Brush Clearance: The First 100 Feet

How far does brush clearance reach around a house in Santa Clarita?

One hundred feet. That is the defensible space figure the Los Angeles County Fire Department and the City of Santa Clarita use for a home on a graded lot in the valley, measured outward from the structure, and it is the number a brush inspection starts from. The first 30 feet is the zone that gets the most work: grass cut to 4 inches or less, no dead material on the ground, no shrubs under a window or against a vent. The next 70 feet is thinning, not clearing, and on a slope the distance grows with the grade. For the household side of the same problem, the habits that keep a fire from starting inside the house, the alarm checks, the escape plan and the first aid for a burn, are covered by Fighting Burns, an editorial desk on fire prevention and burn care.

A house on a 20 percent slope needs more than a house on flat ground, because fire moves uphill faster than it moves across a lawn. The county fire department's brush clearance standards scale the distance with the slope and with the size of the vegetation, and the inspection is done against those standards, not against a single number for the whole valley.

Which months does the clearance deadline fall in?

The deadline is the first week of June, and the inspections that follow it run through June and July. Los Angeles County Fire Department brush clearance inspections begin in May in some areas and the formal compliance date for most Santa Clarita Valley parcels is early June, before the heat that arrives in June and stays through October. A homeowner who clears in April is early; a homeowner who clears in August is working in the worst heat of the year and is already past the date on the notice.

The practical calendar runs like this. February and March: cut and remove the previous season's growth while the soil still holds moisture and the work is easier. April: mow the grass down, clear the roof and the gutters, and take out anything dead within 30 feet. May: thin the shrubs in the 30 to 100 foot band, limb up trees to 6 feet above the ground, and move woodpiles and propane tanks out of the inner zone. June: the inspection. July through October: maintenance, because a cleared lot does not stay cleared.

What sequence does the work take on a slope lot?

On a graded lot the order matters more than the effort. The sequence that works is top down, and it starts with the roof.

1. Roof and gutters first. Remove needles, leaves and any dead material from the roof surface and the gutter line. A tile roof sheds fire well until the debris in the valley of the tiles catches.
2. The 30 foot zone second. Cut grass to 4 inches, remove dead shrubs, and pull mulch back from the stucco. A stucco wall resists flame, but the mulch bed against it does not.
3. The 30 to 100 foot band third. Thin shrubs to isolated clumps with space between them, remove the lower limbs of trees to 6 feet, and take out the dead material underneath. On a slope, the spacing is wider on the downhill side, because that is the direction fire travels.
4. The access and the address last. Keep the driveway clear to the street, keep the address visible from the road, and keep the gate hardware working. A crew that cannot find the house cannot defend it.

On a slope lot, the cut material has to leave the site or be chipped and spread in a thin layer. Piling it downhill of the house puts the fuel back in the path of the fire.

How does cleared ground change the way a fire behaves near a stucco house?

Cleared ground lowers the flame length and takes away the path. A grass fire in untreated fuel on a slope can throw flames 20 to 30 feet long; the same fire in grass cut to 4 inches with the dead material removed burns low and short, and a stucco wall with a tile roof will usually survive a low flame front that it would not survive a crown fire in the brush above it. The mechanism is simple: fire needs continuous fuel, and clearance breaks the continuity.

The second effect is embers. A home in the valley is more often lost to embers landing in a gutter, a vent or a woodpile than to a wall of flame reaching the wall. Clearing the roof, screening the vents and moving the woodpile out of the inner zone removes the places an ember can land and start a second fire after the flame front has passed. That is the part of the work that a homeowner can do without a crew, and it is the part that is checked on the inspection.

What does the inspection actually look for?

The inspector walks the property and checks the same items every year. Grass height, dead material on the ground, the spacing of shrubs, the limb height on trees, the condition of the roof and gutters, the location of woodpiles and propane tanks, and the visibility of the address. The notice that follows lists the deficiencies and a date to correct them. A homeowner who has kept the work on the February to June calendar usually passes without a second visit.

How is the work done on a lot too steep to mow?

A string trimmer and a hand crew, not a mower. On the steeper lots above Newhall and Saugus, a mower is unsafe and a tractor cannot hold the grade, so the work is done with trimmers, brush cutters and hand tools, and the cut material is raked and hauled. This is slower and it costs more per acre, which is why the work is scheduled in the cooler months. A homeowner who waits until June pays for the same job in heat that limits the crew to morning hours.

What changes after the first year?

Less than a homeowner expects. A cleared lot regrows. The grass comes back with the first rain, the shrubs send new growth from the crown, and the debris returns to the roof with the first wind. The second year is lighter than the first because the heavy fuel is already gone, but the maintenance window does not close. The work that keeps a house in the valley standing is the same work, done on the same calendar, every year.

Sources

• Los Angeles County Fire Department, brush clearance and defensible space standards: https://fire.lacounty.gov/brush-clearance/
• CAL FIRE, defensible space and home hardening: https://www.fire.ca.gov/dspace
• City of Santa Clarita, fire hazard and brush clearance information: https://www.santaclarita.gov/