Plasterboard on shower tray

[mike42]

The new shower tray is going to be a really tight fit so was thinking of bedding in the tray first then adding green plasterboard resting on the top of it (then tanking then tiling).

Would that be ok or is there a good reason I haven't thought of as to why the plasterboard needs to go behind the tray?

 

[Newboy]

Really bad idea. The exposed edge of the plasterboard will exposed to water if (when) the seal breaks down and/or there is slightest movement of the tray.

Don't use plasterboard in a shower area - use a suitable tilebacker (cement board)

 

[mike42]

Many thanks for that although I thought tanked plasterbaord was almost as good.

Anyway, if I do the same thing but with the cement board resting on the top (no plasterboard) would that be ok? I just can't see how else to get the tray in 8-(

 

[Newboy]

What're the tray sides up against?

 

[mike42]

Wooden studs from the wall.

 

[Newboy]

Personally I'd look for a shower tray that fits into the space once boarded.

 

[polesapart]

No problem IMO with waterproof board overhanging the tray but check that the shower screen dimensions will be within tolerance after tiling.

 

[dilalio]

Hardiebacker or wedi board can come down onto the top of the tray... Just be sure to silicone the tray to those boards and then silicone again when tiled. BUT... as @polesapart said... Check your min/max screen tolerances.

 

[mike42]

Bloody marvelous !

That's already solved my problem but would be even easier if I could use green pb and then tank it? Is the issue with that a general case of it being inferior to cement board or wedi/marmox/etc? Or is it somehow more specific to this case where the board comes from the top? I guess a flexi sealing strip wouldn't help either?

I've no objection as such to using either the more expensive boards or the very heavy cement ones but if I can do it reasonably well with cheaper/lighter I'd obviously prefer that (but not if it is 100% a terrible idea).

 

[Madrab]

One's waterproof the other isn't.

Green backed PB isn't waterproof, it's moisture resistant. You wouldn't be able to ensure that it was totally waterproof, even with tanking unless the tanking membrane was wrapped from behind and then around the bottom/side edges and then up the front of the board to ensure that water couldn't get to the core by any manner. Very hard to make PB 100% waterproof unless it's in first & then tanked before the tray goes in.