Fire-Resistant Siding in Colorado: What Actually Survives a Wildfire

We burn-tested three common siding materials so you can see what actually happens under direct flame.

If you live along the Front Range or in the foothills, wildfire is no longer a once-in-a-generation worry. It is a planning reality. And while most homeowners think about defensible space and roofing, the siding on your home is one of the largest ignition surfaces it has. It is also one of the few things you get to choose.

So we did something simple. We took three common siding materials and exposed them to direct flame to see what actually happens. No marketing claims, just the test. Here is what we found, what the new Colorado wildfire code now requires, and how to think about your own home.

In this guide

1. What the test showed
2. Fire performance by siding material
3. The new Colorado Wildfire Resiliency Code, explained
4. Siding is one piece of home hardening, not the whole answer
5. Frequently asked questions
6. Talk to a Colorado siding contractor

What the test showed

We put three siding materials to the test under direct flame: vinyl, engineered wood, and James Hardie fiber cement. The results lined up with what the building science already tells us, and with what we see on real homes across Colorado.

Vinyl softened, warped, and melted. Vinyl siding is PVC, a plastic. It begins to soften at around 160 degrees and deforms and melts well before it would ignite. The problem with melting is not just cosmetic. When vinyl pulls away from the wall, it exposes the sheathing underneath, which is the part of your home you least want a fire to reach.

Engineered wood is treated, but it is still wood. Engineered wood siding like LP SmartSide is a legitimate, good-looking product, and it is treated for better performance. But it is a wood-based material, and wood-based materials are combustible. In a direct-flame situation, that distinction matters.

Fiber cement did not burn. James Hardie fiber cement is made from cement, sand, and cellulose fiber. It is non-combustible. It will not ignite when exposed to direct flame, and it does not contribute fuel to a fire. In the test, it held its shape and protected the wall behind it.

One honest note about the video. This is a controlled demonstration for education, not a prediction of how any specific wall assembly will perform in an actual wildfire. Real fire behavior depends on the whole structure. But the difference between a material that melts, a material that burns, and a material that does neither is real, and it is worth seeing.

Fire performance by siding material

James Hardie fiber cement siding

Non-combustible. James Hardie fiber cement carries a Class A fire rating with a flame spread index of 0 when tested in accordance with ASTM E-84, and it complies with ASTM E136 as a non-combustible cladding. In plain terms, it does not ignite and it does not feed a fire. One detail to keep accurate: the fire resistance is in the board itself. Applied paint can char under flame, and one-hour or two-hour fire ratings apply to a tested wall assembly, not to the siding by itself. For homeowners in wildfire-prone areas, non-combustible siding is not a marketing bullet point. It is a real risk-reduction decision.

LP SmartSide engineered wood siding

Treated, but combustible. LP SmartSide is a strong performer in other Colorado conditions, particularly impact and aesthetics, and it can be the right call for many homes. But for fire specifically, a treated wood-based product is not in the same category as a non-combustible one. If wildfire exposure is your deciding factor, that difference should weigh into the choice.

Vinyl siding

Combustible, and it melts. Vinyl has a place on budget-conscious projects in lower fire-risk areas. But in a fire zone it is the wrong tool for the job. It softens and melts under heat, which can expose the sheathing behind it, and it typically carries a lower fire rating than the other two materials.

The new Colorado Wildfire Resiliency Code, explained for homeowners

Colorado recently adopted its first statewide wildfire building code, the Colorado Wildfire Resiliency Code, often shortened to CWRC. It sets minimum construction standards for homes in designated Wildland-Urban Interface areas, usually called WUI zones, which are the places where neighborhoods meet open space, grassland, or forest.

Here is what matters for a homeowner. The code was adopted by the state's Wildfire Resiliency Code Board on July 1, 2025. Local jurisdictions in WUI areas are required to adopt it by April 1, 2026 and to begin enforcing it by July 1, 2026. In the Moderate and High Fire Intensity zones, the code calls for Class A rated exterior walls, which points homeowners toward non-combustible or ignition-resistant cladding. Significant additions or alterations, often cited at greater than 500 square feet, can also trigger compliance.

Siding is one piece of home hardening, not the whole answer

We want to be straight about this, because it is where some contractors oversell. Non-combustible siding meaningfully reduces one avenue of fire risk, but no single product makes a home safe from wildfire. Real home hardening is a system. It includes your roof covering, ember-resistant vents, gutters, decking, the glass in your windows, and defensible space around the structure. Siding is an important layer, and often the largest surface, but it works alongside the rest, not instead of it.

The honest way to think about it: choose the most fire-appropriate siding for your zone and budget, and pair it with the other hardening steps that fit your home. A good contractor will talk you through the whole picture, not just sell you the one product they happen to install.

Frequently asked questions

Talk to a Colorado siding contractor who will be straight with you

WestPro Home Exteriors is a James Hardie Elite Preferred Contractor and GAF Master Elite Roofing Contractor based in Longmont, serving Boulder, Denver, Fort Collins, Loveland, Estes Park, and the entire Front Range. If you are weighing your siding options, wondering what the new wildfire code means for your home, or just want a clear-eyed look at where your home stands, we offer a free inspection. We will tell you honestly what we see and what your options are, whether or not that ends in a project with us.