Structure hardening guide
Hardened homes: how structures survive wildfire
A hardened structure is built and maintained to resist the three ways wildfire destroys buildings: flying embers, radiant heat, and direct flame contact. This guide walks through each layer of hardening, then explains the role external shielding plays in a complete defense plan.
Why hardening works
Most structures lost in wildfires are not overrun by a wall of flame. They ignite from embers that can travel a mile or more ahead of the fire front, landing on roofs, in gutters, at the base of walls, and inside vents. Research from the Insurance Institute for Business and Home Safety and the US Forest Service shows that addressing these ignition points dramatically improves survival odds.
No single upgrade is enough. Hardening is a system of layers, and each layer covers the weaknesses of the others.
The standard layers
The six layers of structure hardening
Non-combustible roofing
The roof is the largest ember-catchment surface on most structures. Class A fire-rated roofing (asphalt composition, metal, tile, or slate) resists ignition from ember showers. Keep gutters and roof valleys clear of needles and leaves, which ignite readily and carry fire to the roof edge.
Ember-resistant vents
Attic, crawl space, and foundation vents are a direct path for embers into the structure. Vents rated to resist ember entry (fine corrosion-resistant mesh or baffled designs approved under Chapter 7A of the California Building Code) block embers while preserving airflow.
Ignition-resistant siding and decks
Non-combustible or ignition-resistant siding (fiber cement, stucco, metal, or treated wood) limits flame spread up exterior walls. Enclose the undersides of decks and balconies, and keep the first five feet around the structure free of combustible material, including mulch and stored items.
Multi-pane tempered windows
Windows fail from radiant heat before flames arrive, letting embers and fire inside. Dual-pane windows with at least one tempered layer withstand far more heat than single-pane glass. Metal screens and non-combustible shutters add another barrier.
Sealed gaps and openings
Embers exploit openings as small as an eighth of an inch: under doors, at garage door seals, around eaves, and at roof flashings. Weatherstripping, caulking, and ember-resistant flashing close the pathways that let embers lodge and smolder.
Defensible space
Hardening works together with the landscape. Clearing combustible vegetation and materials in zones around the structure reduces flame contact and limits the radiant heat the structure must survive.
The external shielding layer
Where FireFoil fits in a hardened structure plan
Even a well-hardened structure has surfaces that remain exposed when a fire arrives: the roof plane, window glass, and wall assemblies facing the fire. FireFoil™ wildfire structure shields add a physical barrier over those surfaces, reflecting the majority of radiant heat and stopping embers before they can lodge against the structure. The shielding technology has been used by the US Forest Service to protect structures and monuments for decades.
FireFoil is not a replacement for hardening. It is the layer that works when the fire is at the property line and there is no time left for retrofitting: a passive barrier that needs no water, electricity, or chemicals, deployed before evacuation. Shields come in pre-fabricated widths of 5, 10, 15, and 20 feet, so a crew can cover a base perimeter fast or wrap a complete structure for maximum protection.
See the deployment options and the research behind the technology for the field data supporting this layered approach.
A complete defense plan, in order
- Harden the structure: roof, vents, siding, windows, and sealed gaps.
- Maintain defensible space in zones around the structure.
- Monitor fire conditions and official alerts through the season.
- Deploy FireFoil shielding over exposed surfaces before evacuating.
- Evacuate early. No structure protection is worth delaying evacuation.
Complete Your Plan
Add the shielding layer to your hardened structure
FireFoil shields are available through authorized distributors. Find the right starting point for your structure.