ADU rules in Gilbert

One detached ADU per lot as of right in all single-family districts (use table lists ADU under 1,000 sq ft as P in SF-43 through SF-A); a second detached ADU is allowed on parcels of one acre or more if at least one ADU is a restricted-affordable unit.

One attached ADU per lot in addition to the detached ADU.

An ADU must be subordinate to the primary dwelling and cannot exceed 75% of its gross square footage, and it is also capped by the base district's lot coverage and height limits. At or under 1,000 sq ft (and under 75%) an ADU needs a building permit only. Table 3.1.2 lists 'Accessory Dwelling Unit Over 1000 SF' as an Administrative Use Permit use only in SF-43, SF-35, SF-15, SF-10, SF-8, SF-7 and SF-6; the SF-D and SF-A columns are blank, and Section 3.1.2(C) prohibits uses not listed, so on SF-D and SF-A lots an ADU cannot exceed 1,000 sq ft. Facility Manager ADUs in non-residential districts are capped at 2,000 sq ft of livable area.

No owner-occupancy requirement appears anywhere in the LDC (searched full current text), and state law prohibits requiring any familial, marital, employment or other preexisting relationship between the owner or occupant of the main dwelling and the ADU occupant.

Section 5.2.3 sets no parking standard and the LDC off-street parking table (Section 5.3) has no ADU row; state law bars municipalities from requiring additional parking (or fees in lieu) to accommodate an ADU.

ADUs up to 1,000 sq ft are a permitted use in every single-family district (SF-43 through SF-A) and need only a building permit. ADUs over 1,000 sq ft but under 75% of the primary dwelling's gross floor area require an Administrative Use Permit plus a building permit, and are available only in SF-43 through SF-6. The Administrative Use Permit is decided by the Zoning Administrator after mailed neighborhood notice, but the Zoning Administrator may send an application of special neighborhood or community significance to a Planning Commission public hearing, and decisions can be appealed to the Planning Commission.

LDC 5.2.3(4)(f) states 'Separate renting or leasing of ADUs from the principal dwelling is permitted' (mirrors A.R.S. 9-461.18(B)(1), which bars prohibiting separate long-term rental). Short-term rentals of any dwelling need an annual town license under Municipal Code ch. 14, art. III (Sec. 14-78), which LDC 5.1.2 incorporates, within Arizona's state-preempted STR regime (A.R.S. 9-500.39). Gilbert has not adopted the optional owner-residency condition that A.R.S. 9-500.39(B)(9) allows for STRs on properties with an ADU approved on or after September 14, 2024, and no ADU-specific STR rule appears in the code. Ordinances 2993 to 2995 (adopted 9-1-2026, effective 30 days later) raise the STR license fee from $100 to $250, raise the unlicensed-operation penalty to up to $1,000 per month, and add notice-of-violation and citation procedures.