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Laying Floor insulation on a rough slab

  • 09-09-2011 6:47am
    #1
    Caruth
    Registered Users, Registered Users 2 Posts: 2 ✭


    I am shortly going to lay Kingspan or equivalent insulation on a precast slab and the put UFH and screed it. The area is fairly big (about 200m2) on various split levels. The spec on the precast slabs was that they didn't require a structural screed and that they should have a reasonable finish so that we could lay insulation directly on them - they didn't arrive to spec. While the oveall floor is level as it should be, the slabs are probably too rough to simply to place board on top. To be specific the surface of some slabs have a slight bow (higher at the edges than the middle) and others don't sit flush against each other. The imperfections are not bad and when you walk into a room it's not very noticable but when you lay rigid insulation you notice. I don't want to have to screed the slabs or use leveling compound simply to get a flat surface before putting down the insulation (its too expensive for this size an area) and wondered if there is any issue with putting a thin layer of loose dry building sand or finer dead sand between the precast slabs and the rigid insulation boards. The sand would give me a flat surface on which to lay the insulation. I expect that the sand thickness will average around 10mm but in some areas will be a bit more or less.

    Any advice appreciated.....

    Thanks
    Tagged:


Comments

  • #2
    Poor Uncle Tom
    Registered Users, Registered Users 2 Posts: 14,547 ✭✭✭✭Poor Uncle Tom


    If you were told the slabs would be level enough to put the insulation directly onto them, and they are not then, personally, I would use levelling compound and try to off-set the cost somewhat against the slabs, which didn't do what it said on the tin.

    I wouldn't use a sand to level as when the sand dries out over time and with use it will dust up. You could end up with dust getting through slab joints and ending up with sand everywhere except where it should be.


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