Shower cabinet & bathroom wall tile backing.

[gnnmartin]

My son has a bathroom tiled by the previous owner. The tiles are set directly onto foil backed 9mm plasterboard mounted on a timber frame. There is a shower cubicle in one corner. Water as seeped between the shower base and the wall tiles (we think), and the foil backing on one side of the plasterboard together with the tile cladding on the other has meant there is no way for the water to evaporate away. The water has been drawn by capillary action over a several feet of the plaster board, resulting in a foul black mould under the tiles, and a sodden denatured plasterboard. We are currently breaking out the tiles and cutting away the plasterboard.

The cheapest replacement we've considered is to put back foil backed plasterboard, but back to front, with the foil outwards, and tile onto that. The hope is that if any water does seep through to the plasterboard, it can evaporate away into the cavity in the stud wall. We will ensure the cavity is ventilated into the neighbouring hall. Are we being too cheapskate? Am I right in assuming that the paper finish to the (nominal) front face of a foil backed plasterboard is vapour permeable?

The next more expensive solution is to replace the plaster board with 9mm Hardibacker, and tile onto that. Can one screw 9mm Hardibacker directly to the studs without any backing support? I guess it is as strong as plasterboard, so I guess the answer is yes, but I haven't found anything actually saying that Hardibacker can be used in this way.

In either case we thought we might use the 'flashing' extras sold as part of the the Homelux seal system broken link removed to seal between the tiles/backer and the shower base, and in the corner of the wall. I'm slightly concerned whether mixing systems like this is asking for problems.

Any comments will be much appreciated.
Nigel Martin
PS. I did hesitate about putting it in the 'hi' forum: sorry if I got it wrong!

 

[DHTiling]

hello nigel and welcome to the forums....this forum was ok for your thread.....
as for the leak...you need to stop the leak full stop..you need to replace all effected parts of the wall and replace with a backerboard.....make sure all joints are watertight.....before re-tiling.......Me personally i would tank the new area just to make sure...you don't want this happening again..........

The leak could be the joint between the tray and wall tile or even just water ingression through the joints...so tanking will stop the ingression damaging the substrate again and you need to make you have a good seal at the base as well....

good luck.........

 

[Turkish]

Hi mate and welcome to the forums, loads of great advice here!

Turkish

 

[robbo]

Welcome to the forums bud

 

[sWe]

Hi Nigel. It's always better, and cheaper (in the long run), to do a proper job once, than skimping, and having to redo.

Plasterboard is usually covered by some sort of cellulose based material, and if it's regularly exposed to humidity, there will be black mold, as the black mold feeds off damp cellulose.

Plaster isn't normally water resistant either. By the way, don't confuse water resistant with water proof. Something being "water resistant" means it won't deteriorate under the influence of water. It will still let moisture pass through it, given enough time.

Ventilating through a wall isn't a good idea. It is much better to waterproof thoroughly and then let damp air escape through proper ventilation channels.

I'd use backerboards or aquapanel, screw them onto the joists (which should have 45cm spacing, at the most) with 20cm spacing of the srews, and then I'd waterproof everything.
Take extra care to waterproof all the corners and around the drain, as that's where the exposure to water is going to be the greatest. I'd use a WPC system with joint/corner tapes, and fabric gaskets, to waterproof backerboard.
Water and steam proof foil/membranes are even better.

The initial cost of doing a bathroom renovation properly is higher than if you skimp, but you won't have to redo everything in a few years, or risk allergies due to black mold spores in the air.

 

[Kobbie]

Hello and welcome

 

[gnnmartin]

I don't seem to have got the hang of this forum yet. But anyhow, thanks to Dave and sWe for your advice. You've convinced me to use a backer board at least.

I agree fixing the leak is essential. As for ventilating the wall space, that is not an attempt to ventilate the bathroom, is that what you thought I meant? It is just to allow any moisture that does get through to the wall space (even though it shouldn't) to escape rather than sit there and rot the studs.

Anyhow, thanks again for the advice.
Nigel Martin

 

[sWe]

As for ventilating the wall space, that is not an attempt to ventilate the bathroom, is that what you thought I meant? It is just to allow any moisture that does get through to the wall space (even though it shouldn't) to escape rather than sit there and rot the studs.

I understand what you meant, but it's still not a good solution 🙂
It's better if no moisture can get in behind the walls in the first place. Moisture in surpricingly small amounts can propagate mold (wood is mostly cellulose = black mold = allergenic, and really expensive to get rid off), deterioration of the framework, and structural movement, which can have a number of adverse effect.

Someone on these forums has a signature which reads "buy cheap, buy twice", and that's very true in bathrooms and showers.

 

[gnnmartin]

Thanks.

 

[monty]

Hello and welcome to the forums...... 😉