bathroom plywood floor in one piece?

[ahearsum]

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.

 

[oldbutnotdead]

Doing the ply as one piece would be very tricky with standard ply sheets at 2400 x 1200. Also any pipes coming up through the floor will be a real pain to do cutouts, as will the whole process of fitting a room-size sheet.
Long as your joists are straight and level, do it in 2 or 3 pieces and join at the joists. If the joists are a bit skinny just sister the ones at the joins with slating batten or 3 x 2 if you want to give yourself plenty of room for cutting errors

 

[johnny2007]

Done it many times.
It takes skills to measure the position of pipes and plan "the drop".
Put a sketch of floor and pipes so we can have a look.
Don't forget waste pipes sticking out of the walls.

 

[ahearsum]

Done it many times.
It takes skills to measure the position of pipes and plan "the drop".
Put a sketch of floor and pipes so we can have a look.
Don't forget waste pipes sticking out of the walls.

Thanks for your reply. I've attached pictures of the planned bathroom (not a quite a plan). I haven't thought through all the practicalities yet but the main question is if I can manage it is it a good idea to have the ply floor as one piece?

 

[domdee]

the 2x1.7m part is the problem as said above. 2.4x1.2 sheets are the norm. I believe you can get 10ftx5ft sheets but are more expensive

 

[ahearsum]

Thanks domdee. I think I complicated this by giving the exact dimensions of my floor. For the sake of argument say my floor is the exact dimensions of one sheet of ply. Is it better to lay it as one piece, if I can, or is there an advantage in laying it in multiple pieces? Four pieces for example? I'm thinking for reasons of thermal expansion (with a small 1-2mm gap between boards) in the same way bridges have expansion gaps.

 

[domdee]

Manageable sized sheets would be my preferred choice. Depends which way your joists run as to how many. Like above, pipes will be easier to route. And the backer board sheets aren’t that big so will be loads of joins in them anyway. Just screw the ply down good and proper and forget about it. Same with the backer board. Use screws that wont rust too

 

[johnny2007]

the 2x1.7m part is the problem as said above. 2.4x1.2 sheets are the norm. I believe you can get 10ftx5ft sheets but are more expensive

This is correct, sorry I missed the measurements.
You will need 2 pieces, so easy piecy.

 

[23vc]

Make sure you add noggins to take all board edges, don’t have any unsupported edge anywhere

 

[ahearsum]

Thanks everyone.