waterproofing aquapanel

[wellerman]

got the walls lined with aquapanel and almost ready to tile aprt from adhesive/tape on the joints which I was going to do just before tiling commences.

I was also going to use BAL WP1 waterproofing kit on the cement board and in particular the joints to ensure there is no trouble in the future.
On reading the spec sheet it advises that you should:
"Apply a skim coat of a BAL cement-based adhesive modified with BAL-ADMIX AD1, prior to the application of the BAL-WP1 TANKING SYSTEM. Allow adhesive to set."

This would then mean I'm tiling to a wall that has dried adhesive on it.

Is that OK to do, or can I just paint on the WP1 to the aquapanel?

 

[Richard C]

Are you referring to Knauf Aquapanel? If so, why are you tanking? It’s already waterproof & dimensionally stable even when totally immersed. Just seal the joints, tape & tile straight over it is all I do; tanking Aquapanel is overkill in a domestic shower environment & would only really be wise in the case of a wet room floor construction.

 

[wellerman]

I just wanted to be sure!

That's fine then - at least I've saved a few quid!!

Cheers Richard

 

[Richard C]

Rather a strange way of "being sure"; why not just ask what you should do

 

[wellerman]

Belt and braces....

 

[piper64]

Are you referring to Knauf Aquapanel? If so, why are you tanking? It’s already waterproof & dimensionally stable even when totally immersed. Just seal the joints, tape & tile straight over it is all I do; tanking Aquapanel is overkill in a domestic shower environment & would only really be wise in the case of a wet room floor construction.

I know its an old thread but you mention taping the joints. This is exactly what I'm trying to do with the DeltaBoards I've used to board the shower area, ( despite being told that I only needed to silicone them) but I'm not able to find a stand-alone waterproof jointing tape, just some expensive tanking 'kits' which contain stuff I don't need.

I've found Aquafix to order on line, but would it 'stick' to Deltaboards? It seems more designed for flat surface but they have a bumpy mesh pattern on them, so I was thinking of using scrim and a waterproof paste of some sort?

Any pointers?

 

[Richard C]

I’m a little out of touch these days & have not actively posted the Forum for some years. I’m not familiar with Delta boards as I only ever used Aquapanel cement board but if they are of similar construction, it shouldn’t make any difference. The joint tape I used was ordinary fibre mesh plasterboard tape; it’s slightly tacky so is self adhesive but brush off any dust from the board surface before hand & if you want “belt & braces” approach, triple tape the joints, over lapping the central board joint. Lightly skim over the joints with tile adhesive to securely hold the tape in place & once this has gone off, apply your layer of tile adhesive & tile away. Only use a top quality cement based tile adhesive if you want it to last, especially if using large format tiles. I'm sure current contributors are just as knowledgeable but I have hundreds of previous posts in tiling & plastering which should answer most if not all of your questions.

 

[piper64]

Hi Richard. Deltaboards are foam core cement faced boards, so lighter and easier to work with than Aquapanel. They also offer a waterproof barrier due to the foam core.
The original idea was to do as you've said, I even bought alkali resistant scrim, but it all changed once 'tanking' was mentioned. Even the board manufacturers said they should be 'tanked' at the joins. Then I got all paranoid about it, but maybe I'll revert to my original idea, same as you've suggested. I imagine that the most likely area for water ingress is going to be around the tray, so I'll concentrate my waterproofing efforts there.

 

[Richard C]

As my original reply, tanking Aquapanel is a bit OTT in a domestic shower; many say the scrim tape should be specialist, alkali resistant but Gypsum plaster & cement is alkaline so standard fibre glass tape should be Ok as far as I’ve ever been aware. It’s all I ever used as I always had loads around for plastering jobs & I never had any failures.

