Evaluation of fire damage far exceeds the Standards of Practice (SOPs) and should be left to professionals. However, you can at least explain the limitations regarding fire damage if you have some knowledge. These two publications can provide you with some information.
Post-Fire Assessment of structural Wood Members
Evaluation of dimensional lumber will be different from that of timbers and glulams. The two categories reflect different assumptions that need to be made during assessment. Most inspectors will be dealing with dimensional lumber, often roof framing in attics.
The severity of damage to wood framing in an attic fire depends mainly on how hot the fire gets, how long the members are exposed, and how the wood was protected and detailed.
Fire intensity and duration
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Peak temperature and heat flux govern charring depth and loss of cross‑section; higher temperatures and longer exposure cause deeper char and greater strength loss.
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Attic fires often burn intensely and undetected for some time, allowing prolonged exposure that can severely weaken joists, trusses, and plates.
Member size, species, and moisture
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Thicker, dense hardwoods char more slowly than thin, low‑density softwoods; heavier‑section members tend to retain more strength at a given char depth.
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Higher moisture content can slightly slow charring but also prolongs the time the wood spends at elevated temperatures, affecting residual strength.
Protection and detailing
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Drywall, sheathing, insulation, and other coverings delay heat transfer and reduce the exposed area, limiting charring and damage.
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Unprotected trusses, open webs, gusset‑plate connections, or closely spaced members can allow flames to circulate inside the framing, increasing burn‑through and connection failure.
Post‑fire exposure and assessment
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Cooling rates and residual moisture (e.g., from firefighting water) can influence checks, warping, and long‑term degradation even after the fire is out.
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In practice, many guidelines treat deeply charred sections (roughly ¼ in / 6 mm or more) as needing replacement or structural review, regardless of the exact fire duration.