Question:

• Should we use 9.5mm or 12.7mm thick moisture resistant gypsum plasterboard cut to gypsum ceiling panels for laid-in exposed grid ceiling system of rectangular pattern 600mm x 1200mm or 610mm x 1220mm in wet areas ?

   

Answer:

• Moisture resistant gypsum plasterboards (also called green gypsum plasterboards), if manufactured and tested under laboratory conditions to meet strictly relevant standards of USA, Canada, UK, France, Germany, Australian, New Zealand, will have good moisture resistance property and are able to perform safely in the working environment up to 95% RH (RH = relative humidity) and 38⁰C. Put it simple, under the adverse effects of high moisture and temperature, the gypsum core is not crumbly and there is no delamination of paper liner from the gypsum core. Neverthless, at such a high moist ambience, all green gypsum plasterboards do not possess good anti-sagging property for a long working time. As a result, moisture resistant plasterboard, be it 9.5mm thick or 12.7mm thick, should not be used to process into gypsum ceiling panels for laid-in exposed grid ceiling with rectangular pattern 600mm x 1200mm or 610mm x 1220mm in wet areas.

   

• It is best to use permanent water resistant calcium silicate boards / autoclaved cellulose fiber reinforced cement boards of minimum 6mm thickness, with surface finished with high quality acrylic paint or laminated with PVC film, to process to ceiling panels for 600mm x 1200mm or 610mm x 1220mm exposed grid ceiling in wet areas.