The 1/2-inch lag screws attaching the structural steel ledger require fire protection, making option D correct. These fasteners are structural components of the ledger-to-CLT connection and therefore form part of the connection whose fire performance must be maintained for the required duration.

AWC Technical Report 10 states that wood structural connections—including their connectors, fasteners, and participating members—must be protected from fire exposure for the required fire-resistance time . Protection may be provided by wood cover, fire-rated gypsum board, other approved materials, or a combination.

TR10 distinguishes structural connection fasteners from small fasteners used merely to hold sacrificial protection in place. The report specifically explains that fasteners attaching protective wood strips need not themselves be protected, provided they are sufficiently long to keep the protection in position throughout the required exposure.

In the illustrated ledger connection, the 1/2-inch lag screws transfer structural load between the steel ledger and CLT wall. Their thermal protection is therefore integral to maintaining connection capacity.

References/Topics: AWC Technical Report No. 10 Sections 4.5 and connection examples; thermal protection of structural connectors and fasteners.

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