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Heavy Tiles and Liquid Membrane - Can They Work?

  • 08-01-2023 11:46am
    Registered Users Posts: 34

    Hi Everyone,

    Happy New Year! Hope someone can shed some light on this for me. I'm re-tiling our wet room and have covered the walls in XPS foam/cement backer boards. These were recommended because the tiles we are using are large format, heavy-ish, and need to be able to stick to the wall properly.

    I'm planning on using a paint on membrane in the shower area to help with waterproofing, however, what concerns me, is that will the tile be able to stick to the backer board (properly) if it has a membrane painted over it? I understand this is fine for wall tiles, but what about 60cm heavy-ish floor tiles being used on the wall? Will the membrane lessen how heavy the tile can be?

    Thanks, Ryan


  • Registered Users Posts: 7,785 ✭✭✭Rows Grower

    The paint on membrane is specifically designed to accept tile adhesive and should come with a lifetime warranty once instructions are followed. The backer board will be more likely to fall off if not fixed properly, that is assuming the tiling work itself is done properly.

    "Very soon we are going to Mars. You wouldn't have been going to Mars if my opponent won, that I can tell you. You wouldn't even be thinking about it."

    Donald Trump, March 13th 2018.

  • Registered Users Posts: 6,570 ✭✭✭10-10-20

    I'm not a tiler, but I had a look at the spec sheet for the Mapei tanking product to see if a shear value or adherence pressure was stated but it's not.

    I believe that how it works is that as the tanking compound is applied as a thin coat (0.8mm wet, 0.5mm dry) and given that it has a very good adherence to the substrate surface (providing that the spec sheet is followed), it carries over the effective strength of the substrate. Clearly dust and moisture will affect that adherence, so the prep is key.

    That's my understanding of it - open to correction.

    Post edited by 10-10-20 on

  • Registered Users Posts: 73 ✭✭Le shovelle

    The adhesive will stick to the membrane no problem.

    On a side note: when using large format tiles, it's recommended to butter a thin layer of adhesive onto the back of the tile as well as coating the wall.

  • Registered Users Posts: 34 rymass

    Hi all, thanks for the valuable info. Backer boards should hopefully not fall down :) (tiles may be a different story as I'm not too experienced). But I've used adhesive and mechanical fixings to keep the boards strongly in place. Will be reading the spec sheets of several membrane products before I use them

  • Registered Users Posts: 38,979 ✭✭✭✭Mellor

    Cement boards are ideal. Adhesive won't be an issue of the waterproofing, its literally what it's purpose is. But not sure why the XPS is there. I'd be concerned about that rather than anything else.

    Also, bare in mind that large format tiles are no heavier, per sq.ft or sq.m than smaller tiles

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  • Registered Users Posts: 6,570 ✭✭✭10-10-20

    It's probably these cement layered XPS boards. I used them instead of ply for floor tiles recently enough.

  • Registered Users Posts: 38,979 ✭✭✭✭Mellor

    I used “soft” board under floor tiles before. But for walls I always go with rigid FC. Although, the description say it’s fine for walls too.

  • Registered Users Posts: 6,570 ✭✭✭10-10-20

    There is less flex in these than 12mm plasterboard anyhow. I was impressed as they are easy to work with.

  • Registered Users Posts: 34 rymass

    That's exactly the ones I have 👍. I checked with the local building supplies store and they said the tiles won't fall off with the tanking membrane - As long as they are not extraordinarily heavy tiles. Mine are only 60cm X 30cm. But are floor tiles which I liked the design of .