Everything homeowners ask about building an ADU in Gilbert — answered with 2026 data.
Yes, ADUs are allowed in All single-family zoning districts (SF-43, SF-35, SF-15, SF-10, SF-8, SF-7, SF-6, SF-D, SF-A): an ADU under 1,000 sq ft is a permitted (P) use and one over 1,000 sq ft needs an Administrative Use Permit (A) (LDC Table 3.1.2 and Section 5.2.3, Ord. 2931 eff. Dec 18, 2024). In commercial, office and employment districts an ADU is allowed only as a facility-manager unit (note L34). Tribal land and high-noise airport areas are outside the state mandate (ARS 9-461.18.G). in Gilbert, AZ. The maximum size for a detached ADU is 75% of the primary home's gross floor area (interior habitable area), measured by LDC Section 2 'Gross Floor Area'. Up to 1,000 sq ft is by right; from 1,001 sq ft up to the 75% cap the unit needs a $1,000 Administrative Use Permit and must be inside the building envelope (LDC 5.2.3.4.c, 5.2.3.A-B). State floor: the lesser of 75% or 1,000 sq ft must be permitted (ARS 9-461.18.A.3). Attached ADUs can be up to Same as detached: 75% of the primary home's gross floor area, by right up to 1,000 sq ft, Administrative Use Permit above that. 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 $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: a $150,000 valuation is $1,145 permit plus $744.25 plan review (65% of the permit fee), about $1,890; add a $1,000 Administrative Use Permit if over 1,000 sq ft (Development Services Fee Schedule, Res. 4563 eff. July 1, 2025, revised Sept 15, 2026). to your budget. See our detailed Gilbert ADU cost guide.
Detached ADUs in Gilbert can be up to 75% of the primary home's gross floor area. Attached ADUs are limited to Same as detached: 75% of the primary home's gross floor area, by right up to 1,000 sq ft, Administrative Use Permit above that. Junior ADUs (JADUs) have a cap of Not a category in Gilbert or in Arizona law. A unit converted inside the house counts as the one attached ADU allowed per lot and follows the same 75% cap (LDC 5.2.3.3). Maximum height is Same as the base zoning district (LDC 5.2.3.4.b): 30 ft / 2 stories in SF-10, SF-8, SF-7 and SF-6; 35 ft / 2 stories in SF-43 and SF-35; 36 ft / 3 stories in SF-D and SF-A (Tables 3.2.4.A-I.1). Height is measured from finished floor or grade, whichever is lower, to a flat roof or the midpoint of a sloped roof (ADU Guide). Every foot over 10 ft adds 1 ft to the rear and side setback. You are allowed up to One detached and one attached ADU per lot; a second detached ADU on parcels of one acre or more if at least one ADU is a restricted-affordable unit on a qualifying lot.
Rear setback: 5 ft minimum for an ADU up to 10 ft tall; add 1 ft for every foot of height over 10 ft (a 13-ft unit needs 8 ft). Units of 1,000 sq ft or less may sit inside the rear setback area; units over 1,000 sq ft must stay within the building envelope, i.e. the district rear setback of 20-40 ft (LDC 5.2.3.A.1-2, 5.2.3.B.2). State cap: 5 ft (ARS 9-461.18.B.6). Side setback: 5 ft minimum for an ADU up to 10 ft tall; add 1 ft for every foot of height over 10 ft. Units of 1,000 sq ft or less may sit inside the side setback area; larger units must be within the building envelope (district side setback 5-30 ft) (LDC 5.2.3.A.1-2, 5.2.3.B.2). No ADU may be built over a public utility easement without the utility's written consent (LDC 5.2.3.4.d). Front setback: Same front setback as the primary house in its district (LDC 5.2.3.A.2.a): 20 ft in SF-8, SF-7 and SF-6; 25 ft in SF-10; 40 ft in SF-43 and SF-35 (Tables 3.2.4.A-G.1). Planned Area Development overlays may modify these. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None required for an ADU. Gilbert's LDC 5.2.3 sets no ADU parking standard and the town may not require added parking or in-lieu fees (ARS 9-461.18.B.3). 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. LDC 5.2.3.4.f allows the ADU to be rented separately from the house, and ARS 9-461.18.B.1-2 bars any owner-residency or family-relationship test for long-term rentals (90 days or longer, or month to month). Short-term rentals need a Town STR licence (see rental). 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 Published review goals: 12 working days for the first review of a single-family plan set and 8 for the second (room additions 8/4); Express Permitting reviews eligible detached residential structures in 1-3 working days for the plan-review fee plus 60% (Project Review Time Frames, Mar 2026). Plan check: Full construction plan review through the One Stop Shop; a soils report is required unless the subdivision has one on file or you sign the Town's soils waiver; a third or later review may be billed at $150 per hour; expedited review costs twice the plan-review fee (Fee Schedule pp. 8-9; ADU Guide). Pre-approved plans availability: None published on gilbertaz.gov as of Sept 20, 2026. ARS 9-461.20 (SB 1529, Laws 2025 ch. 259) requires every Arizona municipality to offer at least three pre-approved ADU design plans from July 1, 2026; ask the One Stop Shop whether Gilbert's are available.
Average ADU rental income in Gilbert: 1-bedroom units rent for $1,500-$1,800/month, 2-bedroom units for $1,850-$2,300/month. Short-term rentals: Yes, with a Town of Gilbert Short-Term Rental licence (registration through Neumo/GovOS; licence and renewal fee $250 from Oct 1, 2026), an ADOR TPT licence and written notice to adjacent neighbors (STR ordinance adopted. Expected ROI: 6-11% gross rental yield.
The minimum lot size for an ADU in Gilbert is No ADU-specific minimum lot size: any lot where a single-family home is allowed qualifies (ARS 9-461.18.A; the old 6,000 sq ft use-permit threshold is gone). Combined building footprints must stay within the district lot-coverage cap: 45% one-story / 40% two-story in SF-10 through SF-6, 30% in SF-43 and SF-35 (LDC 5.2.3.4.a, Tables 3.2.4). The ADU must be built after the primary home (LDC 5.2.3.2). 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 $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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