What Is Defensible Space?

So far, our blog articles about fire-resistant construction and fire-resistant building materials have focused on what you can do to protect your home’s structure. However, protecting the area around your home is just as important. 

In the context of fire-resistant buildings, this area is called defensible space. Below, we’ll discuss more what defensible space is, what it entails, and some tips on how to keep yours well-protected.

What Is Defensible Space?

Defensible space is the buffer created between your home and the vegetated grounds that surround it. This vegetation can include both natural and landscaped elements, such as grass, trees, shrubs, and more. 

The purpose of defensible space is to design and maintain it in a way that mitigates fire hazards, either by slowing fires down or stopping them completely. If planned and executed properly, defensible space should: 

  • Eliminate paths for a wildfire to burn directly toward your home
  • Lower the chance of embers igniting other vegetation and materials near your home
  • Reduce radiant heat exposure to your home
  • Provide a safe space for you to evacuate your home
  • Provide a safe space for first responders to defend your home

4 Defensible Space Zones

An effective defensible space has a series of zones, each of which requires different actions to be taken. You should create these zones around each building on your property — don’t forget detached garages or storage buildings!

Let’s take a look at what these defensible space zones are, and what each of them requires. 

Zone 0 

Zone 0 is located 0-5 feet from your home (or other building on your property). It also includes the area underneath and around any attached decks. Since it’s so close to your home, it requires the highest level of care to reduce fire hazards and should be completely free of combustible materials. 

Here are some tips for what fire protection measures you can take in Zone 0: 

  • Use hardscaping materials like gravel or concrete, rather than combustible softscaping materials like bark or mulch.
  • Extract any dead or dying vegetation (grass, plants, trees, leaves, etc.) lying around. Make sure to check under your deck, on your roof, and in your gutters. 
  • Limit plants to low-growing, non-woody, properly watered plants. 
  • Clear away all tree branches within 10 feet of your chimney. 
  • Replace combustible fencing or gating materials with noncombustible options.

Zone 1

Zone 1 is located 5-30 feet from your home (or other building on your property), or to your property line — whichever is closer. 

This zone reaches a bit further away from your home but calls for important protective measures like: 

  • Extract any dead or dying vegetation (grass, plants, trees, leaves, etc.) lying around. 
  • Mow your grass so it’s no taller than four inches.
  • Trim tree branches often, so that they’re spaced no less than 10 feet away from other trees’ branches. 
  • Relocate any wood piles to Zone 2. 

Zone 2

Zone 2 is located 30-100 feet from your home (or other building on your property), or to your property line – whichever is closer. It’s the part of your property that’s furthest from your home but still requires a few preventative efforts to reduce fire fuel. Here’s what you can do:

  • Extract any dead or dying vegetation (grass, plants, trees, leaves, etc.) lying around. 
  • Mow your grass so it’s no taller than four inches.
  • Create horizontal and vertical space between plants and trees (more on this below). 
  • Ensure any exposed wood piles have at least a 10-foot clearance in all directions. 

Zone 3

Zone 3 is located much further away from your home (or other building on your property). It’s usually outside of your property line and therefore not your responsibility to maintain. However, it plays a large role in mitigating and responding to wildfires, so any way you pitch in and help is beneficial. 

The key initiatives here are to remove dead or dying vegetation that could fuel wildfires and to provide a safe, clear path for emergency responders to quickly reach your property. 

Other Defensible Space Considerations

Aside from the measures mentioned for each defensible space zone above, there are a few other considerations you can make to better protect your home from fire damage. They have to do with which types of plants you choose and how you choose to place them on your property. 

Choosing Fire-Resistant Plants

There are no “fireproof” plants — but there are some that contain higher moisture levels, grow closer to the ground, and/or have a low resin content. If your landscaping is currently outfitted with highly combustible plants, here are some more fire-resistant alternatives:

  • Trees – Opt for hardwood trees like maple or cherry, rather than softwood trees like pine or fir. 
  • Shrubs – Hedging roses, shrub apples, and bush honeysuckles are all good options. 
  • Flowers & other plants – Succulents, aloe, rhododendrons, and rockrose orchids all have fire-resistant qualities — and they’re beautiful to look at!

Spacing Plants & Trees

Plant type is one thing; plant spacing is another. Spacing your plants appropriately is a critical step in preventing the spread of wildfires. 

How far you space your plants apart is often dependent on your plants’ sizes and the slope of your land. If your property features a steep slope and larger plants, it’ll require more spacing between them. If your property features a level slope and smaller plants, it’ll require less spacing between them. Either way, adding space between plants is intended to limit that “chain reaction” effect of fires spreading from one plant to the other. 

Build Your Fire-Resistant Home and Defensible Space with Us

Fire-resistant construction is about more than just the structure itself; it’s also about the space surrounding it. If you’re interested in learning more about defensible space and how you can protect your property from devastating fire damage, contact Tectonic Design + Build. We’re dedicated to building Boulder, Colorado’s most fire-safe, resilient, healthy homes, and we’d be happy to help with yours! 

Looking for more information on defensible space? Check out these helpful resources: