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Discuss Advice on bathroom shower backer board and waterproofing installation in the Tanking and Wetrooms Forum area at

  1. Rich_O

    Rich_O Enthusiastic amateur

    Hi all, first post so apologies if I don't get my questions quite right and ask too many; I am looking for some advice on a new shower enclosure project.

    I am currently remodelling my main bathroom and plan to do most of it myself (except for the tiling.)
    I am a reasonably experienced DIY'er and can take on most construction, plumbing and fitting. I have previously replaced my ensuite shower, sink and toilet units so have some knowledge of what is involved.

    In the main bathroom I am putting a new offset quadrant shower cubicle in one corner which previously was dead space. In terms of structure I have removed the original plasterboard which takes me to breezeblock on one wall and wooden studs on the other. I will also remove the floorboards and replace with marine play for below the shower tray.

    My current thoughts lead me to board the walls with waterproof XPS boards, probably Jackoboard as I can pick these up from my local Jewson. The shower tray is a shallow one, approx 20mm depth and the shower controls are concealed in the wall cavity.

    My questions are these:
    1. Should I waterproof the marine ply?
    2. Should the backer boards go flush to the ply base or do I leave an expansion gap as you would for cement board or plasterboard?
    3. If I can go flush I assume I can then seal the whole system?
    4. Are there any tips ensure a waterproof seal around the fixings, joints and shower controls, other than the standard tape and fill with tile adhesive?
    5. The shower tray is a cast resin type, which recommends bedding in mortar, but I have seen advice that states tile adhesive is just as good. The ply base will be level and true, so any thoughts?
    6. I won't be tiling myself, but anything else in the prep I should think about?

    Lastly I am looking for a tiler to do this shower, behind the bath and sink, so any contacts in the Belper area appreciated.
  2. Localtiler

    Localtiler Trusted Advisor Professional Tiler JOTM Winner


    Hello Rich, in reply to your questions,

    Board the wall with the jackoboards down to the ply, doesn't matter about any expansion gaps, tape the corner joint with self adhesive tanking tape, or seal with jackoboard sealant, or the tray directly onto the marine ply with a good s2 adhesive such as tilemaster ultimate, then seal the tray to the wall using the sealent.

    The floor will need boarding anyway and jackoboard is good for that. I can't see any reason not to board the floor before fitting the tray and make a seal behind where the tray is going to go then stick the tray to the jackoboard rather than the plywood, unless some one knows otherwise?

    You can get pre cut circles of self adhesive tanking tape which might help you seal your pipe holes
    • Like Like x 1
    Last edited: Aug 30, 2017
  3. impish

    impish Trusted Advisor Professional Tiler

    As above really.
    I'd add that Jackon make a product called BoardFix and it's identical to Schluter's Kerdi-Fix. Elastomeric sealant / polyurethane / leak-proofing - BOARD-FIX - Jackon Insulation -
    If you are accurate enough with your cuts and holes, this product will seal everything up. I would also join the boards together with it in your wet area.
    The principal to remember is to use the Board-Fix to join foam to foam, but if you need to join cement faces, you will need to tape those and use something like Ardex WPC.
    To be honest though, in a domestic wet area, as long as you are accurate, you could use just board-fix with the jackoboards and it will protect you well enough.
    • Like Like x 1
  4. Localtiler

    Localtiler Trusted Advisor Professional Tiler JOTM Winner

    Im 20 miles from Belper.
    • Like Like x 1
  5. bolts

    bolts Active Member

    in responce to :

    1. Should I waterproof the marine ply?

    I'm not sure if you mean the whole floor or just below the shower tray ?
    If correctly fitted and sealed the area below the shower tray should be the dryest part of the room. The only place you could then have an issue with is the shower waste which in your case must be below the floor so waterproofing the floor would not help if it leaked anyway.

    I have removed showers which had been in place 20ys + and if the shower tray and waste have been sound then the place you usually see water damage is just outside the shower at the edge of the shower tray, which is where the most water is likely to spill.

    You should be ok as your shower should have doors, if you were fitting a shower with just a screen on one side then I would take care to waterproof and seal the floor area beyond the edge of the shower tray as the floor is likely to get a regular soaking.

    Hope this helps, good luck with your project.
  6. Rich_O

    Rich_O Enthusiastic amateur

    Thanks for the responses. Just to clarify that the ply will only go under the shower tray, plus a bit to extend to the next joist for fixing.

    I hadn't planned to put backer board anywhere on the floor as I'm not tiling it, probably will be vinyl tiles and current floorboards are sound enough for this. But it sounds like a good idea to seal the ply anyway as it can't harm and may help with the area immediately outside the tray.

    So based on the advice from the three kind folks above I think I will do the following unless someone shouts "NO!".

    1. Walls with Jackobard, seal all joints and holes as per manufacturer instructions and bring down to meet the ply base.
    2. Waterproof/ seal all of my plyboard and it's edges. Tape seal joints between wall and floor.
    3. Fix shower tray to ply using flexible adhesive and seal/fix tray vertical edge to wall boards.
    4. Pay special attention to shower waste sealing.

    Any advice on which product is best to seal and prime the plywood base?

    Thanks again.
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