sorry for sounding thick but let me get this right?you can just spray it on any plasterboard then fire it up against any form of background that the new plasterboard is going on...i.e.bare brickwork,old plastered walls,etc etcchurch said:Not sure how much a can , but some loft converters and builders i work for have started using it , don't think they has mastered it yet tho : . The main problem Seems to be it pushes the joints out of line while foam is setting/expanding but they hate mixing the board adhesive so they will try anything.