Level a floor with underlay?

Discussion in 'Builders' Talk' started by oli80800, Sep 17, 2019.

  1. oli80800

    oli80800 New Member

    I have an uneven subfloor (floor boards). It appears to be higher in the centre and slopes downwards on either side. There are also other raised areas. I am planning to lay hardboard, then insulation, then electric underfloor heating and then engineered oak flooring.

    I am aware that I should be sanding / planing the raised patch in the room until fairly level before laying the hardboard. I am wondering if, instead, I can lay underlay on the lower parts of the floor in order to even it out.

    Anyone tried this? Any obvious reason to avoid this approach?

  2. DIYDave.

    DIYDave. Screwfix Select

    5.5mm flooring ply then self levelling compound would be one good method

    Quicker and more accurate than trying to level with bits of underlay here and there

    Your new oak floor will thank you for it :)
    oli80800 likes this.
  3. oli80800

    oli80800 New Member

    Thanks for the reply. Would the self levelling compound not escape at the edges of the ply? I imagine it would be a challenge to totally seal the flooring ply at the edges by the walls.
  4. DIYDave.

    DIYDave. Screwfix Select

    Lay the ply first to cover gaps in floorboards (for exact reason you mention)

    Any gaps around edges can be filled with expanding foam, allow to cure then trim back or simply caulk or ‘no nails’ type gun adhesive

    When you say gaps around edges, I take it skirtings have been removed ?

    Buy flooring ply 5.5mm x 8x4 sheets as works out best value, timber yard will further be best price and will deliver
    if needed

    Cut and lay as tight as you can on joints. Again, any gaps between boards can be filled as above (unless their tiny gaps)

    The self leveler goes down pretty runny so yep, will escape down gaps

    At door threshold, just screw a timber batten across doorway to act as a barrier

    Have you used SL before and/or you a competent diyer ?
    Last edited: Sep 17, 2019
    oli80800 likes this.
  5. oli80800

    oli80800 New Member

    Thanks for the info. That’s really helpful.

    Yes the skirtings have been removed. I have not used SL before but am fairly competent.

    Thanks again

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