Maricopa County islands: the easiest place for a casita and a shop

What is a county island?

A county island is unincorporated land surrounded by a city. Your mailing address may say Gilbert, Mesa, Chandler or Queen Creek, but zoning comes from Maricopa County. Check your parcel's jurisdiction before you plan anything, since it changes every rule on this page.

County casita rules

• A 2025 law (HB 2928, ARS 11-810.01) applies the same basic ADU rules to unincorporated county land, with no population minimum. Counties had until Jan. 1, 2026 to adopt rules.
• Maricopa County's updated zoning ordinance, including its ADU rules, took effect Jan. 9, 2026 (county update page).
• Under these laws, cities and counties cannot require more than a 5-foot side or rear setback for an ADU, cannot require extra parking for it, and cannot require it to match your home's design.
• Cities and counties must allow an ADU of at least 75% of the home's interior living area or 1,000 square feet, whichever is less. Some allow larger ADUs with extra conditions.
• A detached ADU in the required side or rear yard is limited to 18 feet tall and 5 feet from the lot line.
• You can rent an ADU long-term (90 days or more, or month to month). The city cannot require the tenant to be a relative or employee.
• Short-term rentals are different: a city or county can require the owner to live on the property if it is a short-term rental with an ADU approved on or after Sept. 14, 2024 (HB 2928).

Why shops and RV garages fit here

In unincorporated Maricopa County, detached accessory buildings may sit in the required side or rear yard as close as 3 feet to the lot line, as long as they cover no more than 30% of that yard (Zoning Ordinance). That is more room than the 15 ft reduced-setback limits in Queen Creek, Chandler and Mesa.

Some islands are large-lot areas without an HOA. With no HOA, the county rules are your only gate, and a steel building may be an option.

More on costs: RV garage cost by size and RV garage with a casita.

A casita plus shop on an island lot

Plan the two parts separately:

• The casita follows the ADU rules: 5 feet from the line and 18 feet tall in the required yard.
• The shop follows the accessory building rules: 3 feet from the line within the 30% yard limit.

The ordinance does not say how it treats both under one roof, so ask the county before you design.

Example from our calculator: a 600 sq ft Standard casita plus a 24x45 stucco RV bay is about $233,400 to $291,000. Price your combo.

Island lot cost notes

Island lots are often bigger, so the casita may sit far from the house. Long trenches for power, water and sewer or septic add cost. Our calculator adds $4,500 to $8,000 for a long run or a new subpanel. Ask your builder about septic capacity early if you are not on sewer.

How to choose a casita builder in Maricopa County islands

We do not rank or recommend builders. Use this checklist with any contractor you talk to.

1. Check the ROC license. Search the contractor on the Arizona Registrar of Contractors site. Make sure the license is active and covers residential work, and that the name matches the bid.
2. Ask for proof of insurance. Get a certificate for liability insurance, and for workers' comp if they have employees.
3. Get a written bid. It should list plans, permits, site work, utility runs, the slab, AC and finishes, plus any allowances. Compare it line by line with our line items.
4. The contractor should pull the permits. Ask who pulls them. If you are asked to pull them yourself, ask why.
5. Tie payments to finished work. Avoid paying most of the price up front.
6. Ask for local projects. Ask whether they have pulled permits with Maricopa County, not just the nearby city.

Islands we cover

Unincorporated Maricopa County land in and around Gilbert, Queen Creek, Chandler and East Mesa. If you are not sure, the lot checker walks you through it.