UK Do I need to tank shower over bathtub?

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There was some heated argument in the above thread! I don't have much experience but can see that for the OP, because his wall is gypsum plaster, and with small tiles (so more
grout area), dampness over time could lead to degradation. But i'm still not convinced tanking is required for my own shower bath project.

In my case there will be a standard bath with a shower over. The walls surrounding the bath are brick with a half inch thick cement render. In preparation, the walls had all plaster hacked off back to the bare bricks and were mechanically cleaned prior to rendering with a sand/cement and a plasticiser (sbr maybe?) Then Mapei primer G was applied to the render.

The head/taps end of the bath backs on to a wall adjoining the neighbours property. The neighbour has a shower over his bath the other side of the wall and his is not tanked nor is any special grout or waterproofing used. There is likely ingress into the wall from the neighbours side but it is not noticable as the wall my side is not tiled as yet, so can breathe away any damp.

I will be using 60X30 porcelain tiles with 4mm joints. Calculating the length (7m) and width (4mm) of grout lines over the whole shower area, the combined total area of grout exposed to water will be only about the size of a single 15cm square tile but much more spread out.

I will use keracoll resin cement grout, which absorbs much less water compared with standard 'waterproof' cement grouts. Adhesive is Mapei Keraflex Maxi S1.

So, do I really need to tank around the bath/shower area with a kit such as BAL WP1 or Ardex WPC?

90% of the water will land inside the bath with only the rest bouncing off the person or from the edges of the spray running down the walls. Contrast this with a full height shower, where at least 75% of water will run down the tiles before reaching the tray, or a tiled base with 100% water hitting the tiles with pressure.

But maybe I should still tank as it won't do any harm?

My concerns are:

1. The tanking will not allow moisture from my neighbours side to breathe out through the grout on my side.

2. I might replace the bath tub in a few years or add fixtures for the shower which could compromise/pierce the tanking causing water to leak in and get trapped behind the tanking layer.

3. When the time comes to re-tile once more, it would be easier to remove the
tiles back to the render layer if there is no tanking layer to take off.

4. If a tile gets broken, with no tanking it can be removed and replaced with a spare.

5. It looks messy and I could screw it up.

6. I don't care about the cost or extra work too much so my reasons not to are to keep it simple if I don't need it and 'first do no harm'.

I once lived in a house where there was only a 12inch high splashback around the bath with the walls being plasterboard with emulsion paint around the shower. The paint did start to peel eventually and the wall felt a bit damp but it held up well for years!

So, with cement render brick walls and resin grout and a bath tub catching most of the water, what is the worst that can happen if I do not tank it?

Perhaps it will be OK, until with time, the grout may get old and crack? But even then. the adhesive, cement render and brick will not degrade or cause the tiles to fall off. What about the grout getting mouldy? Can that happen anyway with the adhesive still getting damp even if tanking is used?

I am a beginner and might worry about what is happening behind the tiles, so I would appreciate advice from seasoned professionals.

What kind of problems can I get tank or no tank?

This is going to be hard enough for me to get the tiles on straight without more complications, so I hope you can put my mind at rest.

 

[Tile Marble Granite]

I would waterproof the area, windowsill as well. The bathtub needs to be solid. Create a seal along the tub using Schluter Kerdi Fix, Send us more pictures. Good luck!!