Shower tray - ply on boards or reinforce subfloor?

[ChrisKingston]

Hi,

I'm fitting a new first-floor shower and the edges will not be above joists. Which option is best?

1 replace all the floorboards then just screw 18mm structural ply into the boards, and into joists where can.

2 remove all boards, reinforce joists with new noggins to provide support along edges of tray then screw 18mm structural plywood into joists.

Either way I need to leave room to access the shower waste, which would be bit easier with just screwing ply into boards.

It's an old solid house and the joists and boards are sound, although there might be an extension with walls coming out so want to do what I can to protect this shower from movement. Shower will be enclosed on three sides by new stud walls. Fitting a Mira Flight 900 x 760 x 40 mm tray.

Here's a pic, the little bit of tape shows which side shower trap will be.

Thanks, Chris

 

[DixieDeanLiverpool]

I just put 9 mm ply over the chipboard flooring, having screwed the chipboard down (if replacing it) and then screwing the plywood down at 6 inch intervals each way, but obviously you've got an older house. I then fix the shower using wall board adhesive and push the tray onto it and leave it to go hard for 24 hours. So I would think your best thing would be to screw the boards down, put some plywood over, screw that down and fix the tray using the adhesive. If you're tiling the rest of the floor the plywood should cover that area as well and the tiles fixed on top.