Gypsum board (drywall) is identified in the WRT body of knowledge as highly vulnerable to moisture exposure, yet capable of recovering strength when dried—provided it has not sustained irreversible primary damage. The WRT manual explains that gypsum wallboard is among the most moisture-sensitive common building materials, showing rapid and dramatic change with elevated moisture levels. However, it also states that gypsum has a greater ability to recover than many other engineered products.

Critically, the WRT guidance distinguishes between primary damage (immediate structural failure) and recoverable wetting. For example, overhead or horizontally installed gypsum that becomes wet can lose structural integrity, sag, and create a significant safety concern; this sagging is considered permanent damage and requires removal.

In contrast, when gypsum board installed vertically on walls is wet but has not experienced primary damage (e.g., not structurally compromised, not severely deteriorated, and appropriate contamination considerations are addressed), the WRT manual notes that it can restore: during the drying process, gypsum’s original strength is restored, and after drying it may even be slightly stronger (though sometimes more brittle). This recovery characteristic is what makes gypsum board the best match to the question’s description—losing structural integrity when wet yet regaining strength when properly dried.

This material behavior is central to WRT decision-making: whether to dry in place, perform limited disruption (e.g., baseboard removal and cavity airflow), or remove materials for safety/health reasons. The WRT body of knowledge treats gypsum as potentially restorable depending on installation orientation, degree of damage, and contamination risk, which is why it is specifically described as losing integrity when wet and regaining strength when dry.

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