Defensible Space on Arizona Horse Property and Hay Fires

The short answer: Defensible space on Arizona horse property means clearing and managing what can burn around your home, barn and other buildings. The Arizona Department of Forestry and Fire Management says to maintain at least 30 feet of defensible space around structures, and its Firewise guide tells owners to include barns. Hay adds its own risk: University of Minnesota Extension says hay baled at over 25 percent moisture is a high fire risk.

Defensible space on Arizona horse property is easy to overlook on a first showing. They are looking at the arena, the stalls, the view. But a barn full of hay, a stack of old fence rails, a propane tank, and dry weeds along the fence line add up to a real fire plan question.

I want to cover two things here. First, what Arizona's state forestry agency recommends for the space around your buildings. Second, the hay fire that starts on its own, and the numbers that tell you it is coming.

Defensible space is the area around a structure where you clear and manage what can burn, so a fire has less to feed on when it gets close.

The Arizona Department of Forestry and Fire Management, known as DFFM, put it plainly in a May 1, 2026 release: start with the structure itself and work outward at a minimum of 5 feet, clear debris from roofs and gutters, move flammable materials away from the home, and "maintain at least 30 feet of defensible space around structures."

Yes. DFFM's Homeowners' Firewise Guide for Arizona, dated June 2016, tells owners to include "detached garages, storage buildings, barns and other structures" in their plan.

The guide describes management zones:

• Zone 1 is at least 30 feet around the structure, measured from the outside edge of the eaves and any attached structures like decks or stairs. Flammable materials and vegetation are removed or replaced with noncombustible surfaces and fire-resistant plants.
• Zone 2 depends on slope. The guide says typically survivable space should extend at least 100 feet from the structure.

For grass and desert vegetation, the guide's chart lists 30 feet on slopes from 0 to 20 percent and 100 feet on steeper ground.

Inside Zone 2, the guide says to thin trees and shrubs "at least 10 feet between crowns," remove dead, dying or diseased trees and shrubs, and extend thinning along both sides of the driveway all the way to the main access road. On acreage with a long drive, that last one is easy to miss, and it is the road you and your trailer would be leaving on.

Yes, and DFFM encourages it. The agency's May 2026 release tells residents to "talk to neighbors about wildfire planning," and says DFFM is the state liaison to the National Fire Protection Association's Firewise USA program, with more than 215 Firewise USA-recognized communities across Arizona. If your road has several horse properties on it, a shared plan for cleared fence lines and evacuation routes makes sense.

One honest note. The guide says these are recommendations, and "they are not requirements nor do they take precedence over local ordinances." Your local fire department and your town's rules come first.

The same DFFM guide gives specific distances:

• Move firewood stacks and scrap lumber piles at least 30 feet from the house or other buildings.
• Propane tanks should be at least 30 feet from any structures, preferably on the same elevation as the house.
• Do not stack firewood or store other combustibles in Zone 1.

The guide does not list hay by name. My advice is to call your local fire department and ask where they want your hay stored. They would rather answer that question now than later.

Wet hay can heat up from the inside and ignite with no spark at all.

University of Minnesota Extension, in its "Preventing hay fires" guide, says "proper moisture at baling is the single biggest hay fire risk factor." Heat comes from bacteria respiration after baling. Here is its moisture table at the time of baling:

Extension's temperature table for the inside of the bale:

Extension also says to watch how fast the temperature climbs. A gradual increase usually has little fire risk, and "a rapid rise in temperature creates a high fire risk."

That last row is the one to remember. If a stack is that hot, do not start pulling bales apart yourself. Call the fire department.

Yes. The same Extension guide says moldy hay is especially dangerous to horses, causing colic, heaves and respiratory illness. It is also a health risk for people, through an allergic reaction called farmer's lung.

So when a load comes in, ask your hay supplier about moisture. Our guide to the true cost of feeding a horse in Arizona breaks down what feeding really costs here.

DFFM's guide says to "have means of transporting pets and livestock readily available," establish and practice an evacuation plan, and drive your travel routes in advance. For horse owners, that means a hitched-and-ready plan, not a trailer with a flat tire behind the barn. If your plan ever means hauling out of state, read our guide to relocating with horses and interstate transport.

• Leaving the barn out of the plan. DFFM's guide says to include barns and other structures.
• Stacking firewood or scrap lumber too close. The guide says at least 30 feet from the house or other buildings.
• Setting the propane tank too close. The guide says at least 30 feet from any structures.
• Forgetting the driveway. The guide says to extend thinning along both sides of the drive to the main access road.
• Pulling apart a hot hay stack yourself. At 175 to 190°F, Extension says contact the fire department.

I am Kim Williamson, REALTOR®, with REAL Broker, and I help buyers and sellers of horse property and acreage across the Metro Plex of Arizona. If you are buying, walk the property with this list in mind. Where is the hay stored? How close is the propane tank? What is piled against the back of the barn? None of it is a deal breaker. All of it is worth knowing. Check your coverage too. Our guide to insurance for Arizona horse property covers what is different on acreage.

If you are selling, clearing around your structures before photos is good safety and good marketing. Buyers notice a clean barn aisle and a cleared fence line. If you are new to your place, add this to your list from our guide to your first 90 days on horse property.

How much defensible space does Arizona recommend around a home? The Arizona Department of Forestry and Fire Management says to maintain at least 30 feet of defensible space around structures, starting at a minimum of 5 feet from the structure itself.

Should my barn be included in my defensible space plan? Yes. DFFM's Firewise guide tells owners to include barns, storage buildings and other structures in the plan.

At what moisture level is hay a fire risk? University of Minnesota Extension says hay baled at less than 15 percent moisture has a very low risk of fire, and over 25 percent is high fire risk.

What hay temperature means danger? Extension says 175 to 190°F means fire is imminent and to contact the fire department. Over 190°F, bales may combust when moved.

How far should propane tanks be from buildings? DFFM's Firewise guide says at least 30 feet from any structures.

Want more detail? These are the sources this article is built on (links checked October 4, 2026):

• Arizona Department of Forestry and Fire Management: "Prepare Now - Reduce the Risk of High Intensity Wildfire and Protect Your Home" (May 1, 2026)
• DFFM: "Living With Wildfire: Homeowners' Firewise Guide for Arizona" (June 2016, PDF)
• University of Minnesota Extension: "Preventing hay fires" (reviewed 2021)

Do your own due diligence. This article is general safety information to help you ask better questions. It is not a fire inspection. Always do your own due diligence and confirm the details for your specific property with your local fire department. Ask them for a look at your place, and where they want your hay stored.

Looking for horse property in the Metro Plex of Arizona that is set up right? I am Kim Williamson, REALTOR®, with REAL Broker, and I help buyers and sellers of horse property and acreage across the Metro Plex of Arizona. I have lived in Arizona 36 years, sold real estate here for 24 years, closed 1,000+ transactions, and I am an 8x WPRA World Champion. Call or text 480-206-1500, or start at www.ArizonaHorsePropertyForSale.com.