Defensible space: preparing the area around your home
Most homes lost to wildfire are not reached by the flame front but by embers. What to do in the first five feet, and out to a hundred.
When a neighbourhood burns in a wildfire, the photographs usually show intact houses next to gutted ones. The difference is rarely luck: it is the first few feet around each one.
The enemy is embers, not the wall of fire
A wildfire throws ahead a rain of embers that wind can carry more than a mile. Those embers land on roofs, in gutters, on decks and in corners full of dry leaves, and they ignite there long before the front arrives.
That is why a house can burn without the main fire ever reaching it, and why the highest-value work is not out in the woods but right against the siding.
The three zones
| Distance | Goal | What to do |
|---|---|---|
| 0 to 5 ft | Nothing ignites against the wall | Gravel or bare soil, no firewood, no plants |
| 5 to 30 ft | Break continuity | Spaced plantings, short grass, separated crowns |
| 30 to 100 ft | Slow the advance | Prune low branches, remove dead material |
Entry points almost nobody checks
- Gutters full of leaves. One ember lands there and starts a fire at the roof edge. Clearing them before the season is half an hour of work.
- Vents. Roof and crawlspace. Fine metal mesh keeps embers out while keeping the airflow.
- Under a wooden deck. If leaves and branches have piled up underneath, it is a firebox ready to light. Clear it and screen it.
- Firewood stacked against the house. Move it at least thirty feet away.
- Anything under the eaves. Whatever leans there acts as a wick.
Pruning without clear-cutting the yard
The idea is not to strip the lot but to cut the paths fire uses to climb. A surface fire becomes a crown fire when it finds a fuel ladder: tall grass reaching a shrub, a shrub reaching low branches, low branches reaching the canopy.
- Prune low branches up to about six feet from the ground.
- Leave space between crowns, especially on a slope.
- Remove dead branches, accumulated litter and dry shrubs.
- Keep grass short in the near zone.
- Wildfire evacuation: what to take if you have 15 minutes Wildfires move faster than any other disaster. What has to be ready beforehand and the order everything else gets picked up in.
- How to protect yourself from wildfire smoke indoors Smoke affects areas hundreds of miles from the fire and lasts for weeks. How to build a clean air room and which filters actually work.
Gear that covers this
Products that match what the guide above recommends.
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Fine metal mesh for vents
Embers enter through roof and crawlspace vents. Fine-mesh screening is one of the cheapest and most effective measures there is.
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Long garden hose
It should reach any point of the perimeter. Useful for putting out small ember spot fires before they become a house fire.
Frequently asked questions
What is defensible space?
The area around a home where vegetation and combustible material are reduced to slow the fire and give firefighters room to work. It is usually divided into zones by distance from the structure.
What actually ignites most homes in a wildfire?
Wind-driven embers, which can travel more than a mile ahead of the front and enter through vents, gutters full of leaves or wooden decks. Not the wall of flame.
Do I have to remove every tree around the house?
No. The goal is to break the continuity of fuel: separate crowns, prune low branches and remove the vegetation that connects the ground to the canopy and the canopy to the roof.
What should I clear first?
The first five feet against the walls, including gutters, the space under a deck and anything leaning on the siding. That is where embers land and where fire starts fastest.