How do I find out if I can build on a lot in Arizona?

You find out whether you can build on a lot in Arizona by checking seven things before you buy or design: who governs the parcel and how it is zoned, legal and physical access, water, wastewater, flood risk, the ground itself, and the private rules recorded against it. Most of the first pass is free public lookups you can do in an afternoon from the parcel number. The rest takes a title report, a survey, a soils report and a septic feasibility test. If any one of the seven fails, the lot may still be buildable, but it will cost more or take longer, so you want to know before you sign.

On unincorporated county land there is a head start built into state law. Under A.R.S. 33-422, a seller of five or fewer parcels outside a subdivision must hand you a written affidavit of disclosure at least seven days before the sale, and you can cancel within five days of receiving it. The affidavit asks most of the same questions below, so read it line by line and check every answer marked unknown.

1. Find out who governs the parcel and how it is zoned

Look the parcel up on the county assessor's map first. If a city or town name appears, that city's zoning code and building department decide what you can build. If it reads unincorporated, the county does. Our answer on telling whether a lot is in a city or the county walks through the lookup.

Then read the zoning district. It sets whether a single-family home is allowed at all, the minimum lot size, the setbacks from each line, the height limit and how much of the lot you may cover. A one-acre county lot in a rural district such as RU-43 plays by different rules than a city lot, as our page on rural residential zoning in Maricopa County explains. Setbacks, height and coverage together give you the buildable envelope, which is how big the house can be (see the biggest house you can build on your lot).

2. Confirm legal and physical access

A lot needs a recorded right to reach it, not just a dirt road you can drive. Legal access means the parcel fronts a public road or has a recorded easement to one. Physical access means a vehicle can actually get there. The affidavit asks about both separately, and it asks whether a surveyor or engineer has said the access can be driven by a two-wheel drive car, because counties apply that test when they review land splits under A.R.S. 11-831. A preliminary title report shows the recorded easements. Our guide to confirming legal access to a rural lot covers what to look for.

3. Prove where the water will come from

Inside a city, ask the water provider for a will-serve letter. On rural land, the answer is a private well, a shared well, a private water company or hauled water, and each changes the build.

• A new well. Arizona exempts small domestic wells, those with a pump of 35 gallons per minute or less, from most groundwater rules under A.R.S. 45-454. The same statute bars a new exempt well on land within 100 feet of the water lines of a city or town provider that holds an assured water supply designation, in the older active management areas such as Phoenix and Pinal, unless the state grants an exemption, for example when the provider will not confirm service or connecting would cost more than the well. Search the state's well records for neighboring wells to see how deep they went.
• A shared well. Get the recorded agreement before you buy. Our page on shared well agreements explains why it is your only protection.
• Hauled water. The affidavit must name the hauler and the source. Ask a lender early, since some loans treat a hauled-water home differently (see financing a hauled-water home).

A parcel split from a larger one, five lots or fewer, may never have passed the state's 100-year water test, which is how much of the Rio Verde Foothills was built (see wildcat lot splits).

4. Check that the soil can take a septic system

Where there is no sewer, the house needs an on-site wastewater system, and the county will not issue a building permit without approval for one. That approval starts with a site investigation and a percolation test, which shows whether the ground can absorb the water. A shallow rock layer, a steep slope or a wash through the lot can rule out a standard system and call for an engineered one. The septic area also has to sit at least 100 feet from any well, yours or a neighbor's, so a small lot can run out of room (see well to septic distance).

5. Look up the flood zone and the washes

Enter the address on FEMA's Flood Map Service Center to see whether any part of the lot sits in a mapped floodplain. In Maricopa County, the Flood Control District's floodplain information adds local studies and the floodplain use permit you may need. A lot can be outside FEMA's map and still have a desert wash that floods in the monsoon, so walk it after a storm if you can. A house in a floodplain is often still buildable, but the floor may have to sit higher and a federally backed mortgage will require flood insurance.

6. Know the ground: fissures, problem soils and slope

Groundwater pumping has opened earth fissures and caused subsidence in parts of the Valley and Pinal County, and expansive clay and caliche are common across the state. The Arizona Geological Survey maps both, and the affidavit asks about them. Screen the parcel there, then order a soils report, which most building departments and lenders ask for anyway (see whether you need a soil test and earth fissures in Pinal County). A steep or rocky lot is buildable too, but grading, retaining walls and the foundation will cost more.

7. Read the recorded rules: easements, HOA and overlays

The title report lists what is recorded against the land: utility easements that cut through the middle, a road easement for a neighbor, deed restrictions, and an HOA's CC&Rs with their own setbacks, size minimums and design review. In North Scottsdale and similar desert areas, a building envelope and a natural area easement can put much of a large lot off limits to building (see building envelopes and NAOS easements). Some towns add hillside, dark-sky or height rules on top of zoning, so ask the planning counter which overlays apply.

Utilities and the cost of getting them there

Ask the electric company how far the nearest line is and what an extension would take, and confirm whether gas, phone and internet reach the lot. Distance to power is one of the biggest swings in a rural budget, as our answer on extending power to a rural lot shows, and it belongs with the rest of site work in the numbers before you buy.

What you can check yourself and what needs a professional

• Free, from the parcel number: jurisdiction and zoning, the FEMA flood map, the fissure and soils maps, nearby well records, and whether a water provider serves the area.
• From the seller: the A.R.S. 33-422 affidavit on unincorporated land, any HOA documents and any existing septic or well records.
• Paid, before you close: a preliminary title report, a boundary survey, a soils report, a septic site investigation and percolation test, and will-serve letters from the utilities.

Make the purchase contract contingent on those reports where you can, so a failed test lets you walk away.

How Jematell Homes checks a lot

Building on land you own is our specialty. When you build on your lot with Jematell Homes, we check the lot for utilities, access and grading first, then handle the permits, engineering, site prep and the build. If you do not have land yet, our licensed real estate agents can help you find and buy a lot that passes these checks. We build across Scottsdale, Phoenix, Cave Creek, Carefree, Fountain Hills, Paradise Valley, the Rio Verde Foothills and Pinal County. Call (602) 421-5576 or tell us about the lot you are considering, and confirm the rules for your specific parcel with your city or county before you buy.

Sources

• A.R.S. 33-422 (Land divisions; recording; disclosure affidavit)
• A.R.S. 11-831 (Review of land divisions)
• A.R.S. 45-454 (Exemption of small non-irrigation wells)
• FEMA Flood Map Service Center
• Flood Control District of Maricopa County: Floodplain Information
• Arizona Geological Survey: Problem Soils
• Arizona Department of Water Resources: Well Record Search