A common safety issue found during a deck inspection is a lack of _____.

The correct answer is the lack of guardrail infill. Guardrail infill is a crucial safety feature designed to prevent people, particularly children, from falling through the spaces between the rails of a guardrail. When inspecting a deck, it is essential to verify that guardrails are not only in place but also properly infilled to provide adequate protection. If the guardrails have large gaps or spaces, they can pose a significant safety hazard.

While handrails and footings also play vital roles in deck safety and structural integrity, the absence of suitable guardrail infill specifically addresses the risk of falls, making it a frequent focus during safety inspections. Insulation, on the other hand, is typically not relevant to deck safety concerns, as it relates more to thermal efficiency within buildings rather than structural safety of outdoor features like decks. Therefore, the focus should be on ensuring that guardrail infill is present and effective during inspections.