As of January 1, 2026, the Arizona casita law is fully in effect — not just in big cities, but across unincorporated Maricopa County too. If you’ve been holding off on building a backyard ADU because you weren’t sure what your city or county would allow, that uncertainty is mostly gone. Here’s what changed and what it means for you.
What is the Arizona Casita Law?
“Casita Bill” refers to two Arizona laws passed back to back:
- HB 2720 (signed May 2024, effective January 1, 2025) required every Arizona city with a population over 75,000 — including Phoenix, Scottsdale, Mesa, Chandler, Gilbert, and Tempe — to allow at least one attached and one detached accessory dwelling unit (ADU) on any single-family lot.
- HB 2928 (signed May 2025, effective January 1, 2026) extended nearly identical rules to counties, closing the gap for homeowners in unincorporated areas and smaller communities that HB 2720 didn’t cover.
Together, they rewrote how ADUs — also called casitas, guest houses, or granny flats — get approved in Arizona.
What changed for Maricopa County homeowners
HB 2928 required counties to allow ADUs by January 1, 2026. A county that hadn’t adopted its own rules by then must allow ADUs on all residential lots without limits. Under the new rules, if you own a single-family lot in unincorporated Maricopa County, the county must allow:
- At least one attached ADU and one detached ADU on your lot
- An additional affordable unit on parcels of one acre or more
- ADUs of at least 75% of the primary home’s floor area or 1,000 square feet, whichever is less (a county may allow larger).
The law also removed several common roadblocks:
- No family occupancy requirement. You’re no longer required to have a relative live in the unit — you can rent it to anyone.
- No extra parking mandates in most areas.
- No forced design matching. Cities and counties can no longer require your ADU’s exterior materials or roofline to match your main house.
- No special use permits or public hearings. If your ADU meets the minimum standards, approval is by right — not discretionary.
Wondering what fits in that footprint? Browse our casita designs.
What hasn’t changed — your HOA still has the final say
This is the part most homeowners miss: neither HB 2720 nor HB 2928 overrides your HOA’s CC&Rs. State law and your HOA’s covenants operate as two separate systems. You can get full sign-off from Maricopa County’s planning department and still be violating your HOA’s rules the moment you break ground.
If your community has an HOA, check your recorded covenants before you plan anything — that’s a conversation worth having early, not after you’ve paid for design work.
FAQ
Yes. HB 2928 required counties to allow ADUs by January 1, 2026. A county that hadn’t adopted its own rules by then must allow ADUs on all residential lots without limits.
Yes. The old family-occupancy requirement was removed. You can rent your ADU long-term to anyone you choose.
No. HB 2720 and HB 2928 both preserve HOA covenants. If your HOA’s CC&Rs prohibit detached structures or additional dwelling units, that restriction still applies regardless of what the county allows.
Under HB 2928, a county must allow an ADU of at least 75% of your main home’s floor area or 1,000 square feet, whichever is less. A county may allow larger. Confirm the limit for your parcel with the county.
No. If your ADU meets the state’s minimum standards, the county must approve it — approval is no longer discretionary.
Ready to build your casita?
Maricopa Casitas has been tracking these changes closely and knows exactly what Maricopa County requires under the new ordinance. Contact us for a consultation on what’s possible on your lot.
Before you reach out, see what a casita costs to build in Maricopa County and browse our completed builds.