Is Composite Fencing Fire-Resistant? Class A and WUI Zones
What ASTM E84 Class A actually means, where the rating is required by code, and why composite outperforms wood in wildfire-hazard areas.
· 5 min read · By Compoxen Editorial
Yes. Compoxen composite fencing carries a Class A fire rating, the highest classification under ASTM E84 surface burning characteristics testing.
What Class A means
ASTM E84 measures two things: flame spread and smoke development. Class A is the highest rating, awarded to materials that score 0–25 on flame spread and 0–450 on smoke development. Class B and Class C are progressively less restrictive.
Where it matters
Many California jurisdictions require Class A exterior materials in WUI (wildland-urban interface) zones. Colorado and Idaho mountain communities are increasingly adopting similar requirements. Insurance carriers in fire-hazard areas often quote lower premiums for properties with non-combustible exterior materials including fencing.
How composite achieves Class A
Mineral filler is non-combustible. A composite board with a high mineral content has substantially lower flame spread than a wood board of the same thickness. Compoxen formulates the polymer matrix specifically to maintain Class A performance under the ASTM test conditions.
What untreated wood scores
Untreated cedar and pine are combustible by category. Pressure-treated wood with fire-retardant chemistry can achieve Class B or Class C, but the chemistry leaches over time. Composite holds its Class A rating for the life of the fence.
What this means for a homeowner
If you are within 500 feet of vegetation that burns, ask your insurance carrier and your local fire authority whether Class A fencing is required or rewarded. In many California zip codes the answer is yes.
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