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No more ply, hardibacker or wedi/marmox - which is best for wooden floor overboarding & why?

Bathroom floor to be overboarded prior to tiling.
18mm boards have been replaced with 22mm exterior ply so little deflection.

Which backerboard is best in this situation - which would you use & why?

PS Not a wetroom


3 Answers from MyBuilder Tilers

Best Answer

Are you having any form of underfloor heating going down? If so it is probably worth tanking the floor and taping the joins, putting down the underfloor heating then latexing before tiling.

If you are just tiling then go for some of the waterproof flexible matting that all good tile stores will stock, usually on rolls and either yellow or orange, make sure you adhere it with suitable tacky adhesive which the supplier will recommend and using a 3mm notched trowel for best results. This will also keep the level of the floor down to a minimum for you.


Answered 18th Nov 2011

In this situation either marmox/wedi or hardibacker boards would both be suitable. No more ply is essentially the same as hardibacker they are both cement based backer boards. Marmox and wedi are the same stuff just different brands with nearly identical specs. If you are planning on using underfloor heating then marmox/wedi option would be best as it will insulate the floor and improve the efficiency of the heating system. Other wise there is not much in it, the installer may have a preference for ease of use but both of these options are preferable to a ply overlay. If the 22mm ply is fixed well to the joists and hasnt got excessive deflection then you could tile directly onto it without a backer board so long as you use a 2 part adhesive or a single part S2 adhesive like bal fastflex or mapei S2 mono.
good luck!


Answered 21st Nov 2011

Detra, this product will allow your flooring breathability,moveability and a stable foundation no matter prior flooring,once down floor tile or board as directed, ie normally.
best of look


Answered 20th Nov 2011

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