Aquapanel corner

[Mike S]

I wonder whether someone can help me... I've panelled shower cubicle with aquapanel leaving 2-3mm gaps at joins, including the corner. I've read that it is sufficient to join boards with reinforcing tape bedded in with flexible adhesive. But does this make joins sufficiently waterproof? For horizontal joins overlapping them with tiles obviously makes a big difference, but that can't be done at the verticle corner where tile joints will conincide with panel joins? Any thoughts on this anyone?

Many thanks,

Mike

 

[Karis]

I've panelled shower cubicle with aquapanel leaving 2-3mm gaps at joins, including the corner.

Installing with gaps is incorrect & boards should always be close butted, including the corners. All joints should be reinforce taped & bedded with flexy addy & you should do this just before tiling, again with flexible addy. Tile joints should not coincide with board joints if at all possible.

Aquapanel (cement board), tile adhesive & grout (except epoxy) is only waterproof in so much that it won’t disintegrate when wet, it will still absorb moisture so it’s important you get the tile base materials & installation right.

You should always use silicone in corner tile joints, don't use grout.

 

[Mike S]

Thanks for the advice. All makes sense, although in relation to the following:

Installing with gaps is incorrect & boards should always be close butted, including the corners.

.. it seems there is conflicting advice about this as the Wickes guidance sheet on "Working with Aquapanel" says the following: "Aquapanel screws at 200mm centres. Panels should be lightly butted, leaving a 2-3mm gap. The joints are later filled with tile adhesive."..

I'm hoping that is correct as it's not coming down again now. Might it make sense as precaution to put some silicon in the gap I've left between the boards before taping with flexi adhesive?

Thanks again

Mike

 

[Karis]

it seems there is conflicting advice about this

Who does my advice conflict with? Knauf (the manufacturer) recommend to close butt the boards! From many years experience, I can tell its sound practice for any sort of boarding, including plasterboard.

the Wickes guidance sheet on "Working with Aquapanel" says the following: "Aquapanel screws at 200mm centres. Panels should be lightly butted, leaving a 2-3mm gap. The joints are later filled with tile adhesive.".

That’s crap advice & is mainly a throw back to what used to be done with plasterboard 30 odd years ago. Why on earth would you follow a “Wickes” guidance sheet over the product manufacturer installation advice?

A joint filled with tile adhesive is always going to be a weak point. Even when tape reinforce, they are susceptible to cracks but with 3mm of addy in there, you could end up with 2 cracks rather than one which will siphon moisture in there at twice the rate.

Incidentally I usually fix at 150mm but you don’t need to use expensive Aquapanel screws.

I'm hoping that is correct as it's not coming down again now.

Entirely your choice my friend but it’s not ideal.

Might it make sense as precaution to put some silicon in the gap I've left between the boards before taping with flexi adhesive?

Knauf actually make their own & rather expensive joint sealer. I don’t use anything other than flexy adhesive but some seal board joints with silicone but silicone is an enemy as far as any adhesive or finish goes as not much will stick to it. Spread it around too much & you will create all sorts of problems with tile adhesion.

 

[Mike S]

Why on earth would you follow a “Wickes” guidance sheet over the product manufacturer installation advice?.

Because the Aquapanel that I bought did not come with Knauf's installation advice. In fact I had no idea that the product was produced by Knauf, although looking closely I now see in very small print on the instruction label that is attached to each panel that the product is , "manufactured for Wickes by Knauf". On that same sticker there is an illustrated set of instructions that tell the installer amongst other things to "stagger joints and leave 3mm gap". So although my intuition (not expertise, because I'm a novice DIYer) agrees with with your advice about about this, the written instructions told me otherwise, as did other Aquapanel-related posts on this forum emphasising the need for expansion gaps. One post even advised some worried DIYer who had forgotten to leave a gap to cut one in using an angle grinder!

 

[Mike S]

It also occurs to me, and this is pure speculation, that Knauf being a German company might issue instructions for installing in German buildings, which are generally much more solidly built than British ones... lots of steel and concrete, much less timber, and therefore perhaps less likelihood of movement compared to UK buildings.. hence expansion gaps advised for UK but not for German buildings?

That said the cracks that you warn against in flexible tile adhesive will presumably still be a problem with movement, but at least the tiles or panel itself won't be cracking?? Just a thought.

 

[JohnD]

there are still some old buildings left in Germany, and some wooden ones.

 

[Mike S]

there are still some old buildings left in Germany, and some wooden ones.

Yes, you're right of course, although I suspect a German manufacturer of construction materials wouldn't be manufacturing with them in mind.. either way, I've just come across this set of instructions from Knauf itself...

http://www.barbourproductsearch.info/Knauf-Aquapanel-Interior-Brochure-file026742.pdf

seems they have two sets of recommendations, one for "large commercial projects" and the other for "domestic/small commercial projects". For the latter they agree with Wickes: "Ensure all joints between boards are staggered and leave a 3mm gap".

So I guess I'll stick with that and ponder the 'for and against' advice on silicon in the gaps... never realised DIY involved so much time sitting in front of the pc... I was hoping to get away from that!

 

[Karis]

seems they have two sets of recommendations, one for "large commercial projects" and the other for "domestic/small commercial projects". For the latter they agree with Wickes: "Ensure all joints between boards are staggered and leave a 3mm gap".

Just to confuse you further, here’s a 3rd set of Knauf instructions for domestic DIY. http://www.teachmediy.co.uk/NetsiteCMS/pageid/13/Installing Aquapanel/Installing Aquapanel.html

I’ve always close butted & taped the boards (staggered of course), as per the instructions of some years ago when I first started to use it, never had any failure problems. Knauf now seem to be rather confused about it themselves!

 

[Mike S]

Yes, there's a lot of confusion in the world about all sorts of things.. one thing I've learned in life is that there are no perfect answers or solutions to anything, there are nearly always trade-offs somewhere along the line, even within so called 'best-practice', whether in contruction, DIY, or anywhere else for that matter.

That said, in matters DIY, this site is great for avoiding the worst trade-offs, thanks to people like you and other professionals willing to share their experience with novices like myself.

Anyway, thanks again for your response.

Cheers,

Mike

 

[Yukster]

You should always use silicone in corner tile joints, don't use grout.

I plan to use Mapei grey Kerapoxy Epoxy Grout rather than "waterproof" grout. Would I still need to use silicone in corner joints?

 

[Karis]

I plan to use Mapei grey Kerapoxy Epoxy Grout rather than "waterproof" grout.

Is this a conventional domestic shower or wet room & what tiles do you have? Kerapoxy is a high spec product & truly waterproof but with a price premium to match & it’s not so easy to use if you’re inexperienced. There are times when it’s useful but it depends on what you have & is rather OTT for a domestic shower! Your choice of course but a conventional flexy powder adhesive or even a quality tub mix (depending on what tiles you have) & flexy grout will normally be more than adequate in a domestic environment if you get the tile base right.

Would I still need to use silicone in corner joints?

I would always run a bead of matching colour silicone down the corner of two adjacent walls as there is the risk you could get differential movement between the two walls & even epoxy grout will crack if movement is outside its designed flexibility tolerance.