Installing a Stone Resin Shower Tray on Wooden Floor Boards

[It's me]

We are planning to fit a stone resin shower tray into an upstairs bathroom that has wooden floor boards. It needs to be as low as possible and not up on adjustable legs.

I plan to ensure that the existing boards are in sound condition and then lay a thick sheet of WBP plyboard (18mm or so) on top of this for strength. I plan to take time to get the board level and true by using either mortar or a floor tile adhesive between the floor boards and the ply. Once this is done, I plan to sit the tray on top of the ply, butted up to the wall which will be tiled afterwards. I shall make sure that the waste is all in place first and that I have cut access holes and so forth.

Does this sound like a sensible plan or should I be doing it differently?

James.

 

[Dereekoo]

When I put mine down many years ago, the ply was just screwed down to the floorboards and the resin tray layed on a bed of mortar

 

[oldbutnotdead]

Those resin trays all need even support. The lump of ply over the floorboards is good (stops differential movement) but you need the mortar between ply and tray- the idea is the mortar squidges up into all the little undulations and uniformly supports the thing.
If yours is the type that offers a leg kit (on the underside there'll be some clear load points) I suppose you could just use big mortar dots at those points but if you're going that far you might as well follow the Mfr instructions on the thing.

 

[It's me]

That makes sense. Thank you.

 

[Madrab]

Lift the floor boards and check the joists - run supports(noggins) in between the joists (every 300mm) to provide lateral support to the floor boards to minimise flex in the boards. Double screw the boards down at every joists/support.

Ensure there is a rectangle/square of joists/noggins that's tracing the outline of the tray. Use packers to level out the ply, don't use an adhesive as the floorboards will move/expand/contract and can break up the adhesive over time. Screw the overlay down every 100mm.

Some use mortar some use adhesives to bed the tray. Personally I use a good quality silicone adhesive (not sealant) to bed the tray into as it hardens to a stiff rubber that allows it to absorb a little flex when the floor moves so minimises the pull on the wall/floor seals (silicone sealant).

 

[It's me]

Thank you.

 

[It's me]

Resurrecting this thread. Rather than using plywood underneath the shower tray, is there any good reason not to use cement board such as Hardie or no more ply?

 

[It's me]

I should have added that we are planning to fit a Tissino Giorgio tray.

 

[Madrab]

Depends on the thickness I guess, 12mm would be the min I suggest. Just remember there is no sure way to really secure the cement board to the floorboards unless you use bespoke screws and countersink them.

 

[It's me]

Thank you.