Having come across the forum recently my head is now swimming with info that needs a bit of clarifying...

We're preparing the renovation of a bathroom and shower room, walls presently are plasterboard and rotten, floors are chipboard and generally sound but flexy. Two walls in each room are external blockwork walls. Showers and baths will be fitted to the plasterboard walls only. The plan is also to have electric undertile heating.

First question: obviously the floors will need prep for the floor tiles and insulating for the UTH. Are we best to remove the chipboard and install something else, if so what? Do we overboard the chipboard with ply or tile backer board instead? Hoping not to raise the floor level much if at all, which to me suggests replacing the chipboard with something suitable. Any guidance welcome.

Secondly, prepping for wall tiles and waterproofing the shower area. As we are ripping out the mouldy soggy plasterboard we can replace it with anything we want, the question is what. The two options appear to be tile backing board or plasterboard with waterproof tanking, be it paint-on like Bal WP1 or membrane as Wetdecs sells. I'm inclined towards plasterboard with treatment but that is only because of the cost difference. If tile backer board is a better solution then please point that out to me.

That's it for now, thanks for any help offered.

Hi and welcome

yes rip the floor up and replace with 18mm wbp ply screwed at 300 centres, you will need to add noggins to brace the joists and to carry the ends of the boards

prime the underside of the the ply before laying, primer g or bal apd

you can overlay the boards with backerboards fixed with addy to give the ideal tiling surface

before giving advice on the walls what tiles do you plan to use

ive just reread your post, no need for the backer boards if your having ufh

Hi Mike, thanks for the advice.

At the moment the wall tile choice is between mosaics and the brick-sized bevel-edged metro tiles, so not especially heavy. We've done the stone walls thing before and I don't want to do that again...

in that case plasterboard and tank in the wet areas

Thanks Mike, a couple more quick questions to lead on.

What do you do with the joins between the floor ply? Rout on a tongue and groove? Tape? Some other jointing method?

Secondly, what tanking method do you prefer? Paint on or membrane? Which product?

Again, thanks for your help.

Hi

no need to joint boards , just butt them as you will be laying ufh on them anyway