Installing insulation below a floor slab– screed and concrete?

Discussion in 'Builders' Talk' started by Rhaegar, Feb 16, 2019.

  1. Rhaegar

    Rhaegar New Member

    I have a question about installing floor insulation. The previous concrete floor failed due to a lack of DPM and has now been removed. Is it possibly to lay a new insulated floor without a concrete slab, using only floor screed? For example:
    1. Level layer of hardcore
    2. Layer of sand blinding
    3. Damp proof membrane
    4. Jablite 70 floor insulation (100mm thickness)
    5. Vapour control layer
    6. Screed (1.4) at a thickness of 4" inches
    Is it better to install insulation below a concrete floor slab and finish with screed, or above a concrete slab and then apply a screed finish?
     
  2. Jimmycloutnail

    Jimmycloutnail Screwfix Select

    Insulation above slab and screed on top
     
    rogerk101 likes this.
  3. Rhaegar

    Rhaegar New Member

    Thanks for the reply. Would that require two layers of DPM? For example:
    1. Level layer of hardcore
    2. Layer of sand blinding
    3. DPM
    4. Concrete slab at a thickness of 3" inches
    5. DPM (?)
    6. Jablite 70 floor insulation (75/100mm thickness)
    7. Vapour control layer
    8. Screed (1.4) at a thickness of 3" inches
     
  4. stevie22

    stevie22 Screwfix Select

    It is better to put the insulation under the concrete (which wants to be 100 min) because:

    1. Nice thermal reservoir
    2. Only need 50 screed
     
    Rhaegar likes this.
  5. Jimmycloutnail

    Jimmycloutnail Screwfix Select

    That make up is how we would do it and the current way it’s done mainly due to the rise in underfloor heating where the pipe work is clipped to the insulation and screeded over, but as steve has said concrete meets to be 4” and 65mm screed.
     
    Rhaegar likes this.

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