Guide to Wildfire Defense for California Residents
Updated: 3 days ago
Last reviewed/updated: September 2026
What's new in this update:
The new California Wildland-Urban Interface Code (in effect January 2026) and the updated fire hazard maps
Newer research, including lessons from the 2025 Los Angeles fires
Zone 0, synthetic turf, and what to do about trees
Insurance discounts and rebuilding incentives
Corrections to the deck, vent, roof and window advice
Notes on soil testing and utility programs for rebuilds
A free, printable Wildfire Home Checklist
With wildfires becoming increasingly frequent and severe, protecting your home and family is more important than ever. This article covers essential topics like home hardening, creating defensible space, and understanding the Wildland-Urban Interface (WUI) and Fire Hazard Severity Zones (FHSZ).
Our goal is to raise awareness and provide practical tips to enhance your home's wildfire resilience. Start learning how to fortify your home and surroundings against the threat of wildfires today.
Key subjects include:
Understanding these basics and taking action can significantly improve your home's chances of surviving a wildfire.
1 Understanding WUI and FHSZ
Wildfire defense is crucial in California for those living in the Wildland-Urban Interface (WUI), areas where human development meets wildlands. These zones are particularly vulnerable to wildfires, making awareness and preparation essential.
With wildfires becoming more frequent and destructive, we must understand some basic terminology, their designations, and what we can do to protect our property.
You may have seen homes remain intact while nearby homes were burnt to the ground after a wildfire. Significant research has recently been conducted to show proven effective methods for avoiding total loss, and we will introduce you to these methods in our next part, Wildfire Hardening Strategies.
Understanding the Wildland-Urban Interface (WUI) and Fire Hazard Severity Zones (FHSZ) is not just a matter of knowledge. It's a matter of safety. Knowing if your neighborhood and property are within these high-risk areas is crucial for your wildfire defense strategy.
Wildland-urban interface (WUI) refers to regions where homes and businesses are close to wildland vegetation, increasing the risk of wildfire exposure. Fire Hazard Severity Zones (FHSZ) refer to areas classified by the state based on their wildfire risk level. Since January 2026, new construction and most additions in a mapped Fire Hazard Severity Zone follow the California Wildland-Urban Interface Code (it replaced CBC Chapter 7A). In state responsibility areas(SRA), this now includes Moderate zones; in cities, it depends on what your city has adopted, so make sure you confirm with the building department before design starts.
The WUI and FHSZ maps are not static. Across the U.S., the wildland-urban interface grew by about a third between 1990 and 2020, and the number of homes in it by 46%, to roughly 44 million (Science, 2023). Nearly two-thirds of the homes lost were in grass and shrub fires, not forest fires. Look up your address on CAL FIRE's Fire Hazard Severity Zone Viewer, and check whether it is located in WUI. The maps get updated from time to time, and each city adopts them on its own schedule; ask your building department which map they are using.
2 Wildfire Defense: Home Hardening
A 2025 UC Berkeley study of about 47,000 structures in five major California fires found that hardening combined with defensible space could cut losses by about half; the spacing between buildings mattered most. An earlier USGS study of more than 40,000 structures (2013-2018) pointed to the same details: enclosed eaves, vent screens and multi-pane windows. The list below is in order of priority and effectiveness:
Maintenance: This is the most critical and important part of protecting against wildfire. Routinely inspect the roof, gutter, wall, and patio areas to avoid the collection of debris and dry leaves; keep branches off the roof and at least 10 feet from the chimney.
Roofing: Use a Class A roof: metal, clay or concrete tile, or Class A asphalt shingles. Some materials only reach Class A with a specific underlayment, so ask for the tested roof assembly as well as the shingle rating. Close the gaps at the ridge and eave edges; that is where embers slip under.
Vents: Embers get in through vents more than any other path. For new work in a hazard zone, vents need to be listed as flame- and ember-resistant (you can search the State Fire Marshal's listed products). For existing vents (attic, eave, soffit and crawl space), 1/16" to 1/8" metal mesh is a good start while you plan the upgrade.
Deck: Deck boards must be ignition-resistant or noncombustible in a fire-hazard zone; ask for the product listing before you buy. Add 6-inch metal flashing where the deck meets the wall, and keep the space under decks, porches and exterior stairs clear of firewood, lumber and anything stored.
