Everything homeowners ask about building an ADU in Mesa — answered with 2026 data.
Yes, ADUs are allowed in Any lot in a district where a single residence is allowed: Agricultural (AG), Single Residence (RS), Small Lot Single Residence (RSL), Multiple Residence (RM), Downtown Residence (DR), Mixed Use (MX) and the NC, LC and GC commercial districts; a lot in any other district qualifies if its principal use is an existing single residence (MZO 11-31-3(A), Ord. 6025). Historic Districts need a Certificate of Appropriateness (Ch. 74); ARS 9-461.18(G) excludes tribal land and airport-noise areas. in Mesa, AZ. The maximum size for a detached ADU is 75% of the primary residence's interior habitable area or 1,000 sq ft, whichever is less (11-31-3(C)); a 1,200 sq ft house allows up to 900 sq ft, a house of 1,334 sq ft or more allows the full 1,000. Since Ord. 5950 (Aug 2025) the ADU no longer counts toward the cap on combined detached accessory floor area in 11-30-17(A)(4). District lot-coverage and building-coverage limits still apply (11-31-3(E)). Attached ADUs can be up to Same cap as detached: 75% of the primary residence's interior habitable area or 1,000 sq ft, whichever is less. Mesa has an ADU-friendliness score of 7/10. Check our full Mesa ADU rules page for complete zoning details.
ADU construction in Mesa typically costs $150,000-$280,000. The cost per square foot averages $175-$350. Garage conversions are more affordable at $80,000-$150,000, while prefab ADUs cost $150,000-$300,000. Permit fees add Valuation-based (Development Services Schedule of Fees, July 2026): $500 plus $6 per $1,000 of valuation over $25,000, up to $200,000; then $1,550 plus $9 per $1,000. A $150,000 ADU pays about $1,250 and a $250,000 unit about $2,000, plan review and trade permits included. to your budget. See our detailed Mesa ADU cost guide.
Detached ADUs in Mesa can be up to 75% of the primary residence's interior habitable area or 1,000 sq ft, whichever is less. Attached ADUs are limited to Same cap as detached: 75% of the primary residence's interior habitable area or 1,000 sq ft, whichever is less. Junior ADUs (JADUs) have a cap of Mesa has no junior ADU category. A unit carved out of the existing house is simply an attached ADU: same 75%/1,000 sq ft cap, a separate outside entrance with no internal door to the house (Ord. 6025), no more than one kitchen, and no added setbacks for an internal renovation (11-31-3(B)-(D)). Maximum height is Same as the primary residence height limit for the underlying zoning district (11-31-3(F)); the city's ADU page confirms a two-story ADU is allowed wherever the district allows a two-story house. Unlike an ordinary detached accessory building over 15 ft (11-30-17(B)(2)(e)), an ADU keeps its 5-ft side and rear setbacks at any permitted height. You are allowed up to One attached plus one detached ADU per lot on a qualifying lot.
Rear setback: 5 ft minimum for a new attached or detached ADU (11-31-3(D)(1)(a), as rewritten by Ord. 5950, effective Aug 2025). An existing detached building that meets the 11-30-17 accessory-building setbacks, or is legal non-conforming, can be converted to an ADU with no added setback; an expansion may follow the existing non-conforming line if it does not worsen it. Since Ord. 6025 a detached ADU must also sit at least 5 ft from the house, other ADUs and accessory buildings. Side setback: 5 ft minimum on interior side lines for new construction, with the same conversion exceptions as the rear setback (11-31-3(D)); a corner-lot street side follows the primary residence's street-side setback for the district (D)(1)(b). Uninhabitable space attached to an ADU (garage, storage, workshop) follows the district setbacks for an attached ADU, or the 11-30-17 accessory-building setbacks for a detached ADU (Ord. 6025). Front setback: Same as the primary residence's front and secondary-front (street-side) setback for the underlying district (11-31-3(D)(1)(b)). An internal renovation of the house needs no new setbacks; a ground-floor addition for an ADU must meet the 5-ft side/rear rule, and a second-story addition must meet the house's own district setbacks (11-31-3(D)(3), Ord. 5950). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None. No additional parking spaces are required for an ADU, and a garage or carport converted to an ADU need not have its covered parking replaced elsewhere on the lot (11-31-3(G)); ARS 9-461.18(B)(3) bars parking requirements and in-lieu fees. The city's ADU page notes the primary residence must still keep its own two required spaces. 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. Neither 11-31-3 nor state law requires the owner to live on site, and ARS 9-461.18(B)(2) bars any family, marital or employment relationship test between the house and ADU occupants. The ADU may be leased separately long-term (ARS 9-461.18(B)(1)) but may not be sold separately from the primary residence (city ADU page). 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 Mesa is typically Written plan-review comments or approval within 10 working days (Monday-Thursday, excluding holidays) per Mesa's Residential Construction page; an expedited 5-working-day review costs an extra 100% of the permit fee. Allow for at least one re-submittal cycle. Plan check: Full residential plan review within the 10-working-day target; a non-refundable $500 application deposit (valuations $25,000-$200,000) is credited to the permit fee. Fourth and later re-submittals before issuance cost $120 per staff hour (2-hour minimum) and post-permit addenda $120 per hour with a $120 deposit. Plans are checked against the 2024 IRC and companion codes with Mesa amendments and the 2023 NEC; state law bars a fire-sprinkler or commercial-code requirement for an ADU (ARS 9-461.18(D)). Pre-approved plans availability: Mesa's Preapproved Housing Design Plan Program (per the city, under ARS 9-461.19; the plan classes match ARS 9-461.20) accepts Class 4 ADU plans of exactly 200, 600 or 1,000 sq ft, with no review fee and standard permit fees at issuance; users sign a plan agreement and may need site-specific sheets. As of September 2026 the program page lists the classes but posts no ADU plans to choose from, so email PermitServices@mesaaz.gov for what is available; state law required at least three ADU plans from July 1, 2026.
Average ADU rental income in Mesa: 1-bedroom units rent for $1,250-$1,500/month, 2-bedroom units for $1,500-$1,750/month. Short-term rentals: Yes, with a Mesa Short-Term Rental License (City Code 5-15, in force since February 1, 2023): $250 application and $250 annual renewal per unit, issued only to the deeded owner, with an Arizona TPT licence, an emergency . Expected ROI: 6-11% gross rental yield (a $150,000-$280,000 detached build at $1,300-$1,700/mo, before taxes, vacancy, insurance and financing).
The minimum lot size for an ADU in Mesa is None. 11-31-3(B)(1): 'There are no minimum lot size requirements to establish an ADU.' The unit must still fit within the district's lot-coverage and building-coverage limits (11-31-3(E)), and a third ADU is possible only on lots of 1 acre or more. 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 Mesa, a garage conversion typically costs $80,000-$150,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
Tell us about your project and we'll pass it to ADU builders serving Mesa. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.