Hi. I am partitioning off my garage to make a small workshop room. I intend using 4x2 studing and plasterboard for the walls and plasterboard to the original beams forming the ceiling. I would like to know if it is ok to use one layer of plasterboard on each side of the studding and one layer on the ceiling or do I need two layers to form an adequate fire barrier? The ceiling and walls will be insulated with the appropriate lagging.