Building a casita in Gilbert: the rules, fees and the math

Gilbert is covered by Arizona's 2024 casita law, so an attached and a detached unit are allowed by right on a single-family lot with no owner-occupancy or extra parking requirement. Below is how Gilbert wrote that into its own code, read from the city's ordinance on October 7, 2026, and what the resale market here does to the decision.

The rules in Gilbert

Ordinance / code	Land Development Code Section 5.2.3, Accessory Dwelling Unit; Ordinance 2931 (case Z24-05)
Adopted	Effective December 18, 2024
Units allowed	One detached and one attached per lot in every single-family district; one more detached on an acre or more with an affordable unit.
Maximum size	Up to 75% of the main home's gross square footage. Units of 1,000 sq ft or less are by right with a building permit; a unit over 1,000 sq ft but under 75% needs an Administrative Use Permit and must sit inside the building envelope.
Larger lots	No size increase. Parcels of an acre or more may have one more detached unit if it is restricted affordable.
Setbacks	Units of 1,000 sq ft or less may sit outside the building envelope at 5 ft from rear and side lines for a unit up to 10 ft tall, plus 1 ft of setback for each foot of height above 10 ft (a 13-ft unit needs 8 ft). Larger units follow the district's envelope.
Height	The base district's height limit (accessory structures 20 ft in SF-15 through SF-6, 30 ft in SF-35 and SF-43).
Parking	None required.
Renting it out	The unit may be rented separately from the house with no owner-occupancy requirement. The town's general short-term rental licensing applies; we found no ADU-specific short-term rule.
Permit process	Up to 1,000 sq ft: building permit through the OneStopShop. Over 1,000 sq ft: Administrative Use Permit from Planning plus a building permit. A soils report is required unless one is on file for the subdivision or a waiver is signed.

A separate address may be requested but is not required, and a second electric meter is optional. Full ranges and ovens are allowed. Exterior standards cover articulation, accents and screening of ground-mounted equipment, with no requirement to match the house. The unit shares the house's refuse service.

Source: Town of Gilbert: Land Development Code; gilbertaz.gov; gilbertaz.gov. Read October 7, 2026.

Fees in Gilbert

Permit and plan review. Standard building permit fees; the town's ADU handout notes development fees may be assessed at permitting. No ADU-specific figure is published.
Impact fees. System development fees adopted April 2024 (amended December 2024 and December 2025); the single-unit residential schedule lists parks, traffic signals, roads, police and fire categories. We could not open the schedule itself, so figures are confirmed per address during the property review.

In June 2026 the state capped the development (impact) fees a city may charge an ADU for services other than water and sewer at the lesser of 25% of the single-family fee or the unit's proportionate share, and limited water and sewer fees to the unit's added demand (HB 2946, signed June 5, 2026). Most cities had not yet re-published schedules when we read them; Glendale's 25% ADU line is the first we found. Expect ADU impact fees to fall toward that cap. Governor's announcement.

What the state law guarantees here

Whatever the local code says, in Gilbert these points come from A.R.S. § 9-461.18 and the city cannot be stricter:

At least one attached and one detached ADU on any lot with a single-family home, as a permitted use (no public hearing, no variance)
A unit up to 75% of the main home's gross floor area or 1,000 sq ft, whichever is smaller (cities may allow larger)
A third, detached unit on lots of one acre or more if one unit is deed-restricted affordable
Separate long-term rental of either the house or the ADU (leases of 90 days or more, or month to month)

The math in Gilbert

Redfin's median sale price in Gilbert is $276 per square foot. A new casita builds for about $265 to $280 per finished foot and a garage conversion for about $120. That puts Gilbert in the "At the line" tier: one square foot of new casita, at the typical $272 build cost, comes out −$65 at a 75% appraiser credit and +$4 at full credit. A conversion clears at either credit.

The target areas page explains the tiers and the math page has the calculator. Rent is the other half: see rental math.

Owners and investors in Gilbert

Homeowners get a by-right unit for family, guests or long-term rent, with the same appraisal and lender rules as anywhere in the Valley.
Investors can treat the casita as the piece that moves a house out of its neighborhood's price band at resale, as our two Maryvale sales show on the case studies, and as monthly income in the meantime. Gilbert's rental rules above say whether both units can be let separately.
Either way the lot decides: setbacks, utilities, sewer depth and easements. Request a property review and we confirm the current Gilbert rules for your address.

Other city pages: Phoenix, Mesa, Chandler, Scottsdale, Tempe, Glendale, Peoria, Surprise, Goodyear, Buckeye.

Rules were read from Gilbert's published ordinance and planning material on October 7, 2026 and summarized in plain terms; this is not legal advice. Cities amend codes, and some parcels sit in zones the state law excludes (near military airports, in airport noise zones, on tribal land). We confirm the rules that apply to your parcel during the property review.

Request a property review

Find out what your property can hold.

Send the address and your goal. Anthony Alexander Lopez or Juan M Lopez Solano will review zoning, setbacks and utilities and reach out within one business day. No obligation, and no city approval implied: it is our professional read of your lot.

Prefer to talk? (602) 386-6623 · See completed projects