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1st Floor Make Up insulation

  • 18-08-2009 10:38pm
    #1
    redonly
    Registered Users, Registered Users 2 Posts: 25 ✭


    I have a 150mm prestressed wideslab on my first floor with my block work built directly on this and all the joints between the slabs filled in. I have 85mm to finished floor and I intend to do UFH with a selflevelling floor screed.
    My question is:

    How much insulation should i use?

    Would this be typical?

    50mm (xtratherm uf or similar) insulation and 35mm Easyscreed/floscreed or similar
    40mm (xtratherm uf or similar) insulation and 45mm Easyscreed/floscreed or similar

    any advice.....taking into account insulation/noise/cost etc..

    thanks in advance...


Comments

  • #2
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    Before you proceed any further - check with your structural engineer .

    1. Widelabs usually require a structural screed over and
    2. the blockwork should be built off this screed not directly off the wideslab


  • #3
    soldsold
    Registered Users, Registered Users 2 Posts: 555 ✭✭✭soldsold


    Would the structural screed be on top of (touching) the wideslab or over the insulation? My guess is connected to the wideslab hence the name "structural screed", but if on top of the insulation this would make a huge difference to sound isolation which would be a big advantage in my case.

    Steve


  • #4
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    The screed must be on top of the slabs . This is important so the entire floor construction knits together as one stiff "plate" . This is required for the overall stability of the overall structure . Wind forces will strike the extenal walls - they require to be braced by a properly designed and constructed floor structure .

    It is a BIG mistake to build the upper level wall of the raw slabs and "use the blocks as shuttering" - never do this except for -

    Some hollowcore installations ( deeper than 150 typically) can work " as plate" by simply grouting the joints BUT BUT BUT - only if designed and certified to do so by a structural engineer who is responsible for the overall structure . Simply talking to the precast floor rep will not cut that mustard .


  • #5
    redonly
    Registered Users, Registered Users 2 Posts: 25 ✭redonly


    Sinnerboy when the slab provider surveyed the house and plans we didnt know what kind of heating would be upstairs at the time rads or underfloor, So he suggested that we go with 150mm prestressed and build directly on them my engineer spoke to them about the spans and support so i asume thats right if not I am in trouble now!!

    (They were also talking about 100mm with a 75mm screed but decided against)

    Basically as you said grout the gaps put in insulation and then screed have you seen this done before?

    What is the certificate does this come from my engineer or provider (who is also an engineer)

    What is hollowcore?


  • #6
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    Hollowcore slabs have continuous hollows which you can see when you look at the end of each slab . Widelabs don't .

    You have an engineer - so maybe all is well . Involve him now (and lets know).
    "The certificate" is "the sign - off" the engineer gives when all works are done

    If all is well structurally then use 40mm insulation + 45mm "flo" type screed .

    I have done a grouted not screeded precast floor before ( with structural engineer designing and certifying ) - but in an office building with a raised computer floor not UFH .


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  • #7
    soldsold
    Registered Users, Registered Users 2 Posts: 555 ✭✭✭soldsold


    Anyone know if hollowcore or wideslab is better for sound isolation between floors?

    I need to decide soon which to go for, my engineer suggests wideslab for more thermal mass but sound isolation is more important to me...


  • #8
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    Hard to say . It depends on the mass - i.e. amount of concrete per m2 .

    Hollowcores - have hollows of course but are deeper than wideslabs .

    More important will be attention to detail - i.e. ensuring every floor penetration is properly sealed ( for fire and sound ) - bathrooms / elec / heating will all requires holes drilled .


  • #9
    redonly
    Registered Users, Registered Users 2 Posts: 25 ✭redonly


    Spoke to both engineer and provider today they have designed a system that does not need a structural screed. The slab i have is 150mm wideslab with steel and white aeroboard inside it, is this hollowcore?


  • #10
    Carlow52
    Closed Accounts Posts: 2,389 ✭✭✭Carlow52


    redonly wrote: »
    Spoke to both engineer and provider today they have designed a system that does not need a structural screed. The slab i have is 150mm wideslab with steel and white aeroboard inside it, is this hollowcore?

    In fairness what does it matter?

    Both products are similar in their construction methodology but wide slab is not hollowcore and visa versa

    look at profile here
    http://www.merseybeams.com/products/Wideslab/Wideslab-150mm-Wideslab.html

    and here
    http://www.oranprecast.ie/products_hollowcore.htm


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