Accessory dwelling units in Tempe, Arizona
Tempe is small, built out and expensive, which makes it one of the places in the valley where an accessory dwelling unit makes the most financial sense. At around 190,000 residents it is well over the 75,000 threshold in A.R.S. § 9-461.18, and Ordinance No. O2024.51, adopted in November 2024, brought the city’s ADU section into line with the statute.
Tempe went further than it had to in three places. It allows up to 2,000 square feet on lots of an acre or more, where the state floor is 1,000. It exempts accessory units from its building design, parking, landscape, lighting and development plan review chapters outright — removing the slowest parts of the city process. And it wrote a supremacy clause into its own ordinance: where § 3-402 conflicts with the state statute, the statute controls.
Tempe also publishes its dimensional standards as queryable attributes on its own zoning layer, which means the setbacks, heights and coverage figures in our reports for Tempe addresses are read live from the city rather than typed in by us.
The numbers, in short
A.R.S. § 9-461.18Maximum size
1,000 sq ft
Or 75% of your house’s interior habitable area, whichever is less. On lots of an acre or more Tempe raises the ceiling to 2,000 sq ft.
Side and rear setback
5 ft or less
Five feet is the most a city may require — and where a district lets a house sit closer, your unit gets the narrower figure too.
Parking
None
No additional spaces, and no fee charged in place of them.
Units permitted
1 attached + 1 detached
A second detached unit becomes available on a lot of an acre or more if one unit is deed-restricted as affordable.
Setbacks by Tempe zoning district
City of Tempe Zoning District feature layer; Tempe ZDC § 4-202The left-hand columns are what Tempe requires of a house. The right-hand columns are what an accessory unit is entitled to once A.R.S. § 9-461.18(B)(5) and (B)(6) are applied. Where the two differ at the side or rear, the statutory cap is doing the work.
| District | Min lot | House front | House side | House rear | Unit side | Unit rear | Height | Coverage |
|---|---|---|---|---|---|---|---|---|
| R1-15 | 15,000 sq ft | 35 ft | 15 ft | 30 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-10 | 10,000 sq ft | 30 ft | 10 ft | 25 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-8 | 8,000 sq ft | 20 ft | 7 ft | 20 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-7 | 7,000 sq ft | 20 ft | 7 ft | 15 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-6 | 6,000 sq ft | 20 ft | 5 ft | 15 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-PAD | 6,000 sq ft | 20 ft | 5 ft | 15 ft | 5 ft | 5 ft | 30 ft | 45% |
| R1-5 | 5,000 sq ft | 20 ft | 5 ft | 15 ft | 5 ft | 5 ft | 30 ft | — |
| R-2 | 3,600 sq ft | 20 ft | 10 ft | 15 ft | 5 ft | 5 ft | 30 ft | 45% |
| R-3R | 2,900 sq ft | 20 ft | 10 ft | 15 ft | 5 ft | 5 ft | 30 ft | 45% |
| R-3 | 2,180 sq ft | 20 ft | 10 ft | 15 ft | 5 ft | 5 ft | 30 ft | 50% |
| R-4 | 1,740 sq ft | 20 ft | 10 ft | 10 ft | 5 ft | 5 ft | 40 ft | 60% |
| R1-4 | — | — | 5 ft | 15 ft | 5 ft | 5 ft | 35 ft | — |
| RO | — | 15 ft | 10 ft | 10 ft | 5 ft | 5 ft | 30 ft | 35% |
| RMH | — | — | — | — | — | — | — | — |
- City ordinanceCity of Tempe Zoning District feature layer; Tempe ZDC § 4-202 (read 2026-10-10)
- City GISCity of Tempe — Zoning District feature layer (cached copy) — The live layer was unreachable, so these figures come from our 2026-10-10 copy of it. (read 2026-10-10)
- City GISCity of Tempe — Zoning District feature layer (cached copy) — The live layer was unreachable, so these figures come from our 2026-10-10 copy of it. (read 2026-10-10)
- City GISCity of Tempe — Zoning District feature layer (cached copy) — The live layer was unreachable, so these figures come from our 2026-10-10 copy of it. (read 2026-10-10)
Gaps in this table
- R1-5: Tempe's zoning layer does not publish a maximum coverage for R1-5, so we cannot compute a coverage budget for this lot.
- R1-4: Tempe's zoning layer does not publish a front setback for R1-4. The governing figure is in the district setback table at Tempe ZDC § 4-202 and we have not encoded it, so we cannot state your front setback.
- RMH: Tempe's zoning layer does not publish a front setback for RMH. The governing figure is in the district setback table at Tempe ZDC § 4-202 and we have not encoded it, so we cannot state your front setback.
