Water-resistant gypsum backing board (see ASTM
C 1396/C 1396M, Standard Specification for Gypsum Board),
commonly called “green board” because of the color of its
face paper, is specially designed and formulated to serve as
a base for ceramic and similar tile in areas subject to occasional
water or moisture such as tub and shower enclosures,
kitchens, and utility rooms. The core, face paper, and back
paper are formulated and manufactured to resist the effects of
moisture and humidity.