Tanking and using stone tiles - TilersForums.co.uk | Tile Forums

itaylort · 09-09-2008

Hi all,
quick intro
My name is Ian and i have just finished 22 years in the army as a mechanic. Im currently taking some time off renovating a house.
Im in the bathroomat the moment and have come to a halt while i look into the shower area.

The wife wants travertine tiles on the floor and on the shower walls. To my investigating:-
One wall of the shower is overbaorded 9.5mm plasterboard mist coated with wickes trade new plaster paint. the other wall is only at the stud wall stage, it will probably be either plasterboard or WBP exterior ply.
Am i correct in tnikning that plasterboard is ok to use in a correctly tanked shower?
a plasterboard wall can take with bal wp1 30ish kg/m2 and a plastered wall 20kg/m2.
i believe travertine comes in at 30 ish kg/m2.

Im really looking for some correction to my thinking and direction to the walls so they will hold trav tiles and be waterproof.

Many Thanks for any help

Ian

**grumpygrouter** · 09-09-2008

Hi Ian, welcome to the forums. You are about right with your weights, bare plasterboard will take 32kg/m2 with a plaster skim that drops to 20kg and that is the same as a normal plastered wall.

If you want to use travertine, then bare plasterboard at a minimum, is required. If possible, avoid using ply on walls in bathrooms for tiling onto. Plasterboard is OK in the shower area as long as you tank it porperly. I have recently started to use membrane for this and it is quite easy to use. Check out our sponsors Wetdecs for this, tell them Tilersforums sent you.......

itaylort · 09-09-2008

Hi Grumpgrouter, Thanks for the reply.

Would it be ok to then overboard my existing skim with 9.5 plasterboard?
then i will have the 2 walls in plasterboard. The stud wall will be 12.5.I can screw them both at 300mm centres also.
I will checl out the wetdecs site now. Do you rate this over Bal WP1?

Ian

**grumpygrouter** · 09-09-2008

You will need to mechanically fix the overboarding to benefit form the additional capacity of the plasterboard, and also really it should be 12.5mm for the stated weight limit.

To be honest, and this is the safest way bearing in mind the weight of natural stone, you would be better removing the 9.mm plasterboard and fitting cement based backerboard instead. There are various types available such as Hardiebacker 500 or Aquapanel (from Wickes for instance). These are more expensive to buy but have much greater weight capacity and you will only need to seal the joins between the boards to become waterproof as they are unaffected by water, unlike plasterboard which could collapse if it got wet. Again these should be mechanically fixed.

I have never used the BAL product you mention though I have used the Durabase C1 membrane which is very good and easy to apply using cement based adhesive.

itaylort · 09-09-2008

Grumpygrouter,
I have seen the aquapanel in wickes, but not the hardiebacker. Where can you get that from.
I believe the aquapanel is not waterprrof only water resistant ie it will not fall to bits when wet. So this means it will still require to be tanked in some way. Is this correct?

Ian

**grumpygrouter** · 09-09-2008

Quote:

Originally Posted by itaylort

Grumpygrouter,
I have seen the aquapanel in wickes, but not the hardiebacker. Where can you get that from.
I believe the aquapanel is not waterprrof only water resistant ie it will not fall to bits when wet. So this means it will still require to be tanked in some way. Is this correct?

Ian

You can get the hardiebacker from (i believe) CTD and definately Topps. The idea of tanking is to stop moisture/water from coming into contact with perishable substrates like plaster/plasterboard. As aquapanel, like Hardie does not break down if it comes into contact with water, there is no real reason to tank it. I know some people do, but I don't.

If on the other hand you are looking to completely isolate the area so that any leakage does not get through to an other area, downstairs for instance, then you are talking a whole differerent ball game as you would need to seal the floor as well.

In the normal scheme of things, tanking will protect problematice substrates from water penetration via cracked/missing grout or from the absorption that all grout, apart from epoxy has. If this is the reason you wish to "waterproof" the area then cement based boards will be fine. Just remember to seal the joins between the boards.

itaylort · 09-09-2008

grumpygrouter,

I have a shower enclosure, with a tray, so i was looking to seal the walls down to the tray really to stop anything running downstairs or being absorbed into the wall area and popping the tiles.