What is distinctive about Tempe
Tempe Zoning and Development Code § 3-402- Up to 2,000 sq ft on an acre
- On lots of an acre or more Tempe doubles the state cap, still subject to the 75%-of-the-house rule. If your lot is near an acre, the exact size is worth confirming.
- No design review, no development plan review
- Accessory units are expressly excluded from Tempe’s multi-family building design, parking, landscape and wall, lighting, and development plan review chapters.
- State law wins on conflict
- Tempe’s ordinance says that where it conflicts with A.R.S. § 9-461.18, the state law controls. Useful if a reviewer applies a stricter reading.
- Tiny homes and modular allowed
- Tempe permits tiny-home, prefabricated and modular construction on a permanent foundation, and even a trailer-built unit once the axles come off and the chassis is fixed down.
- Three bedrooms maximum under 1,000 sq ft
- A unit limited to 1,000 square feet may have no more than three bedrooms. On lots of an acre or more there is no bedroom cap.
- Existing guest quarters count against you
- A permitted guest house already uses up your one detached unit — but converting it to a rentable unit may exceed the normal size cap and terminates any rental-restriction covenant on it.
Tempe Zoning and Development Code § 3-402 — Accessory Dwelling Units. Brought into line with state law by Ord. No. O2024.51, adopted 21 November 2024. Read the ordinance.
Questions Tempe homeowners ask
Can I build a casita in Tempe?
Yes. Tempe permits one attached and one detached accessory dwelling unit on any lot in a residential district that contains a single-family dwelling. The property keeps its single-family status, and the unit is a permitted use — no public hearing, no variance, no conditional use permit, and no development plan review.
How big can a casita be in Tempe?
On a lot under an acre, 1,000 square feet of interior habitable area or 75% of the main residence’s gross floor area, whichever is less. On a lot of an acre or more, 2,000 square feet or 75%, whichever is less. Garages, carports and exterior storage do not count toward gross floor area.
How close to the property line can I build a casita in Tempe?
Five feet from the rear, side and street-side property lines in every district, unless the district or an overlay allows less — in which case the narrower figure applies. The front setback follows the district table: 20 feet in R1-5 through R1-8, 30 feet in R1-10, 35 feet in R1-15. Where the lot abuts a public alley, the rear and side setbacks are measured from the midpoint of the alley.
Do I need a permit to build a casita in Tempe?
You need building permits and your utility connections have to meet city standards, but you do not need a zoning hearing, a variance or development plan review. Tempe excludes accessory units from § 6-306 development plan review and from its building design, parking, landscape and lighting chapters.
Can I rent out a casita in Tempe?
Yes — an accessory unit in Tempe is designed to be rented or leased independently of the main residence. Short-term and vacation rental is permitted subject to Tempe City Code Chapter 16a, Article X, which carries its own requirements. The unit may not be subdivided or sold separately from the lot.
How many bedrooms can a Tempe casita have?
Up to three, if the unit is limited to 1,000 square feet of interior habitable area. On lots of an acre or more there is no restriction on the number of bedrooms. Mesa imposes no bedroom cap at all.
Do I need extra parking for a Tempe casita?
No additional parking is required for the unit. If the unit removes or modifies a parking space that was required for the main residence, that space has to be replaced somewhere the Community Development Director approves.
Can I put a tiny home in my backyard in Tempe?
Yes, on a permanent foundation and compliant with Tempe’s adopted tiny-home building code. Tempe also allows prefabricated and modular units, and units built on a trailer once the suspension and axles are removed and the chassis is permanently attached to a foundation. Mesa prohibits all of these.
What if I already have a guest house in Tempe?
An existing permitted guest quarters counts toward your one detached unit, so you would not get an additional detached unit on top of it. You may convert the guest quarters into a rentable accessory unit, and in that case the interior area may exceed the normal cap. The conversion also terminates any rental-restriction covenant on the guest quarters.
What zoning districts allow casitas in Tempe?
All residential districts identified in Tempe ZDC § 2-102, where the property contains a single-family dwelling. That includes the single-family R1 districts, the multi-family R-2, R-3, R-3R and R-4 districts, R1-PAD and the Residential/Office district.
The full Tempe rules
Every provision, subsection by subsection: size, setbacks, height, coverage, parking, permits, rental, easements and covenants.
Read the explainer →
Compare with Mesa
The state floor is the same in both cities, but the implementations differ — on size, on construction type, and on what counts against your allowance.
Mesa rules →
Statute text read from A.R.S. § 9-461.18 on azleg.gov. Tempe population 190,113, per the U.S. Census Bureau — comfortably over the 75,000 threshold at A.R.S. § 9-461.18(H).