Green boards are manufactured with a paper covering that is waterproof or water-resistant. It's flexible, unlike blue board. It is built in the shape of tiles and cut to size, just like other types of drywall sheets. Greenboard can be used by itself within a room without the need for any additional cladding except at floor level. However, it's also normally installed with plaster or render. Wet or damp applications could never be used with the blue board as the water may cause the gypsum to swell and the board may eventually disintegrate.