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Concrete floor slabs

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  • 14-09-2019 11:44am
    #1
    Tiobkuhi
    Registered Users Posts: 17 ✭


    Hi all

    Looking for some advice. Builder putting upstairs insulation down. Joints between concrete slabs still visible. Should these be filled with mortar to help with sound/fire etc even though a screed on top of insulation?

    Thanks in advance.


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    #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Not necessarily. *Screws on top of insulation will take care of that, gaps between pc concrete planks should be minimal - your eng will inspect for TGd part A and arch for TGD part B

    Separate question: How did you deal with air-tightness at external wall junction?

    Edit: screed*


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    #3
    mickdw
    Registered Users Posts: 23,281 ✭✭✭✭mickdw


    What is the floor structure. Did the slab manufacturer call for the joints to be grouted?
    Consult your engineer before the insulation works proceed.


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    #4
    Tiobkuhi
    Registered Users Posts: 17 ✭Tiobkuhi


    BryanF wrote: »
    Not necessarily. *Screws on top of insulation will take care of that, gaps between pc concrete planks should be minimal - your eng will inspect for TGd part A and arch for TGD part B

    Separate question: How did you deal with air-tightness at external wall junction?

    Edit: screed*

    Thanks Bryan.

    Slabs sit on inner leaf, with taped full fill rigid insulation. Row of insulation cuts vertical to external wall and taped....I think.


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    #5
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Tiobkuhi wrote: »
    Thanks Bryan.

    Slabs sit on inner leaf, with taped full fill rigid insulation. Row of insulation cuts vertical to external wall and taped....I think.

    Sorry wasn’t very clear. How are the pc concrete slabs air-sealed at the perimeter junction with the external wall air-tightness layer ?


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    #6
    Wartburg
    Registered Users Posts: 134 ✭✭Wartburg


    Tiobkuhi wrote: »
    Hi all

    Looking for some advice. Builder putting upstairs insulation down. Joints between concrete slabs still visible. Should these be filled with mortar to help with sound/fire etc even though a screed on top of insulation?

    Thanks in advance.

    I´d highly recommend to close all joints and penetrations, to achieve a good air tightness and sound proofing. If you just rely to the screed on top, you still have the upstanding insulation to the walls as a potential risk for transfering sound, smell and (worst case scenario) air. The attached photo shows a small part of the floor slab for upstairs, where every joint and penetration has been filled with mortar. Bigger pockets where backed with expanding foam before applying the mortar. This detail, in conjunction with a comprehensive air tightness strategy, brought the house down to 0.56 ACH @50Pa differential pressure on the preliminary air tightness test prior the second fix. The house was build with a 200mm cavity, to be filled with beads.


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    #7
    landcrzr
    Registered Users Posts: 150 ✭✭landcrzr


    Precast slab joints should always be grouted. It helps transfer shear loads between slabs.


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