Natural wildfires have been increasing in frequency and severity in recent years. Land owners can take concrete steps to protect themselves, their family, and their property by following purposeful design choices. This puts the power in your hands.  No matter the global climate or political leadership, you can improve the safety and security of your site as soon as you’d like.

Outline

Main points for fire mitigation
Primary recommendation
How to approach planning a landscape design to guard against fire
Assessing the fire threat sector
Fire management zones
Additional advice
Plant details
Where NOT to plant
Conclusion
Resources

Main points for fire mitigation

A fire needs three things:

  1. Oxygen
  2. Heat
  3. Fuel

Fuel is the only one we can really control. That’s why we see everyone everywhere suggesting that land managers remove any backlog of fuel which is already building up in the natural environment.

Beware any of the edges or corners of your building; anywhere wind and wind-born particulate can build-up or swirl about. You see, it’s actually embers drifting on a breeze from a far-off fire which contribute to the most number of homes lost. If you look at a fire from afar, then of course there is a burning front which advances towards fresh material. But if you zoom in, that burning edge is disproportionately advanced by the ashes, embers, and sparks blown forward of the main fire. If they can land and heat the right spot, they start the blaze which speeds the wildfire.

When designing your house for fire resistance, look to minimize or protect:

  1. Roof overhangs and eaves
  2. All interior corners of your building’s siding (see the green circle, not the red no symbol)
  3. Flame contact from adjacent material itself catching fire
  4. Radiant heat from nearby structures burning

You can see from these points that keeping the area immediate surrounding your house is incredibly important.

The primary recommendation

Maintain a 5’ barrier which keeps vegetation separate from the house. Measure these five feet at least from the foundation, but preferably from the edge or dripline of the building’s eaves.

How to approach planning a landscape design to guard against fire

First, as a classic tenet of permaculture, assess the site’s sectors. In particular, in this case, your fire threat and wind sectors. Then, create a design in response.

Assessing the fire threat sector

  • Slope – the top of landscapes are always the most vulnerable position. Slope trumps wind.
  • Fuel – maintenance plans to minimize and design plans to isolate and insulate your landscape from spreading fire.
  • Wind – least important factor of the three, which is convenient because it’s hard to control. Only extreme wind conditions can overcome slope barriers.

Fire management zones

Another overlap with permaculture planning is breaking the site into zones. In this case, we have three zones with standard/minimum distances to direct landscape maintenance. There is an optional fourth zone which could apply to a large enough site (>100’ from any buildings) and if the land managers wanted to expend the effort to maintain the area.

  1. Immediate area
    • Zero to five feet (0-5’)
    • Create a totally non-combustible zone for the first five feet next to your house.
      • A great feature of hardscaping? It’s non-combustible! Use pathways and other design options to provide protection and utility at the same time.
  2. Near area
    • Five to thirty feet (5-30’)
    • Create a base of fire-resistant plantings to form a secure foundation. Depending on your situation, you could also think of this as ‘keep it green and healthy near the house.’
      • These plants should be clumped, like a patchwork across the landscape. Even if you don’t reduce the overall density of plants on the landscape, the plants are not offering a continuous blanket of fuel for the fire to use to advance.
      • There is the option to irrigate this near area. First, it’s still close to the house and so a sprinkler system will be easy to pressurize. But, perhaps more importantly, this provides a lush, wet environment to act as another defense against any incoming fire. In this manner, you’re gaining yet another use from your water as it’s not only beautifying the landscape but acting as natural insurance against supernatural disasters.
  3. Mid area
    • Thirty to one hundred (30-100’)
    • The goal here is to simply reduce the fuel load in this part of the ecosystem. The area included in this zone is exponentially greater than the previous zone and so labor should be applied conservatively.
      • A judicious land manager might direct the creation of hügelkultur mounds with the felled and thinned biomass from this zone.
      • Perhaps someone would like to make biochar!
      • If you have livestock, rotational grazing is a great option to keep undergrowth down. This kind of silvopasture can really help reduce the work humans have to do to maintain the landscape.
  4. Far area
    • One hundred feet and further (100’+)
    • Just do what you can: reduce the fuel load!
    • Trim, thin, and ‘limb up’ on any land left on the property.
      1. Limb up means creating 15’+  clearance to lowest limb. This prevents ‘fuel laddering’ where the fire rises from the ground to the tree’s crown.
    • Depending on your budget and space, you can use this far area to create a perimeter of low-lying ground cover which can be pre-emptively burned (and preferably bordered by sprinklers). I can’t think of any designer who would suggest this to you—can you think of the insurance premiums after they find out they told a client to set fire to their own property? Still tho, it is an option available to you, one used for time immemorial. If you don’t want to burn an entire band of your landscape, you could burn a patchwork into the landscape. The goal here is to reduce and isolate potential fuel and ignition sources. These are called ‘prescribed’ or ‘managed’ burns or fires. Don’t underestimate fire, tho, and seek to have an excess, overabundance of control options on-hand if you ever pursue this course of action.

