In the event of water build-up due to improper drainage, which of the following is least likely to occur?

In scenarios involving water build-up due to inadequate drainage, the option relating to a sudden change in the slope and strength of the deck is least likely to occur. While prolonged exposure to water can certainly weaken materials and lead to structural issues, a sudden change would generally not be a direct result of water build-up itself. Typically, structural changes manifest over time due to sustained damage rather than an instantaneous effect.

On the other hand, increased interior humidity, structural water damage, and mold growth are direct consequences of water accumulation. Prolonged conditions of excess moisture can lead to immediate increases in humidity levels within a space, which can then cause various forms of water damage to the structure. Additionally, stagnant water and moist environments are conducive to mold growth, potentially leading to health hazards. Therefore, while water accumulation is detrimental to roofing and structures, it is more likely to lead to gradual degradation and moisture-related problems rather than a sudden change in structural integrity.