Everything homeowners ask about building an ADU in Avondale — answered with 2026 data.
Yes, ADUs are allowed in Permitted with conditions (PC) in AG, RR-43, RR-18, R1-35, R1-15, R1-10, R1-8, R1-7, R1-6 and R1-5, and in R-2, R-3 and MH; prohibited in R-4 (§28-32 matrices). Only where the district allows a single-family home, never on a lot with a duplex, townhome or multi-family development (§28-33(a)(3)(B)). Excluded: tribal land and land in the vicinity of a military, FAA-licensed, general aviation or public airport (§28-33(a)(12)) — Luke AFB and Phoenix Goodyear Airport are nearby; get a parcel check in Avondale, AZ. The maximum size for a detached ADU is The lesser of 75% of the gross floor area of the existing single-family dwelling or 1,000 sq ft (§28-33(a)(3)(A)); for this section gross floor area means the interior habitable area of the house or the ADU (§28-33(a)(3)(A)(I)), not the exterior-wall measure in §28-15. No more than two bedrooms (§28-33(a)(3)(G)). A detached ADU counts toward the district building coverage cap: 45% in R1-8 to R1-5, 40% R1-10, 20% R1-15, 30% RR-18, 15% AG/RR-43/R1-35 (§28-33(a)(3)(E); §28-35.A; §28-133(f)). Attached ADUs can be up to Same cap — the lesser of 75% of the house's interior habitable area or 1,000 sq ft, and no more than two bedrooms. Avondale has an ADU-friendliness score of 6/10. Check our full Avondale ADU rules page for complete zoning details.
ADU construction in Avondale 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 FY2027 schedule (eff. 9/1/2026): permit $1,247 + $8 per $1,000 of valuation over $100,000, plan review 65% of that, $102 application fee, $158 C of O — about $2,400 for a 600 sq ft casita valued near $106,000 and $3,320 at 1,000 sq ft (~$176,000). Impact fees are separate to your budget. See our detailed Avondale ADU cost guide.
Detached ADUs in Avondale can be up to The lesser of 75% of the gross floor area of the existing single-family dwelling or 1,000 sq ft. Attached ADUs are limited to Same cap — the lesser of 75% of the house's interior habitable area or 1,000 sq ft, and no more than two bedrooms. Junior ADUs (JADUs) have a cap of Not a category in Arizona — Avondale's Zoning Ordinance has no junior ADU designation (§28-15 definitions and §28-32 matrices list only 'Accessory dwelling unit (ADU)', read 9/20/2026). New guest houses are no longer a permitted use; an existing permitted guest house begun before November 18, 2024 counts as one of your ADUs (§28-33(a)(1)(D)). Maximum height is The same height limit as a single-family dwelling on the lot (§28-33(a)(3)(F)): 30 ft in every single-family district from AG through R1-5 and in R-2 and R-3 (§28-35.A-B tables). The 15-ft cap on ordinary accessory buildings expressly does not apply to an ADU (§28-133(e)); state law bars a stricter ADU height than the house's (A.R.S. §9-461.18(B)(5)). You are allowed up to 2 per lot — one attached plus one detached ADU on a qualifying lot.
Rear setback: 5 ft from the property line (§28-33(a)(3)(D)(I)), against a house rear setback of 15-40 ft by district; state law caps what the city may require at 5 ft (A.R.S. §9-461.18(B)(6)). Side setback: 5 ft from the property line (§28-33(a)(3)(D)(II)) — the state-law ceiling. The ordinance does not expressly relax the street-side setback on a corner lot (10 ft in R1-10 through R1-5, 20-25 ft in RR-18/R1-15/RR-43/R1-35, 40 ft AG under §28-35.A), so ask Planning before siting a casita on the street side. Front setback: The front yard setback of the zoning district under §28-35 (§28-33(a)(3)(D)(III)): 20 ft in R1-7, R1-6 and R1-5; 25 ft in R1-10, R1-8 and RR-18; 35 ft in R1-15; 40 ft in R1-35, RR-43 and AG; 20 ft R-2, 25 ft R-3 (§28-35.A-B; 5 ft less with a side-entry garage). A detached accessory building is never allowed in a front yard (§28-133(a)). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None — no additional parking space or in-lieu parking fee may be required for a new ADU (§28-33(a)(5); A.R.S. §9-461.18(B)(3)). But the lot may have only one driveway, shared by the house and the ADU, and a new ADU must use the existing driveway (§28-33(a)(3)(L)). 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 to build or to rent long-term — the ordinance says outright that either the house or any ADU may be separately leased as long-term rental housing (§28-33(a)(2)(C); A.R.S. §9-461.18(B)(1)-(2)). An ADU may not be sold separately from the house (§28-33(a)(2)(B)). Owner residence IS required to use an ADU finaled on or after September 14, 2024 as a short-term rental (§28-33(a)(7)) — see the rental section. 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 Avondale is typically Building applications: 16 business days for the first review and 8 for each subsequent review (Development Services review-timeline sheet, revised 10/31/2024). City business days are Monday-Thursday, and a submittal after 3 PM starts the clock the next business day. Plan check: Full residential plan review under the 2024 International Residential Code with Avondale amendments (Ord. 2046-1225, 12-1-25); valuation is set from the ICC Building Valuation Data table, with the Chief Building Official's figure final (IBC §109.3 as amended). The city may not require a commercial building code or a fire sprinkler (§28-33(a)(11); A.R.S. §9-461.18(D)); the amended IRC R309 makes sprinklers optional in one- and two-family dwellings. The ADU must connect to the house's utilities, the owner must show the services are adequate and upgrade them if not, and it may not sit on a utility easement without each easement holder's written consent (§28-33(a)(6)). Pre-approved plans availability: None available yet — Avondale has set up a Preapproved Housing Design Plan Program under A.R.S. §9-461.20 (Class 4: ADUs of exactly 200, 600 or 1,000 sq ft, at least three elevations per plan), but its Preapproved Plan Library said 'no preapproved residential plans available right now' on September 20, 2026. Users of a preapproved plan still pay permit and impact fees, may owe a design fee to the plan's author, and must sign a use-authorization and indemnification form.
Average ADU rental income in Avondale: 1-bedroom units rent for $1,400-$1,700/month, 2-bedroom units for $1,650-$1,950/month. Short-term rentals: Only if you live on the property: an ADU issued a certificate of occupancy on or after September 14, 2024 may not be used as a vacation or short-term rental unless the owner resides on the same property (§28-33(a)(7)); o. Expected ROI: 6-11% gross rental yield.
The minimum lot size for an ADU in Avondale is No ADU-specific minimum lot size — the one-attached-plus-one-detached allowance applies on lots under and over 1 acre alike (§28-33(a)(1)(A)-(B)); a lot of 1 acre or more can add a second detached unit if one is restricted-affordable (§28-33(a)(1)(C)). District minimums for the house itself run from 5,000 sq ft (R1-5) to 43,000 sq ft (RR-43) and 5 acres (AG) (§28-35.A). 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 Avondale, 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.
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