You can bed the board joints with silicone on the lower two thirds of the shower walls but don’t get silicone on the tile face as the adhesive won’t stick to it. Re shower tray sealing, I always slightly overlapped the tray with the tile boards where ever possible & run a silicone bead seal under the board, tile & then run another silicone bead between the tray & underside of the tiles, let this go off before applying the finish silicone bead around the edge of the tray. Also run a silicone bead down the corners of adjacent shower walls instead of using/relying purely on grout, this can crack (even after scrimming) due to differential movement between the walls & siphon in water leading to tile failure.

Are you screw fixing the Delta boards? I would not rely on adhesive alone if you are using large format tiles over 300mm square. These are quiet heavy & you will have an additional potential failure point between the walls & the boards if you rely on just adhesive.

I've moved on from all this now but developed/used my methods for some years after a couple of problems initialy but never had any failures or complaints after that.

 

[piper64]

Hi Richard

I agree that tanking is OTT of these boards, but my concern is where the boards meet and the vertical corners, which must be a weak point regarding waterproofing proprties of these boards, which is purely down to the foam core.

For extra support I am using mechanical fixings on the boards, which raises another question. Surely making holes in the cement board has compromised the 'waterproofness' of the foam inner? Moisture wiill happily travel along the fixing and directly into the wall that it's screwed into, won't it? Checked the tech sheets and no mention of this being a problem, but at one point deep down in the blurb, it mentions sealing the joins and holes with tape.

Not easy is it?

 

[Richard C]

Tiling is not really rocket science, just experience of understanding potential points of weakness, what works & what doesn’t. You’re clearly thinking about it, nothing lasts for ever but get it right & use only high quality products, correct for their application & it should last at least 10 years & possibly up to 20 years. I would never advise using cheap, DIY shed products although I seem to remember some do stock Mapei.

Although quality grout is water proof, it’s cracks in the grout or between the tiles & the shower tray that allow water to siphon back into the substrate which will then, eventually fail. You are right to see the vertical corners of the shower as a potential weak point & why I advise not to rely on tile grout here. You should still tape the corners of the boards but only grout the tiles up to the corner, not the corner itself; force silicone into the gap, let this go off & finish off the shower corners with a silicone bead. If you’re going for a colour grout, matching could be an issue but I only ever advise using white which I think always looks best.

Re the screw heads; only use zink plated screws, recess the heads slightly, fill the heads with tile cement, apply a square of tape over the head & skim over the surface of the tape with more adhesive as before which will hold it in place when you tile.

 

[piper64]

I've ordered some MapeiWPS and 25m of Mira Safe Fibre carrier tape. Should do the verticals and board joins with enough left to patch over the fixings.

I already intended to do the corners with silicone, it's really the only way to get anythng at all in there. Going with grey, to compliment the tiles and be less conspicuous if the grout gets dirty!

 

[Richard C]

I only ever used BAL products &, although rather expensive, they are the best available IMO. As I said previously, gypsum plaster & cement render are alkaline so standard plasterboard tape must be alkali resistant anyway, why use far more expensive “tiling application tapes” when the products involved are mostly cement based! Using standard, inexpensive fibre glass board tape has never caused me any problems!

White grout still looks far better on any wall tile installation in my opinion as long as you look after it; not so with floor tiles but that’s another story! Quality, bacteria resistant grout products are impervious as long as the surface remains undamaged so, under normal household use, it will never really get “dirty” as such. What happens is hard water lime scale will quite quickly build up on the grout surface & it’s this lime scale covering that starts to discolour & will even allow black mould to fester. A water softener makes one hell of a difference as it prevents build up of lime scale but a monthly spray clean with a quality (industrial if you can get it) lime scale remover will keep it all looking good.

 

[piper64]

Limescale is a problem here, even though I have Salamanders on both cold feeds. The tile adhesive already being used is grey, due to the plan to use grey grout. White grout is nice, but I didn't want a 'stand out' white grid on the tiled wall, as it's not so big a room. If I'm careful with the tile adhesive, I can always change my mind and use white grout.

 

[freddiemercurystwin]

Good to see you again Richard C!