Mesa & Tempe, Arizona
Find out what you can legally build in your backyard.
Arizona law now entitles you to a casita on almost any single-family lot — no public hearing, no variance, no extra parking. Enter your address and we will tell you how big, how close to the fence, and where it fits, with the statute cited line by line.
- Maximum size
- 1,000 sq ft
- or 75% of your house, whichever is less
- Side and rear setback
- 5 ft or less
- a ceiling the city cannot exceed
- Parking required
- None
- and no fee in place of it
What the report tells you
The arithmetic, not just the answer
We show the calculation: your house's interior area, 75% of it, the 1,000 square foot ceiling, and which one binds. If a number looks wrong you can see exactly where it came from.
Which rule is actually stopping you
Most reports quote the statutory maximum. Often the real limit is your district's lot coverage cap, or simply the shape of the lot once setbacks come off. We tell you which, because that is the thing you can do something about.
A scale drawing of your lot
We take the county parcel boundary, inset it by the setbacks that apply to your district, subtract your existing buildings where we have the data, and find the largest rectangle that fits — measured square to your lot lines, not to compass north.
The two things that catch people out
Public utility easements usually run along the rear and side lot lines, exactly where a detached unit wants to go, and you cannot build over one without written utility consent. And your HOA's covenants still bind you — the statute only constrains cities.
Your unit number asked up front
If your address covers several separately assessed units, we ask which one is yours before running anything, not after. A condo and the building next door have different lot sizes and different answers.
What we could not verify
Every report ends with a list of the things we could not confirm. Where we do not know, we say so rather than printing a confident number — the whole point is that you can act on this.
Pick your city
The state statute sets a floor that both cities have to meet, but Mesa and Tempe implement it differently — and in a few places one is noticeably more generous.
Mesa, Arizona
517,142 residents · Mesa Zoning Ordinance § 11-31-3
- No minimum lot size to establish a unit
- An existing house qualifies the lot whatever the zoning
- Converting an existing shed keeps its current setbacks
- No manufactured homes, RVs or trailers
Read the Mesa rules →
Tempe, Arizona
190,113 residents · Tempe Zoning and Development Code § 3-402
- Up to 2,000 sq ft on lots of an acre or more
- No design review and no development plan review
- Tiny homes and modular construction allowed
- Three-bedroom cap on units under 1,000 sq ft
Read the Tempe rules →
Common questions
Can I build a casita in my backyard in Mesa or Tempe?
Almost certainly yes. Arizona law requires every city over 75,000 people, including Mesa and Tempe, to allow at least one attached and one detached accessory dwelling unit on any lot where a single-family dwelling is allowed, as a permitted use. That means no public hearing, no variance and no conditional use permit. The exceptions are tribal land, land near a military airport, and land where airport noise exceeds 65 decibels.
How big can an ADU be in Arizona?
Seventy-five percent of the interior habitable area of your house, or 1,000 square feet, whichever is smaller. A 1,600 square foot house gives you 1,000 square feet; a 1,000 square foot house gives you 750. Tempe allows up to 2,000 square feet on lots of an acre or more, which is more generous than the state minimum.
Do I have to live on the property to rent out a casita?
No. Arizona law forbids a city from requiring any family, marital, employment or other pre-existing relationship between the occupants of the two dwellings, and forbids prohibiting either dwelling from being leased as separate long-term rental housing. An owner-occupancy requirement is not available to the city. A private HOA covenant is a different matter and may still restrict you.
Do I need extra parking for an ADU?
No. A city may not require additional parking for an accessory dwelling unit, and may not charge a fee instead of parking. In Mesa, if you convert a garage into a unit you do not have to replace the covered parking elsewhere on the lot.
How close to the fence can I build a casita?
A city may not require more than five feet from the side or rear property line. It also may not hold an accessory unit to a stricter standard than a house in the same zoning district, so where a district already allows a house closer than five feet, the unit gets that narrower setback too. Front setbacks are not capped and follow the district standard.
Is this free?
The report is free and you do not need an account or an email address to see it. The plan is to make money by passing homeowners who want quotes to local ADU builders, and only if you ask us to — but that part is not built yet, so right now there is nothing to sell you and nothing we collect.
Where this comes from