Class A fire-rated assemblies over steel
What a Class A rating means and what goes into a fire-hardened wall and roof over steel.
Read →Ember-resistant detailing for WUI homes.
Wildfires take most homes through wind-blown embers that lodge in exterior details, not a passing wall of flame. Here are the vents, eaves, edges, and openings that matter, and how they pair with a non-combustible steel frame.
In most wildland-urban-interface losses, a home is set alight not by a passing front of flame but by wind-blown embers that land on and lodge in vulnerable exterior details. Ember-resistant detailing closes the paths embers use to enter or settle on a home: vents, eaves, roof edges, decks, and gaps around openings. Paired with a non-combustible light gauge steel frame, that detailing tackles the way homes are most often lost in California wildfires.
Why do embers matter more than flames?
In a major wildfire, wind carries burning embers well ahead of the fire front, sometimes for more than a mile. Those embers rain onto neighborhoods, collect in vulnerable spots, and smolder until they ignite something combustible. This is why homes far from the visible flame front still burn. Hardening a home against embers therefore targets the actual failure mode rather than only the dramatic one.
Closing the paths embers use to enter a home is one of the highest-value, lowest-drama ways to improve its odds in a wildfire.
What are the key ember-resistant details?
The specifics are set by your designer and by Chapter 7A for your parcel, but the details that matter most are consistent:
- Ember- and flame-resistant vents that keep burning embers out of the attic and crawl space.
- A Class A roof assembly with sealed edges and bird-stops at tile or metal profiles.
- Enclosed or protected eaves and soffits so embers cannot lodge and ignite.
- Non-combustible cladding, and non-combustible or ignition-resistant decking.
- A non-combustible zone immediately around the home, kept clear of fuel.
- Sealed gaps around windows, doors, pipes, and other penetrations.
- Dual-pane tempered glazing that resists radiant-heat failure.
How does light gauge steel help?
A non-combustible light gauge steel frame removes the structure itself from the fuel chain, so even if embers reach the framing cavity the frame will not ignite or carry fire. Ember-resistant detailing then closes the exterior paths embers use. The two work together: the frame addresses the structure, the detailing addresses the openings, and neither replaces the other.
What does Chapter 7A require for these details?
California Building Code Chapter 7A sets ignition-resistant standards for exteriors in wildland-urban-interface zones, including requirements for vents, roofs, eaves, exterior walls, decking, and glazing. Vents in particular are commonly required to resist ember and flame intrusion, with products tested to standards such as ASTM E2886. Because these requirements are exterior-assembly driven, they align naturally with building the structure in non-combustible steel. For more, see non-combustible steel framing for California fire zones.
How does Cal Steel build for ember resistance?
Cal Steel engineers each home in Vertex BD with AutoCAD and Revit BIM and fabricates non-combustible light gauge steel in its Van Nuys facility, with additional manufacturing in Tecate. As a Los Angeles City Approved fabricator and erector certified to ICC-ES ESR-4905, Cal Steel delivers a non-combustible frame designed to carry the Chapter 7A ember-resistant assemblies a WUI project requires, and can extend the approach into modular volumetric homes and heavier structural steel where a site demands it.
Frequently asked questions
Why do embers matter more than flames in a wildfire?
Most homes lost in WUI fires are ignited by wind-driven embers that travel ahead of the fire, land on or enter the home, and smolder into ignition, not by a wall of flame. Closing the paths embers use is one of the highest-value ways to harden a home.
What are the most important ember-resistant details?
Ember- and flame-resistant vents, a Class A roof with sealed edges, enclosed or protected eaves and soffits, non-combustible cladding and decking, a non-combustible zone next to the home, sealed gaps around openings, and dual-pane tempered windows.
Does a steel frame remove the need for ember-resistant detailing?
No. A non-combustible steel frame removes the structure from the fuel chain, but embers ignite homes through vents, decks, and combustible exterior components. A hardened home needs both the non-combustible frame and the ember-resistant detailing.
For more answers across light gauge steel, structural steel, and modular, see the Cal Steel FAQ.
Go deeper
Fire & code
Fire & code
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