Everything homeowners ask about building an ADU in Gilbert — answered with 2026 data.
Yes, ADUs are allowed in All single-family zoning districts (Gilbert Development Services ADU guidance; ARS 9-461.18) in Gilbert, AZ. The maximum size for a detached ADU is 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%). Attached ADUs can be up to 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%). Gilbert has an ADU-friendliness score of 6/10. Check our full Gilbert ADU rules page for complete zoning details.
ADU construction in Gilbert typically costs $130,000-$260,000. The cost per square foot averages $150-$280. Garage conversions are more affordable at $60,000-$140,000, while prefab ADUs cost $90,000-$210,000. Permit fees add Building permit and plan review fees based on valuation — Confirm with Gilbert Development Services to your budget. See our detailed Gilbert ADU cost guide.
Detached ADUs in Gilbert can be up to 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%). Attached ADUs are limited to 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%). 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 for single-family homes — Confirm with Gilbert Development Services. You are allowed up to 2 per lot (1 attached + 1 detached); a 3rd detached ADU allowed on parcels over 1 acre if it is a restricted-affordable unit on a qualifying lot.
Rear setback: 5 feet maximum required (ARS 9-461.18 caps rear setbacks at 5 ft). Side setback: 5 feet maximum required (ARS 9-461.18 caps side setbacks at 5 ft). Front setback: Per underlying zoning district — Confirm with Gilbert Development Services. 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). 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; no familial or pre-existing-relationship test allowed. 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 Gilbert is typically Confirm with Gilbert Development Services (480-503-6700). Plan check: Full construction plan review required — Confirm with Gilbert Development Services. Pre-approved plans availability: No pre-approved plan library — Confirm with Gilbert Development Services.
Average ADU rental income in Gilbert: 1-bedroom units rent for $1,500-$1,750/month, 2-bedroom units for $1,850-$2,300/month. Short-term rentals: Arizona law allows STRs with registration; ADU-specific STR conditions — Confirm with Gilbert Development Services. Expected ROI: 6-9% annual return.
The minimum lot size for an ADU in Gilbert is No ADU-specific minimum (the old 6,000 sq ft use-permit threshold was preempted); ADU must be built after the primary residence. 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 Gilbert, 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.