I,m about to plasterboard a room with 9ft high walls intending to dot and dab. Due to difficult access i will have to use 6x3ft boards which means walls are more than one board high. Will it be a problem to fix the top boards to the wall or will the adhesive have sufficient grab. Also how long does the adhesive take to set once applied to the wall and how long will i have to get the boards plumb and level. Any advice on how to keep the boards flat across the whole width of the wall as the brickwork is very old and uneven perhaps string line or something.