Additional advice

Mulch can burn as well. Keep it away from your house as well, make fire breaks in your mulch as well. Bark mulch is more likely to smolder, slower than needle mulch (really this is just a recommendation for greater particle size and density, basic rules of making something harder to burn/less combustible).

Bias hardscapes towards the direction of the most likely fire danger. This will provide the least combustible materials for the most likely direction of incoming sparks. Make them work for it and have to travel just that much further if they want to try to light your house on fire!

Irrigated grass walkways or hardscaping can be use to isolate islands of plants while providing fuel breaks across the landscape.

Emergency sprinklers will be worth every cent spent if they are ever activated to save your house from a wildfire. This could mean adding additional sprinklers along your landscape’s perimeter. These will, of course, be on a separate circuit and always off unless and until needed. A last, but effective, line of defense is to install another emergency circuit of sprinklers on any structure’s roof! And now, one final detail: a good design will ensure these emergency sprinkler circuits are gravity-fed with emergency water stored high on the landscape. After all, if the emergency sprinklers are needed, then it’s a disaster scenario and we don’t want to count on anything and have back-ups for everything.

You can also use water reservoirs high on the landscape to flood a region below. Maybe it holds enough water to fill a an entire pasture between you and the fire with three inches of water. Maybe it rushes down to fill a modern moat, a berm or swale designed not for percolation and groundwater recharge but for simply being a wide swath of water as a hard barrier for any advancing line of fire.

All this talk of reservoirs demands I point out that concrete reservoirs are less damaged by fire than many other materials. And when you’re building for these scenarios, try to put your emergency water pipes underground where they’ll be protected so they can do their job of protecting your landscape!

Plant details

Spacing between plantings needs to increase when: there is a steeper slope, taller vegetation, and/or when in a more fire prone site.

Slope severityCanopy height for distance between plant groupings
No slop2x
20-40%4x
40%+6x

Fire resistance features:

  • Low growing
  • Open structure
  • Least resinous
  • Hardwoods > softwoods

All plants can burn.

Plant fire-resistant ones which are known to survive fires and regrow afterwards (always planning for the worst).

Minimize maintenance so that it doesn’t accumulate fuel, especially if you stop maintaining the plant.

Look for plants with high overall moisture content in their biomass.

Where NOT to plant

  • Under vents and eaves or adjacent to siding as this can quickly lead to sparks entering vulnerable parts of a house.
  • Under or near decks as that’s just a lot of fuel waiting to move a fire from your planted landscape to your house itself!
  • On the tight or inside corners of the structure as these areas can trap combustible debris and also have the greatest ratio of ground to the house’s surface area. Remember this pic? Give extra caution to these kinds of corners on any structure.

See both primary recommendation and immediate area both for reminders not to plant so close to your house! Five feet away form your house, minimum!

Conclusion

This is all the basic information you need to plan a robust landscape design that can not only resprout after a wildfire but also protect your property during the wildfire itself!

If you’d like to learn more about this topic, I encourage you to look for resources from both California and Australia; both places really pushing the frontier of fire research and fire mitigation education work.

If you would like to let an expert landscape designer take care of this concern for you, then reach out to me right now! The next fire could be right behind the next hill. I’ve seen it happen; I’ve evacuated from those fires, I’ve traveled those ash-covered & post-apocalyptic-looking landscapes.

Resources

CA Fire Sci. Consortium (2016): https://www.youtube.com/watch?v=DJfzAdsk8H8

UC – Ag and natural resources: https://ucanr.edu/sites/forestry/Wildfire/

Australian Institute of Architects – site planning & design for bushfire: https://www.architecture.com.au/wp-content/uploads/Acumen_Site-planning-and-design-for-bushfire_Australian-Institute-of-Architects.pdf