help with laminate moving and dipping when walked on

Discussion in 'Wood' started by Julie Irwin, May 12, 2022.

  1. Julie Irwin

    Julie Irwin New Member

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    Hi I helped lay click laminate in my daughters lounge which is dipping in 3 or 4 areas when walked on.
    The house was built around 1940 has a concrete floor with a thin layer of bitumen and then floorboards laid directly ontop. One small section of floorboard approx 18" in the corner of the room had rotted which we replaced and in the doorway a couple of the floorboards were dipped in the middle and raised at the edges. We ensured all the floorboards were secure by nailing down before we started laying the 7mm fibreboard sheets which we though would be better at levelling the surface where needed. (I now realise I omitted to leave the 2mm gaps in between the underlay sheets and only noticed this when re reading the instructions and in some places didnt leave the expansion gaps at the walls as I didn't realise the fibreboard can contract and expand).
    When watching people walk on the floor it can dip for 2 feet or so around the area trodden on.
    The flooring was only laid 5 days ago and we are going to lift and start over. I have bought an electric planer to take the edges off the couple of raised floorboards and am wondering if I need to put plyboard or osb board down on top of the floorboards if so what thickness would be required, or can the issue be caused by the underlay being too tight, or as I've been advised by a flooring supplier today maybe I've used the wrong type of underlay?
    Any advise please, as my daughter is on a budget and cant afford to get a fitter in.
     
  2. tarkett85

    tarkett85 Well-Known Member

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    You nailed through the dpm oh dear god, rip everything up, remove ALL of the bitumen, proper surface dpm and new screed then put the laminate down on an underlay with a vapour barrier not fibre boards that’s an expensive mistake.


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  3. tarkett85

    tarkett85 Well-Known Member

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    I forgot to mention that’s only if the concrete which happens to be around 80 years old now is still in good enough condition after you remove it all, there’s a high probability after that amount of time a new sub-floor is required modern concrete usually lasts around 50 years if well maintained.


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  4. Paul webb

    Paul webb Well-Known Member

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    I bet you're glad you asked now, one possibility could be, if there is no expansion gap somewhere (only has to be one or two spots),the floor may have expanded, causing it to raise slightly. Is the movement more on the joints or are the boards bending?
     
  5. Julie Irwin

    Julie Irwin New Member

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  6. Julie Irwin

    Julie Irwin New Member

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    there was a row of nails in the floorboards already and thought we were nailing into a joist at the time. when you say rip up and put a dpm course down would that be thick plastic sheet typeyou can buy from screwfix etc, or wondering if i put down marine plyboard would that act as a damp proof course in itsself or ok to lay plyboard or osb board ontop of the plastic sheet membrane ?
     
  7. Julie Irwin

    Julie Irwin New Member

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    hi there is an expansion gap around the edges of the laminate but not on the fibreboard underlay, and its more that the boards are bending
     

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