Home hardening

Understanding how homes catch fire in wildfires can help you understand changes you can make to your home to make it less likely to be destroyed. The Insurance Institute for Business & Home Safety built a large test chamber it uses to simulate ember storms attacking homes during wildfires, and ran tests to learn the vulnerable points on a home.

Watch the institute's video below to learn about weak points to look for in your home's construction, and use information on this page and linked to from it to harden your home to make it less likely to burn in a wildfire. Most homes with good defensible space that burn in wildfires are ignited by flying embers rather than a flame front. Burning embers move like a swarm of bees and can find any weak spot to start your home burning, which can then spread to consume it entirely.

Building a new home in California? Refer to the State Building Codes:

​Chapter 7A [SFM] Materials and Construction Methods for Exterior Wildfire Exposure

• ​Vents
  
• Gutters
  
• Roofs
  
• Decks
  
• Siding
  

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Vents with 1/4 inch mesh screen can create an opening for embers to enter the home. This puts the structure at high risk of ignition. Cover all vent openings with 1/16 in - 1/8 in metal mesh ​(fiber glass or plastic mesh will melt). 

Or, consider vents specifically designed to prevent embers from entering the home by closing vent openings when exposed to heat. You can find a listing of such vents recommended by the State Fire Marshal's office by searching for Category 8165--Vents for Wildland Urban Interface on this web page.
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For more, check out:
Vulnerability of Vents to Wind-Blown Embers (credit, Fire Safe Marin).

Clean any leaves and debris that accumulate out of rain gutters. This material is highly combustible and can cause the structure to ignite. In areas subject to wildfire, metal gutters are recommended over plastic or vinyl. 

Gutter guards or covers can also be installed to reduce the accumulation of debris; however, foam or plastic gutter guard inserts can be flammable so are not recommended. 

If not made of the proper material, your roof could be the most vulnerable part of your home. Roof coverings have multiple fire ratings, and Class A is the highest / most fire-resistant option. Class A roof coverings are made from fire-resistant materials such as asphalt fiberglass composition shingles, and concrete or clay tiles. Unrated roofs are often untreated wood shake and should be replaced with a Class A roof in areas of high wildfire risk.

You can find a list of all non-wood roof coverings listed by the State Fire Marshal's office for use in areas subject to wildfires by searching for Category 8180—Non-Wood Roof Coverings/Assemblies for Wildland Urban Interface on this page.

It is also important to regularly clean all combustible materials such as leaves and debris off the roof. 

On Red-Flag Warning days, or when evacuating, remove all combustible items such as furniture, grills, or propane tanks off the deck and away from the home. Do not store any combustible materials under the deck and make sure to regularly clean any leaves and debris from the area. 

The materials used to build the deck also determine its level of vulnerability to wildfire. You can find decking materials recommended by the State Fire Marshal's office by searching for Category 8110--Decking for Wildland Urban Interface on this page.

mbustible siding like wood shingles, wood or vinyl lap-joint, or plywood can catch fire during a wildfire and lead to loss of your home and other structures.

Non-combustible sidings are cement-based materials such as stucco, stone veneer, and Hardy Plank or Hardy Panel.

You can find fire resistant siding recommended by the State Fire Marshal's office by searching for Category 8140 -- Exterior Wall Siding and Sheathing for Wildland Urban Interface on this page.

Replacing siding or covering it can be costly, but will likely cost less than replacing your entire home, its furnishings, and belongings.

Make sure the bottom six inches of your exterior walls are non-flammable material (burning embers blow like snow and drifts can pile up against the bottom of walls, like hot coals from a barbecue against your structure).

You can find a list of all building materials listed by the State Fire Marshal's office for use in areas subject to wildfires using this link.

If your property is within a Design Control District (D District) you may be faced with regulatory requirements that make it difficult to harden your home to prepare for wildfires, for example by replacing your flammable wood shake roof with a Class A rated asphalt shingle or tile roof, or replacing your wood siding with fire resistant cement fiberboard or stucco siding.

County ordinances for D District areas in inland portions of the County are here.

County ordinances for D District areas in the Coastal Zone are here.

MORE RESOURCES

Wildfire Home Retrofit Guide
Low-Cost Retrofit List
Home Hardening - Wildfire Risk to Communities
​Defensible Space Self-Assessment​