Yes. Mesa exempts a small detached shed from a construction permit only if it is under 200 square feet and has no electrical, plumbing or mechanical connections. Any structure with plumbing connections needs a construction permit, and a casita or other detached structure over 200 square feet needs approval too.
What do Mesa's FAQ and code say about sheds and plumbing?
The city's Residential Construction FAQ answers two questions on this. The first is about sheds and playhouses:
"You can build a detached shed or playhouse if it is under 200 square feet and has no electrical, plumbing, or mechanical connections without a construction permit. Height and location requirements do apply."
The second is about shops:
"Detached accessory structures larger 200 square feet require approval. Any structure with electrical, plumbing, or mechanical connections require a construction permit. Minimum building code, height, and location requirements do apply."
Put the two together and you get a short rule. A small shed with no utilities needs no construction permit. A detached structure over 200 square feet needs approval. Any structure of any size with plumbing needs a construction permit. Height and location rules apply to all of them, and those come from a different office, which we cover below.
What does the code add? The exemption in the code is narrow. Section 4-1-4(B)(1)(a) says a building permit is not required for one-story detached accessory structures used "as tool and storage sheds, playhouses, and similar uses," if the floor area does not exceed 200 square feet. The exemption does not apply if the property is subject to the Desert Uplands Development Standards, is in a Historic Preservation Overlay District, or is a designated historic landmark.
That exemption is about the building permit. The plumbing work is a separate matter. Section 4-1-4(A) says anyone who intends to install, alter, repair, remove, convert or replace any electrical, gas, mechanical or plumbing system covered by the code must first apply to the Building Safety Director for the required permit. The exempt-work list in section 4-1-4(B) does not include new plumbing for a detached building. It does include narrow items, such as equal replacement of an exterior water supply line or an exterior sanitary drain line to a building, but those are replacements of what is already there, and they exclude work in a public utility easement or City of Mesa right-of-way.
So a storage shed with nothing inside is exempt, and the same shed with a utility sink is not.
How is a casita different from a shed?
The city's exemption is for tool and storage sheds, playhouses and similar uses. A casita is a different kind of building. It is meant to be lived in, so it will have plumbing, and the city's list of jobs that need a construction permit includes several that describe one:
- Installing or modifying electrical, plumbing or mechanical systems
- Converting non-livable space to livable space
- Building a detached structure over 200 square feet
A garage converted to a casita would likely fall under the second line. A new backyard guest house would likely fall under the first and third. The city's FAQ does not use the word casita, so call the Planning Division before you design one. They can tell you whether your zoning allows the use, and what approvals you need.
Who do you call, and in what order?
The city's Residential Construction page lays out the steps, and the first is planning, not permits.
- 1Check zoning with Planning. Before you start, contact the Development Services Planning Division to see if the project is allowed in your zoning area or needs additional approval. Their contact is Planning.Info@MesaAz.gov or 480-644-4726. Height and location rules come from this office.
- 2Learn the permit rules. The city says a construction permit is required for installing or modifying plumbing systems. It also lists a warning for flood zones: if your property is in one, you must get approval from the Maricopa County Flood Control District before you apply for a Mesa construction permit.
- 3Check whether you need a licensed contractor. The city points to the Arizona Registrar of Contractors rules and says owner-occupied projects may not require a licensed contractor. The city's permit application also asks for a contractor licensure verification form. Our page on doing your own plumbing in Arizona covers the state rule.
- 4Prepare documents and apply. For additions, remodels and accessory structures, the city lists a contractor licensure verification form, a fully dimensioned site plan, a code data sheet with scope of work, and electrical, plumbing and mechanical plans. You apply online through the city's DIMES system.
For questions on the permit and the code, the FAQ lists Permit Services at 480-644-4273.
Do HOA rules or other approvals matter? They can. If your neighborhood has an HOA, ask it before you build, because the city's permit is a separate approval. Historic and Desert Uplands properties have their own limits, as the code exemption shows.
What does the plumbing inspection cover?
Once a permit is issued, the city inspects the work. Section 4-1-5 of the code says rough inspection of plumbing, mechanical, gas and electrical systems "shall be made prior to covering or concealment, before fixtures or appliances have been set or installed." It also says building service equipment regulated by the technical codes "shall not be connected to the water, fuel, or power supply, or sewer system until authorized by the Building Safety Director."
In practical terms, that means the trench, the pipe and the connection are visible for the inspector before anything is buried or covered. It also means the new building should not be hooked up to the house's water or drain until the city signs off. Plan the schedule around it so the trench does not sit open longer than it has to.
Digging brings its own step. The city's FAQ tells fence builders to contact Arizona 811 before they dig, and the same habit applies to a trench for a new water line or drain. A tie into the public sewer is covered separately. Our guide to Mesa's building sewer connection permit rules explains when a connection to the public sewer needs its own written permit.
When should you call a plumber?
Call a plumber before you frame the building, not after. Where the drain will run, how deep the water line goes, and where the vent will come out are all easier to fix on paper than in the ground. A licensed plumber can help you plan the plumbing so the permit application is complete the first time. For a related topic, see our guide on what plumbing work needs a permit in Phoenix, and how Mesa handles the tank to tankless swap.
Planning a casita, a shop or a plumbed shed? HQ Plumbing and Air can look at the plan with you. We are licensed and insured, and we give free estimates.