Waterproofing a Shower Area



Hi All,

I have just joined the community so I hope I have opened this thread in the right forum area.

I have done a lot of research on this topic but I still have questions that I can't seem to get an answer to.

My plan was to fit moisture resistant plaster board in the shower cubicle, apply tiling primer,followed by tanking paint. I would then tile onto the tanked areas and grout the tiles.

I am planning to use a shower tray with tiling upstands with the tiles lipping over the upstands and sealed to the tray intself with silicone sealant.

I have however just realised that there seems to be a problem with this.

The reason I am proposing to use tanking is because tile grout and tile adhesive do not form a 100% water barrier. The tanking therefore would give this 100% water barrier instead.

My problem is as follows: If the water does penetrate through the grout onto the tanking interface it would then have no choice but to seep down the tanked wall behind the tiles. When this moisure gets to the bottom where the shower tray is located it would seep into the shower tray (assuming that I have rebated the upstands into the wall slightly). The problem is however that the water cannot drain away from this point because the shower tray is silicone sealed to the tiles. The water would then effectively be trapped between the tanked wall and the silicone sealant.

Have I missed something because I can't see a solution to this.

Any and all help would be much appreciated.

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Rather then use MR plasterboard in the wet area, you’d do better to fit waterproof tile backer board & tile straight onto that. By the time you factor in the additional cost & work of tanking the difference is going to be negligible & backer board is a far better solution. What are the boards being fixed to, studwork or block/brickwork?

Your train of thought isn’t wrong but if you use quality materials of the correct type, you’re worrying unnecessarily. I prefer trays without an up stand & set this so the tiles overlap the top of the tray; problem is that unless an up stand tray fits exactly it will throw the first row of tiles out but your choice. You can silicone the tray to the wall but I don’t & you need to be careful when using silicone before tiling as not much sticks to it including tile adhesive. I fit the tray & tile leaving a 2mm gap to the top of the tray. Using a new nozzle I force silicone into the gap to fill the void completely; I then clean off the excess, cut the nozzle to the required bead size & immediately apply a second bead between the top of the tray & bottom of the tile & smooth off as normal. You should also use silicone the vertical corners where the walls meet rather than using grout which will crack if there is any differential movement between the two walls. What size/weight/type are you tiles?
Yes the boards will be fitted to studwork rather than block/brickwork

Are the tile backer boards the same as aquapanel?

I had considered Aquapanel but there seems to be a lot of debate on whether using it removes the need for tanking so I wasn't 100% sure that it would be preferable.

I guess I'm still a bit unclear on the tanking issue because in a way it seems that with tanking you automatically create a cavity between the silicone of the shower tray and the wall where water could be trapped should the grout fail. The only way for this to definately not occur is if the tile grout and adhesive create a 100% water barrier. But there seems to be a general consensus that they don't. It seems therefore that there is no 100% watertight solution unless you silicone the tanked board to the shower tray, then fit the tiles on top and do not silicone the tiles to the tray (a tray with upstands that is) so that there is a direct water drainage path down the tanked wall into the tray should the tile grout & adhesive allow some seepage. But there are two issue with that: nothing sticks to silicone as you have stated and the only way to repair the silicone seal should there be a need to do so would entail removing tiles.

I haven't yet considered what weight of tiles but it seems I will be limited to about 32kg/Sq Metre including the adhesive and grout. I'll probably use largish format tiles but ultimately my wife will choose these in time :)
have you already bought the tiles? as there is an easier option.....

You can fit shower wall panelling or upvc panels directly to the walls, and they provide a full waterproof finish.
I did it in my house, and it definately saves all the messing about. I used a company in Staffordshire called Just Plastics, they have a decent website, with extra info on fitting etc on there.

I have dealt with them twice and they have been really helpful both times.
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That is a really good suggestion as I haven't bought the tiles yet.

It seems to me that doing it that way would give a 100% waterproof solution that would be far easier to install, maintain and clean.

I've had a look on their site and it may be the way to go.

Thanks for the suggestion :)

Personally I don’t think panels look anywhere near as classy & professional as a decent tile job, large format tiles look great & will significantly reduce the already low risk when it’s done correctly. Failure rate with the correct preparation & quality tiling products is very low; my personal remedial/failure rate is zero since I started doing this in 2005. Can you say if panels are the way you’re going as I don’t really want to be going into a lot more detail if I’m wasting my time. ;)
I'm having a look at the panels online to see if there is a wide selection in terms of colour. You could be right that the finish in tiles might look better therefore I'd also need to get samples to assess this so the honest answer is that I'm not fully decided yet.

I guess that I'm still not ruling using tiles out completely but I need to understand the issue that I originally raised as I feel I must be missing something on the part about water being potentially trapped between the tanked wall and the tile/shower tray silicone seal. If the grout is 100% waterproof then there is no issue. If it is not then having a tanked wall or using a waterpfoof backboard still raises that issue potentially.
I don’t know if you’ve had a previous bad experience; you seem to be doing the research & your basic understanding the problems are sound but, IMO, your being rather paranoid about how far you need to go for what you are doing. If your prep is good & you use quality materials, correct for the application – be it shower/bath/wet room/ blast shower, you won’t have any problems.

There are several pro tillers & at least one supplier on this forum & given the right information will advise what you need to do & what materials to use. Have confidence in yourself, post what you have, what you want to achieve & you will get good advice.
Hi glyde, Richard C is obviously not a fan of the panelling.
I think it is personal choice.
There is lots of advice if you decide to go with tiles.

And I also think there are some cheap wall panels and some very nice (and very expensive) wall panels.
Panelling is always goign to be quicker for you to install, and it seems to me that you are very worried about water, so I would still lean to the panelling....

Whatever you choose, keep us posted as to how you get on :)
Glyde, if your tiling and i would personally then follow rich c's advice to the letter.

Read his past posts the chap knows his stuff :D

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