Gutter: Use noncombustible materials such as aluminum, copper, or galvanized steel, and cover the gutter with a noncombustible leaf guard. Examine the roof edge and shield exposed wood materials with a metal drip edge.
Windows, skylights, and Doors: Use dual-pane windows with at least one tempered pane, skylights included. Check the frame too: in a 2026 fire test, vinyl frames sagged and often dropped the sash out of the opening; aluminum held up best, and fiberglass held unless it caught fire. Exterior doors should be noncombustible or solid-core wood (at least 1-3/4" thick). Seal the gap under every exterior door, including the garage door (weatherstripping or a noncombustible threshold); embers can blow in through a small gap.
Fences: Use non-combustible materials if within 5' (zone 0) of the building. Avoid design (plank on both sides) that can trap debris and embers. A 2026 UC Irvine study of about 100,000 CAL FIRE damage inspections (2013-2024) named wooden fences, along with flammable siding and open eaves and vents, as major contributors to building loss.
Eaves and Soffits: Cover with non-combustible materials to reduce vulnerability.
Sidings: Avoid vinyl, non-treated wood, or exterior insulation finish systems (EIFS) unless installed with a non-combustible base to make the wall assembly fire-resistant (similar to the roof assembly concept). At the bottom of the wall, use at least 6 inches of metal flashing or noncombustible material wherever it meets the ground, a deck, porch or balcony, or a lower roof; embers collect in those corners.
Many of these upgrades also count toward an insurance discount. Under California's Safer from Wildfires rules, insurers have to offer discounts for items like a Class A roof, ember- and fire-resistant vents, enclosed eaves, dual-pane windows and a 5-foot ember-resistant zone; ask your insurer which ones they recognize. The USGBC California guide estimates that going from the WUI code to IBHS Wildfire Prepared Home Plus, which can help with insurance, adds about $3,000; starting from the standard building code, about $15,000. Rebuilding after a disaster?¹ RISE Homes, a state program since April 2026, pays incentives for all-electric rebuilds of homes lost since 2017, with more for certified Passive House.² As a certified Passive House consultant and designer, this is work I do. Utilities have their own programs too.³
Before replacing your roof deck or any exterior building components, make sure you also check CalFire's home hardening tips and talk to your local Fire District about their requirements. For a full rebuild checklist, see USGBC California's 2026 Wildfire Rebuilding Guide.
I also put these items into a printable Wildfire Home Checklist, to walk around the house with; you can get it free here.
Photo Credit: Sandy Huffaker/Getty Images
3 What is Defensible Space?
Defensible space is the buffer created between your home and the wildland area that helps prevent the spread of wildfires. It is essential for protecting your property and ensuring the safety of your family and community. Defensible space is divided into zones, each with specific guidelines.
Zone 0 (0-5 feet), Ember-Resistant Zone:
Zone 0 (the first 5 feet around the house) matters most. Keep it free of anything that burns: bark mulch, firewood, a wood fence tied to the house. After the 2025 Los Angeles fires, IBHS found that homes with more than a quarter of this 5-foot zone covered in plants or mulch were damaged or destroyed about 90% of the time. Synthetic turf has become popular, but it is plastic (it melts and can burn right next to the wall); the state rules do not address it yet, so I would keep it out of the first 5 feet.⁴ Gravel or pavers work well, and a metal gate where the fence meets the wall. Keep branches trimmed 10 feet away from chimneys and stovepipes.
About plants: this does not mean a bare yard. Low, green, watered plants (lawn, ground cover, small flowering plants) are fine if they are spaced out and kept back from windows, doors and vents; what should go are woody shrubs and hedges against the wall, juniper especially. Healthy trees next to the house can usually stay with pruning (see the trees section below). The state's own Zone 0 rules were approved in August 2026 but are still under state review, so they are not in effect yet.
Zone 1 (5-30 feet), Home Protection Zone:
Remove dead plants, trees, and combustible materials. Pick plants that stay green with little water, and keep them spaced and trimmed; how you maintain a plant matters more than where it comes from. Keep tree branches off the roof and at least 10 feet from the chimney, and prune to keep about 10 feet between tree canopies. Prune flammable plants and shrubs near windows and remove them from under decks, balconies, and stairs. Keep plants high in oil or resin, like juniper, pine and eucalyptus, away from the house. Palms catch embers easily; cut off the dead fronds every year.
