Partition Walls and Their Restraining Effect on Warp in Built-In Wall Studs

The focus is on understanding the behavior of walls with regard to the propensity of studs to warp at different moisture content. Experimental tests on whole wall structures were conducted. The walls were built up using studs of Norway spruce (Picea abies) and cladding made of gypsum wallboard. The tests were performed simulating in-service conditions, i.e., about 35% relative humidity and a temperature of 22°C. Tests were conducted with double- and single-sided cladding. Twist and crook were measured on the studs continuously during the tests. The warp of the studs was also measured before and after each test. The double-sided cladding reduced the twist in the studs significantly, by about 75% when compared with twist developed in the same studs when vertically suspended without restraint. The single-sided cladding only slightly reduced the twist, by about 13%, but increased the crook substantially. The value for crook for single-sided cladding was more than double and had reached more than half its final value in less than a week.