I'm remodelling the bathroom (smallish 2m x 1.7) as a wetroom. I'm replacing the whole floor: 24mm ply, 6mm tile backer board, electrical underfloor heating, self levelling stuff, 10mm porcelain tiles (300x 600). I may be able to lay the whole ply board (apart from the tray former) as one piece. Is there an advantage in having the ply substrate as one piece? Or as few pieces as possible? Or , indeed any disadvantages? I'm imagining that one piece would prevent the problems of movement between boards.