Rigid floor insulation

Discussion in 'Builders' Talk' started by Simon Bishop, Nov 4, 2020.

  1. Simon Bishop

    Simon Bishop New Member

    Hi all
    I'm looking to insulate a concrete floor slab.
    My thoughts are a damp proof membrane, solid insulation boards and ply on top.
    The floor will have some gym equipment on - can anybody recommend a good type of rigid board that would take the weight?

  2. Jord86

    Jord86 Screwfix Select

    Put joists down and cut the insulation in between, then flooring on top.
    rogerk101 likes this.
  3. Simon Bishop

    Simon Bishop New Member

    Thanks. Even with joists there would be areas of insulation on it's own, but I guess the joists would help to spread the weight?
    I would prefer not to do joists but am concerned on getting the correct boarding
  4. jonathanc

    jonathanc Screwfix Select

    Rigid insulation then t and g chipboard laid as floating floor should be fine
  5. Simon Bishop

    Simon Bishop New Member

    Thanks. Any recommendations of particularly good rigid boards?
  6. rogerk101

    rogerk101 Screwfix Select

    I strongly recommend the joist approach, as the alternative (floating floor) requires a dead flat concrete base, and I don't know of any self levelling screeds that can achieve that.
    If you really don't want joists, then you should use 22mm chipboard with T&G all round, and then each and every T&G joint glued really well with Gorilla (or other) glue. The idea here is that the whole floating floor becomes one solid 'tectonic plate' that sits on top of the insulation. You'll still get bouncy hollow areas which won't be great for a gym, but would be ok for a living room.
  7. John9857

    John9857 Member

    Yes, use Danosa XPS. This is a lot stronger than PIR. Its thermal value is not as good but if you are going to put gym equipment on top of it I would not use PIR. Danosa XPS is easily bought online at good rates.
    Regards, Build4less

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