Large format tiles - Remove concrete skim?

[paulo-m]

Hi Everyone,

I'm looking into retyling my bathroom. It has 2 concrete walls - skimmed and painted - and 2 plasterboard walls partially tiled, partially skimmed and painted. The tiles I'll be using are 10mm thick porcelain in a variety of sizes, from 15x90cm up to 45x90cm.

I've read a lot about the max weight that plasterboard can support, both skimmed and unskimmed and also concrete walls. It's clear that I need to replace the drywalls with cement boards, which I'm doing as we speak.
However for the concrete wall I can't find much information regarding the weight, mainly how much weight does a skimmed concrete wall stand? I imagine I should remove the paint from the concrete wall, but should I also remove the skimming in order to expose the raw concrete?

Thanks in advance for your help!
Paulo

 

[Tile Shop]

If by concrete you mean Render (sand/cement), on it own un-skimmed, it can hold upto 50Kgs safely.

As soon as anything is skimmed, whether it be render, plasterboard or cement boards the limit is immediately reduced to 20Kg's because plaster is a bit of a pansy

 

[paulo-m]

If by concrete you mean Render (sand/cement), on it own un-skimmed, it can hold upto 50Kgs safely.

As soon as anything is skimmed, whether it be render, plasterboard or cement boards the limit is immediately reduced to 20Kg's because plaster is a bit of a pansy

Thanks for the explanation! makes total sense.
The skimming there is at the moment doesn't seem to be 100% plaster since it's greyish. I imagine it would be some kind of plaster mixed with cement. In any case the take away is to remove it and expose the render.

Cheers,

 

[Blunt Tool]

Thanks for the explanation! makes total sense.
The skimming there is at the moment doesn't seem to be 100% plaster since it's greyish. I imagine it would be some kind of plaster mixed with cement. In any case the take away is to remove it and expose the render.

Cheers,

You could glue and mechanical fix Wedi, Marmox etc insulation boards and will increase weight bearing substantially.