We have had two walls removed to open into an extension (340x320cm) and to add french doors to the extension. We face 2 issues:

  • The dining room floor is at a slightly lower level to the kitchen either side of the now gone wall.
  • The floor does not reach the door because of the cavity. (And also its slightly lower level than the door)

My thinking is to lay 22mm chipboard sheets over the dining room floor and screw them into the subfloor boards. Where these reach the door my thinking is have them overhang the cavity as it is only a small gap they should be ok anchored into the existing floor?

Is there a better approach?

Photos: enter image description here enter image description here

  • A better photo of that gap would be great. It's hard to interpret from above, and I'm getting dizzy.
    – isherwood
    Jan 20, 2020 at 20:37

1 Answer 1


I'm not sure what "chipboard" is, but your plan is ok if you use a structural sheet material (OSB or plywood). The span across the wall void is wide enough that you should find a way to support the sheet at the far side, though, or it's likely to flex a fair bit.

  • I've always thought that chipboard was OSB, but I've never been quite sure, and I don't know what they would call particle board... Good to get clarification.
    – JPhi1618
    Jan 20, 2020 at 20:52
  • Something like wickes.co.uk/…. What if join them with a c16 stud on the underside which will sit in the cavity? Hopefully make it a little more rigid?
    – Kiee
    Jan 20, 2020 at 21:48
  • Floating lumber underneath won't help unless you attach the lumber. Concrete screws or construction adhesive would probably work.
    – isherwood
    Jan 20, 2020 at 21:57
  • Chip board is made from pieces has pieces about 1cm / 0.5" in length OSB is made from has pieces about 15cm / 6" in length, but otherwise yeah both are made from wood fragments.
    – Jasen
    Jan 21, 2020 at 8:35
  • What's the actual industry term for "chip board"? I'm having trouble finding a reference.
    – isherwood
    Jan 21, 2020 at 13:49

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