An Assessment of Suspect Drywall Damage from Flooding

In the US, drywall (gypsum board) has long replaced plaster as the major wall material in buildings, with a need for fire resistance, some structural strength, and acceptance of coatings (finishes). The manufacture of drywall has changed significantly since the patent by August Sackett in 1894. One of these is the reduction of the weight for regular non-type X board while maintaining flexural strength, limiting nail pull, and fire resistance. After a flood, a building owner expressed concern over the potential alteration of the structural character of the drywall and its impact on operating properties. To complicate the situation, holes were bored into the drywall to rapidly dry the wallboard in order to prevent mold growth. As part of the investigation, a number of test were conducted. These included measuring moisture content in cores, determination of composition of the drywall samples and control materials, assessment of mechanical characteristics of the field and control samples, evaluation of thermal characteristics by IR thermography, and evaluation of water staining by UV lighting. Mechanical testing included flexural strength determination, nail pull testing, edge hardness testing, compressive strength testing. Field samples from water level (WL) and above water level (AWL) were tested for all tests. Field samples with and without holes were tested for flexural strength determination. Comparable controls with and without holes were tested for flexural strength determination. Controls with holes and standard aesthetic repairs were also tested for flexural strength determination. The results revealed a generally resilient wallboard after flooding.