Everything homeowners ask about building an ADU in Tempe — answered with 2026 data.
Yes, ADUs are allowed in All single-family residential districts citywide (per ARS 9-461.18 and Tempe's amended ADU ordinance) in Tempe, AZ. The maximum size for a detached ADU is 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less. Attached ADUs can be up to 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less. Tempe has an ADU-friendliness score of 7/10. Check our full Tempe ADU rules page for complete zoning details.
ADU construction in Tempe typically costs $120,000-$250,000. The cost per square foot averages $140-$280. Garage conversions are more affordable at $60,000-$140,000, while prefab ADUs cost $85,000-$200,000. Permit fees add Building permit and plan review fees based on valuation — Confirm with Tempe Community Development to your budget. See our detailed Tempe ADU cost guide.
Detached ADUs in Tempe can be up to 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less. Attached ADUs are limited to 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less. Junior ADUs (JADUs) have a cap of Not a category in Arizona (no JADU designation). Maximum height is Same as the underlying zoning district standard (typically 30 ft); no stricter ADU-specific cap allowed. You are allowed up to 2 per lot (1 attached + 1 detached); a 3rd detached ADU allowed on lots 1+ acre if one unit is restricted-affordable on a qualifying lot.
Rear setback: 5 feet minimum (all districts, unless the district allows less). Side setback: 5 feet minimum, including street side yards (all districts, unless the district allows less). Front setback: Per underlying zoning district — Confirm with Tempe Community Development. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
No additional parking may be required (ARS 9-461.18 bars ADU parking mandates and in-lieu fees). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for long-term rentals; owner must reside on site only if an ADU built on/after Dec 20, 2024 is licensed as a short-term rental. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Tempe is typically Typically 4-8 weeks for residential plan review — Confirm with Tempe Community Development. Plan check: 2-4 weeks typical — Confirm with Tempe Community Development. Pre-approved plans availability: No city pre-approved plan library — Confirm with Tempe Community Development.
Average ADU rental income in Tempe: 1-bedroom units rent for $1,300-$1,700/month, 2-bedroom units for $1,600-$2,100/month. Short-term rentals: Allowed with an Arizona/Tempe STR license, but the owner must live on site if the ADU was built on/after Dec 20, 2024. Expected ROI: 7-10% annual return.
The minimum lot size for an ADU in Tempe is No ADU-specific minimum — allowed on any lot with a permitted single-family dwelling. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Tempe, a garage conversion typically costs $60,000-$140,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.