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; not permitted in R-4 (Avondale Zoning Ordinance §28-32 land use matrix). Only where the district allows a single-family dwelling, and never on a lot with a duplex, townhome or other multi-family development (§28-33(a)(3)(B)). Excluded: tribal land and land in the territory in the vicinity of a military airport, an FAA commercially licensed or general aviation airport, or a public airport (§28-33(a)(12)) — Luke Air Force Base and Phoenix Goodyear Airport are both nearby, so ask for 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 (Avondale Zoning Ordinance §28-33(a)(3)(A)); gross floor area means interior habitable area. No more than two bedrooms (§28-33(a)(3)(G)). Attached ADUs can be up to Same cap — the lesser of 75% of the house's gross floor 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 $120,000-$245,000. The cost per square foot averages $145-$270. Garage conversions are more affordable at $55,000-$135,000, while prefab ADUs cost $85,000-$200,000. Permit fees add Building permit and plan review fees apply — confirm current amounts with Avondale Development Services 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 gross floor 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 ordinance has no junior ADU designation. Maximum height is The same height restrictions that apply to a single-family dwelling on the same lot (§28-33(a)(3)(F)) — the 15-foot cap on ordinary accessory buildings 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 feet from the property line (§28-33(a)(3)(D)(I)); state law caps what the city may require at 5 feet (A.R.S. §9-461.18(B)(6)). Side setback: 5 feet from the property line (§28-33(a)(3)(D)(II)) — the state-law ceiling. Front setback: The front yard setback of the applicable zoning district under §28-35 (§28-33(a)(3)(D)(III)); detached accessory buildings are 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 (§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 (§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)), matching state law. Owner residence IS required for short-term rental of any ADU issued a certificate of occupancy on or after September 14, 2024 (§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 Confirm with Avondale Development Services at (623) 333-4000 — the city recommends a call about ADU requirements before submitting, and publishes no ADU-specific review timeline. Plan check: Full residential plan review under Avondale's building, fire and public-health codes, but 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 ADU must connect to the same utilities as the house, and the owner must show the services are adequate and upgrade them if not (§28-33(a)(6)); it needs its own entrance and an egress path that does not pass through the main house (§28-33(a)(3)(H)). Pre-approved plans availability: No city pre-approved ADU plan library found — confirm with Avondale Development Services.
Average ADU rental income in Avondale: 1-bedroom units rent for $1,250-$1,550/month, 2-bedroom units for $1,450-$1,850/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)). Owners who can show they had a legal right to build an ADU on or before September 14, 2024 are exempt, unless the three-year limit in A.R.S. §12-1134(G) has run. Arizona TPT registration applies. Long-term leasing of the ADU on its own is expressly allowed (§28-33(a)(2)(C)). Expected ROI: 5-8% annual return.
The minimum lot size for an ADU in Avondale is No ADU-specific minimum lot size — the same one-attached-plus-one-detached allowance applies below and above 1 acre (§28-33(a)(1)(A)-(B)); a lot of 1 acre or more unlocks a third unit. 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 $55,000-$135,000. 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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