Zone 2 (30-100 feet), Reduced fuel/Thinning Zone:
To reduce the spread of fire, create vertical and horizontal space between trees and shrubs. CAL FIRE's guideline: on flat ground, shrubs apart by twice their height and tree canopies 10 feet apart, more on a slope; from the top of a shrub to the lowest branch above it, 3 times the shrub's height. Use fire-resistant landscaping. Regularly mow grass and create breaks in vegetation to slow down fire. Distance to the neighbor matters too; in the 2018 Camp Fire, homes more than about 60 feet from a house that burned survived at a much higher rate (Fire Ecology, 2021). Worth thinking about when placing an ADU or an addition.
What about trees?
After the 2025 Los Angeles fires, many people asked whether to cut down the trees near their homes. Researchers mapping the Eaton Fire found tree damage mostly came from burning houses, not the other way around; many trees were burned on the side facing a lost home and still green on the street side. A Forest Service study of the Thomas and Camp fires found homes near well-watered trees survived more often.
Oaks are a good example. Coast live oak has the thickest bark of our native oaks and can resprout after a fire; the 2026 USGBC California rebuilding guide recommends keeping fire-resistant native trees such as some oaks.
When I volunteered with the cleanup in Santa Rosa in 2017, locals told me that many of the old oaks had come through the fire; they grew up with fire in this landscape. I see too many healthy old trees removed in my neighborhood.
This doesn't mean any tree, anywhere. No new trees in the first 5 feet; keep the canopy off the roof and 10 feet from chimneys; trim lower branches 6 to 10 feet up; and avoid oily species like eucalyptus. After a fire, wait a full growing season and have an arborist look before removing a mature tree.
The extension of defensible space can be applied to tasks such as maintaining emergency access for fire trucks and trimming overhanging vegetation to allow passage for emergency vehicles. Check with your local fire department to learn more about their specific requirements.
Many have installed sprinkler systems on their roofs and yards, but they should cover all areas where embers will land and keep the area wet. The system's performance depends very much on wind, radiant heat, and water availability, so this should be "supplemental" and not the primary method for wildfire mitigation.
A simple upkeep routine
Weekly: clear dead leaves and debris from the first 5 feet, and clean the gutters and roof.
1 to 4 times a year: seal gaps over 1/8" in siding and around eaves, and check the weatherstripping on the garage door.
Yearly: prune lower branches at least 6 feet up (1/3 of the height on small trees), and keep branches 10 feet from chimneys.
When it's time to replace: Class A roof, noncombustible siding and deck, dual-pane tempered windows.
Adapted from the USGBC California 2026 Wildfire Rebuilding Guide.⁵
The Wildfire Home Checklist has all three zones, this upkeep calendar and the insurance items on four printable pages. Get the checklist
For more information on defensible space, please check CalFire's and NFPA's website.
Fire readiness is easiest to build in when you are already planning work: a remodel, an ADU, a new roof or windows, or buying a home in a hazard zone. If that is you, book a 15-minute call. For a property you are serious about, my feasibility study covers the fire zone, code path and hardening scope before you commit. You can also get my ADU guide here.
Image Source: NFPA
Notes
1. Soil testing after a fire. Ash and debris can leave heavy metals and other chemicals in the soil, and smoke and lead contamination was found up to 7 miles from the 2025 Los Angeles fires. The only way to know is a lab test; results can take up to 3 months. Test before or during construction, and have any cleanup done by a licensed contractor with hazardous-materials training. The USGBC California rebuilding guide lists testing resources, and the EPA has more.
2. For houses and ADUs, the RISE Homes Passive House incentive requires a certified Passive House. RISE covers homes lost in a declared disaster since 2017.
3. For the Los Angeles rebuilds: LADWP's HOME LA program for all-electric rebuilds, SCE's SWITCH program for customers in the Eaton and Palisades areas, and Clean Power Alliance's battery rebate ($2,000 base, up to $3,500). Programs change, so check with your own utility.
4. The USGBC California 2026 rebuilding guide also says to avoid artificial turf around the house.
5. The full USGBC California upkeep table also covers bird stops on tile and metal roofs, 6-inch metal flashing where a deck meets the wall, and a spark arrestor on the chimney (3/8 to 1/2 inch mesh).
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