Fencing

Plywood warping after self levelling screed applied

Anonymous user 01/03/2024 - 2.37 PM

Hi, thanks for quick answers. I think we are more or less resigned to taking up the floor in these areas and re-doing with thicker ply. We had wondered if it were worth screwing down the warped areas or removing the screed in just these areas and rescrewing, but I anticipate the professionals reactions to this might be ones of horror and disgust ;). Not sure if we can get a 12mm in there as I believe we had just 4mm on top of the hardboard so may have to grade off where the two meet. Erm don't recall the Karndean supplier mentioning that we needed a vapour barrier or sealing the underside of the ply in the kitchen, I'm pretty certain it is just battens and then the ply boards but I will check with my husband. Thanks again. E x

Anonymous user

Not very wise to use self levelling compound over a suspended timber floor. Ideally you should have plyed the floor with a suitable 18mm WBP ply or even better marine ply. You will still get a few hairline cracks in the compound as with any timber suspended floor you get a certain amount of deflection over the span. With regards to the kitchen floor, which you say you laid 12mm ply on batterns which were fixed to concrete base... did you instal a vapour barrier between the concrete and timber/ply boards? and more importantly did you seal the underneath of the ply?

Answered18 July 2011

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Anonymous user

I think the problem is with the depth of the ply, it has simply absorbed too much water from the leveller and swollen. Take up the hardboard and ply, re-ply to the floor boards with the best depth you can, at least 12mm. use 30mm screws, Gold or galvanised, not bright metal or they will rust.

Answered19 July 2011

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Cannon Preservation Ltd

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Colchester

Hi Emma The moisture may have played at part in the problem and its great you have used plenty of screws(every 150mm would be good)But leaving the hardboard and using a very thin ply isn`t the way. If your limited for depth that you can use! then i would use at least a 12mm but if im honest you cant go wrong with a 25mm marine ply. With a tiled floor i would always use a 25mm but in your situation im positive the 12mm will be sufficient, as long as its screwed at 150mm centres and taking care that you dont use a screw too long as to puncture/pierce a pipe. Good luck. Scott.

Answered18 July 2011

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