What HB 2720 Is and When It Started
HB 2720 is a state law about accessory dwelling units, or ADUs. An ADU is a smaller, second home on the same lot as your house. It has its own place to sleep and its own bathroom, and it can have its own kitchen.
The governor signed the bill on May 21, 2024. It took effect on September 14, 2024, and cities had until January 1, 2025 to update their rules.
If a city missed that date, the law says ADUs are allowed on every home lot in that city, with no limits.
You may know ADUs as casitas, guest houses or in-law suites. The law treats them all the same. One rule holds for every one: the main house has to be bigger than the ADU.
Which Phoenix Valley Cities the Law Covers
The law applies to cities and towns with more than 75,000 people. State law counts people with the latest U.S. census, which is the 2020 census.
| City or town | Does HB 2720 apply? |
|---|---|
| Phoenix | Yes |
| Scottsdale | Yes |
| Mesa | Yes |
| Gilbert | Yes |
| Chandler | Yes |
| Tempe | Yes |
| Queen Creek | No. Under 75,000 at the 2020 census, so town rules apply. |
| Fountain Hills | No. Town rules apply. |
| Paradise Valley | No. Town rules apply. |
| San Tan Valley | Ask the town. It became a town in September 2025, after the last census. |
Some lots are left out even in covered cities. The law doesn't apply on tribal land, near a military airport, or near some public airports where noise runs over 65 decibels. If you live near an airport, ask your city whether your lot sits in one of these zones.
How Many ADUs You Can Build
If your city is covered, it must allow at least one attached and one detached ADU. That goes for any lot where a house is allowed.
Attached means it shares a wall with your house. Detached means it stands on its own, like a backyard casita.
Lots of one acre or more can get one more detached ADU. The catch: at least one ADU on the lot has to be rented as affordable housing, to households earning up to 80% of the area's median income. That's set by a deed restriction or an agreement with the city.
These are floors, not ceilings. Your city can allow more. Phoenix, for one, says a third ADU may be allowed in some cases.
The city also has to treat an ADU as a permitted use. That means no public hearing, variance or special permit just to build one. You still go through plan review and building permits.
How Big Your ADU Can Be
Your city must allow an ADU of at least 75% of the main home's floor area or 1,000 square feet, whichever is less. Floor area means the inside living space. Here's how that works out:
| Main home's living space | Size your city must allow, at least |
|---|---|
| 1,200 sq ft | 900 sq ft |
| 1,600 sq ft | 1,000 sq ft |
| 2,400 sq ft | 1,000 sq ft |
Cities can allow bigger units. Phoenix lets each ADU reach 75% of the main home, capped at 1,000 square feet on lots up to 10,000 square feet. On bigger lots, the cap is 3,000 square feet.
Lot coverage still counts. Each zone limits how much of the lot buildings can cover, so a big ADU on a small lot may not fit.
What Cities Can't Require
In a covered city, the law limits what your city can ask of an ADU:
- No extra parking, and no fee in place of parking
- No rear or side setbacks of more than 5 feet from the property line
- No height, setback, lot size or coverage rules stricter than those for a house in the same zone
- No need to match your home's exterior design, roof pitch or finish materials
- No family, marriage, job or other tie needed between you and the person who lives in the ADU
- No street upgrades, unless your build damages the street
- No commercial building code and no fire sprinklers
- No deed covenant about the ADU as a condition of the permit
The law doesn't say whether a city can make you live on the lot when you rent the ADU long-term. Ask your city about owner-occupancy rules before you plan.
Renting Out Your ADU
Cities can't stop you from renting the ADU, or the main house, as a long-term rental. They can't stop you from advertising it, either. Long-term means a lease of 90 days or more, or month to month.
Short-term rentals, like Airbnb, fall under a separate state law. Cities can't ban them outright, but they can add rules such as permits and an emergency contact.
One rule matters for new ADUs. Say your ADU got its final city okay on or after September 14, 2024. Then your city can make you live on the property to rent short-term there.
What Still Applies to Your Build
HB 2720 limits what cities can require. It doesn't clear every rule:
- HOA rules. The law doesn't cancel private CC&Rs, so if your HOA limits casitas or guest houses, those limits can still apply.
- Building, fire and health codes. Your ADU still has to meet them, apart from the sprinkler and commercial code rules above.
- Permits and inspections. Your city still reviews the plans and inspects the work.
- Utility easements. You can't build on a public utility easement without written consent from the utilities that use it or may use it.
What This Means for Your Lot
Before you sketch a floor plan, check five things:
- Your city or town, using the table above
- Your lot size and your home's living space, both listed on your county assessor's website
- Your HOA's CC&Rs, for rules on guest houses or accessory buildings
- Any utility easements on your plat or survey
- Whether your lot sits in an airport zone
Tight backyard? A garage conversion uses the slab, walls and roof you already have. Turning it into a bedroom or an in-law suite is often a quicker way to add living space.
How Masizo Helps You Build an ADU
We're a licensed builder in Gilbert, AZ ROC #336058. We build casitas, guest houses, in-law suites and garage conversions all over the Valley. We've built a casita and turned two garages into a bedroom and a suite.
It starts with a free consultation. We look at your lot and your HOA rules, then talk through what you want to build. You get a clear quote with no obligation.
Then we handle the permits and zoning with your city. We build the unit and schedule the city inspections.
