Thermal and Heat Damage from Nearby Wildfires

Your home did not burn down. The fire came close — maybe it burned the house next door, or it stopped at the edge of your property — but your structure is still standing. The insurance company sends an adjuster who does a quick walk-around and says there is minimal damage. Maybe they pay for some exterior smoke cleaning and call it done.

But extreme radiant heat from a nearby wildfire can cause extensive damage to a structure without any direct flame contact. Much of this damage is hidden — it is inside walls, behind siding, underneath roofing materials, and in components you cannot see without destructive testing. If no one looks for it, it does not get found. And if it does not get found, it does not get paid.

What Heat Damage Looks Like

Heat damage from a nearby wildfire is often uneven — concentrated on the elevations (sides of the house) that faced the fire and diminishing on the sides that were shielded. This directional pattern is itself evidence of fire exposure. Common heat damage includes:

Siding and Exterior

• Vinyl siding:Warps, buckles, or melts at relatively low temperatures (165–220°F). Even siding that appears intact may have lost its shape or become brittle.
• Stucco:May develop hairline cracks from thermal stress. The galvanized wire lath behind the stucco can lose its protective zinc coating and tensile strength from heat exposure (zinc volatilizes above approximately 787°F).
• Wood siding: Charring, discoloration, or checking (small surface cracks) on the fire-facing side. Wood may also dry out and become more vulnerable to future moisture problems.
• Composite decking: Warps or melts. If your composite deck shows heat damage, that is evidence that other materials on the same elevation were exposed to similar temperatures — which may mean vinyl window seals, flashing, and other components on that side are also compromised.
• Paint: Blistering, peeling, or discoloration on the fire-facing elevations.

Windows and Doors

• Dual-pane window seal failure: Heat can compromise the thermal seal between dual-pane glass. The window may look fine initially but develop fogging or condensation between the panes weeks or months later as the broken seal allows moisture in.
• Vinyl window frames: Warping or distortion. Even slight warping can prevent proper operation and compromise the weather seal.
• Weather stripping: Heat degrades rubber and foam weather stripping on doors and windows, reducing their thermal and moisture performance.

Roofing

• Asphalt shingles: Extreme heat accelerates granule loss, causes premature aging of the asphalt, and can melt or deform shingles. The damage may not be visible from the ground.
• Roofing underlayment: The felt or synthetic underlayment beneath the shingles can degrade from heat, losing its waterproofing properties. This damage is completely hidden — you cannot see it without removing the shingles.
• Flashing and sealants: Heat can cause sealants to fail and flashing to lose its adhesion or shape.

Behind the Walls

• Electrical wiring:Wire insulation (typically rated to 140–194°F depending on type) can degrade from heat exposure, creating a hidden fire risk. The wire may function normally at first but fail under load later.
• Plumbing: PVC and CPVC pipes inside walls facing the fire can soften, warp, or lose structural integrity from heat conducted through the exterior wall.
• Insulation: Fiberglass insulation is heat-resistant, but the kraft paper facing can char. Foam insulation (spray foam, rigid board) can melt or off-gas.
• HVAC components: Exterior condenser units, refrigerant lines, and ductwork in attics or crawl spaces can be damaged by radiant heat.

Concrete and Masonry

• Concrete: At extreme temperatures, concrete can spall (surface layer flakes off), crack, or lose structural strength. Foundation walls, retaining walls, and concrete patios facing the fire may be affected.
• Mortar joints: Heat can degrade mortar between bricks or blocks, even if the bricks themselves appear undamaged.

Why the Insurance Company Misses It

Heat damage goes undetected for several reasons:

• Visual inspection is not enough. A carrier adjuster doing a walk-around may see a house that looks intact and conclude there is minimal damage. Many forms of heat damage are behind surfaces and require destructive testing to discover.
• Delayed manifestation. Some heat damage — particularly window seal failure and wiring degradation — does not become apparent until weeks or months after the event.
• Focus on homes that burned. After a wildfire, insurance resources are concentrated on total losses. Homes that survived are given less attention, and their claims are processed quickly with minimal inspection.

How to Document and Prove Heat Damage

1. Consider hiring a structural engineer.A licensed structural engineer can perform a thermal damage assessment, examining the fire-facing elevations, identifying materials exposed to heat, and determining what testing is needed. California structural engineering rates typically run $150–$300 per hour, and a detailed report may cost several thousand dollars — but it is often the foundation of a thermal-damage claim.
2. Use comparative evidence.If composite decking on the fire-facing side of the house deformed or softened (composite materials typically deform in the 170–200°F range), that is evidence that vinyl window components on the same elevation (similar softening range) were also exposed to damaging temperatures. The inference is elevation-specific and depends on actual exposure geometry (orientation, shielding, wind, distance to the flame front). One visible form of damage supports the inference of hidden damage to materials with similar or lower heat tolerances on the same elevation.
3. Request destructive testing. In some cases, siding must be removed to inspect wiring, insulation, and sheathing behind it. Shingles may need to be lifted to inspect underlayment. The cost of testing is a legitimate claim expense.
4. Document the directional pattern. Photograph all four elevations. The damage pattern should correspond to the direction of the fire — heaviest on the fire-facing sides, lightest on the shielded sides. This pattern proves the damage is from the fire, not from pre-existing conditions.
5. Monitor for delayed damage. Check windows for fogging between panes over the following months. Test electrical circuits under load. Watch for new leaks or moisture problems. Report any delayed-onset damage to your insurer promptly as a supplemental claim.

This article is for informational purposes only and does not constitute legal advice. Insurance policies and applicable law vary by state and by policy form. Consult with a licensed professional regarding your specific situation.

Written by Leland Coontz III, Licensed Public Adjuster, CA License #2B53445.