I was under the impression that waterproof grout is not really watertight and that most tiles are to some extent porous. That was the reason for the tanking really

Ian

**grumpygrouter** · 09-09-2008

You are correct about the grout, and adhesive incidently. However, unless you have a huge amount of water hitting the tiles, any water absorbed into the grout will evaporate back out again as long as there is plent of ventilation. The reason tiles will pop off is if the adhesive fails or the substrate collapses. If you have decent adhesive (for tubbed stuff, white star for instance) or a powder based adhesive the water will have no effect as it doesn't break down so your tiles will stay safe. This is the reason tanking is recommended - to stop moisture getting to the substrate. if you use cement based backer board as opposed to tanking, it will not breakdown with water, neither will your adhesive so your tiles will stay put.

Alice · 09-09-2008

I'm no expert - far from it. In fact we are in the same kind of situation as you - about to apply travertine tiles and have a shower tray (not wetroom). So the advice we've been given seems to be to use backing board (like those produced by wedi) then seal the joins and use a tanking kit. Seal the tiles prior to putting them on, then again prior to grouting, then again after grouting. Use a flexible water-resistant adhesive - for walls that is (we have wooden floors and aren't tiling there). Hope it helps. Would be interested to hear what you find out, too.
Alice

itaylort · 09-09-2008

Thanks for the support so far, could i just clarify-

If i was to install aquapanel to either side of my shower and seal the joints with aquapanel tape and jointing compound this will hold the full weight of stone tiles using a high bond adhesive like white star. Then using a flexible waterproof grout.
i should be able to direct fix the aquapanel over my existing lovely overboarded skimmed and painted wall. Fixing at 250mm centres, as surley this is the same as fixing it to battens or studwork.

When the water hits the tiles only a minimal amount of water will be absorbed into the grout in a domestic use shower. This will then evapourate between showers.
So this negates the need for a tanking to be used.

If any water does pass through the tiles it will be absorbed into the aquapanel and then evapourate without destroying the board.

Is the aquapanel sealed at the shower tray and then at the base of the lower tiles to prevent water penetration there?

Or for piece of mind should the panels be tanked anyway?

Thanks again for humouring me on this

Ian

**grumpygrouter** · 09-09-2008

Quote:

Originally Posted by itaylort

Thanks for the support so far, could i just clarify-

If i was to install aquapanel to either side of my shower and seal the joints with aquapanel tape and jointing compound this will hold the full weight of stone tiles using a high bond adhesive like white star. Then using a flexible waterproof grout.
i should be able to direct fix the aquapanel over my existing lovely overboarded skimmed and painted wall. Fixing at 250mm centres, as surley this is the same as fixing it to battens or studwork.

When the water hits the tiles only a minimal amount of water will be absorbed into the grout in a domestic use shower. This will then evapourate between showers.
So this negates the need for a tanking to be used.

If any water does pass through the tiles it will be absorbed into the aquapanel and then evapourate without destroying the board.

Is the aquapanel sealed at the shower tray and then at the base of the lower tiles to prevent water penetration there?

Or for piece of mind should the panels be tanked anyway?

Thanks again for humouring me on this

Ian

Hi Ian, my apologies for a bit of confusion, I would not use white star in this situation, I only mentioned it as part of my example, you will need a cement based adhesive with your tiles as they are natural stone. As for the rest of your response, yes it is fine, except that if you are going to put the cement board over the top of your plasterboard ensure you screw it through into the studs. Personally I would remove the plasterboard first.
Again don't assume grout is waterproof unless you intend to use epoxy grout. They are resistant ot breaking down when in contact with water but they will allow water to permeate through, but yes, it will dry off again.

My recommendation for an adhesive would be something like BAL Rapidset flexy in white. Because rapid set sets a much quicker, you will have less problem with moisture pentrating your stone tiles than if you used a standard set adhesive. Just make sure you mix up in small batches at a time.

itaylort · 21-09-2008

Hi,
scrapped the stone and gone for ceramic now.

I have been looking at the Dunlop shower kit as an alternative to Bal kit, but in the dunlop instructionnal video it states only to apply the product to 1m high. While i appreciate most of the water will be around the bottom end surely it would be far more beneficial to be higher up than that.

I would appreciate your thoughts

Ian