Bath Pipes Covered By Single Plasterboard-Crumbling.must I Replace Plasterboard?

[Clare2424]

Hi, I removed 2 layers of small tiles from around my bath. Plasterboard now is cracking (can be seen from behind the plasterboard i.e. all the way through crumbling about 3 inches). It's hollow behind, a lot of pipes. My tiles are 50cm by 25cm ceramic. Weigh 16kg per sq metre. So i'll be putting 3 or 3.5 levels of tiles on this wall depending if i go all the way to the top. I'll be stripping the whole bathroom in 5 years and changing layout so i'm hoping not to have to put new batons etc. in now. Would it be OK to fill the crumbling parts and nail a new layer of plasterboard on the top (into the same batons underneath if this is possible with long nails?) or would this likely cause further crumbling of the existing board/ the weakened base be problematic/ not support the one on top and tiles properly? If the existing plasterboard needs removing is it possible to replace and nail in without having to move the bath (as it extends a few inches below the top of the bath).

[The Builder]

I guess this was tiled some time ago, and most likely, ordinary plasterboard was used. This will degrade and crumble since moisture will always permeate into the board.

"Moisture resistant plasterboard is designed for this use........ or something like "Hardie Backerboard".

Since you're going to be stripping the whole lot out eventually, I think your best bet is to just replace the crumbled bit with plywood. Drill the ply and screw it to the battens. Nailing might well loosen everything up with the banging.

Once the bottom tiles and the crumbled board is removed, you should be able to slide the ply down behind the bath Ok.