NWCB Technical Library

Gypsum Drying Conditions — Field Guide provides drywall contractors with a practical framework for assessing jobsite drying readiness using dew point spread (ΔT) — the difference between gypsum surface temperature and dew point — rather than air temperature alone. The guide challenges the common "50°F and rising" standard, demonstrating that identical temperatures can yield vastly different drying performance depending on relative humidity. Drawing on industry data from NWCB, DWFC, USG, and GA-236, it presents drying zone tables, a contractor decision guide, and field measurement instructions. The recommended target is a 15–25°F dew point spread for reliable joint compound drying. Coverage includes ideal conditions (70°F/40% RH), IR thermometer use, example calculations, and guidance on temporary desiccant climate control systems.