- Electrical panel upgrades for a new mini-split or kitchenette
- Matching roof tile and stucco texture so the addition doesn't look tacked on
Phoenix project cost estimator
Planning estimate
$135,800 – $194,000
Rough planning range only — not a quote. Real bids depend on site conditions, permits, materials and the contractor.
Room Additions & Casitas: common questions
Can I rent out a casita in Phoenix?
Many cities now allow ADUs to be rented, but rules on owner occupancy, short-term rentals and parking vary by city and HOA. Check both before you build.
Where we match room additions & casitas projects
Phoenix · Scottsdale · Mesa · Chandler · Gilbert · Tempe · Glendale · Peoria · Surprise & Sun City · Goodyear & West Valley