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Is it feasible to achieve an airtight, insulated floor with T + G?

  • 06-03-2008 09:07PM
    #1
    ircoha
    Closed Accounts Posts: 2,290 ✭✭✭


    While most ground floors these days are concrete, there is still a demand for the nice spring of a wooden floor and the look of varnished T + G.

    My current design for this is to use flooring grade chipboard as the airtight layer over the joists after the insulation has been fitted.

    The theory is that if the air does get in between the insulation and the chipboard, at least it wont have an easy passage though.

    Then the T + G, which inevitably shrinks somewhat, is just really decorative.
    All comments welcomed.
    Thanks


Comments

  • #2
    gsxr1
    Closed Accounts Posts: 3,167 ✭✭✭gsxr1


    ircoha wrote: »
    While most ground floors these days are concrete, there is still a demand for the nice spring of a wooden floor and the look of varnished T + G.

    My current design for this is to use flooring grade chipboard as the airtight layer over the joists after the insulation has been fitted.

    The theory is that if the air does get in between the insulation and the chipboard, at least it wont have an easy passage though.

    Then the T + G, which inevitably shrinks somewhat, is just really decorative.
    All comments welcomed.
    Thanks

    The T + G will shrink 5 %. that for sure.

    When I have used it on new builds I have had problems with the stuff.

    Since the moisture level in the house is so high the T +G first starts to dish as the timber expands. Then 4 weeks after the heat get turned on it shrinks.

    the dish stays in the board and gaps form between them. It needs a whole lotta sanding to get the dish out of the boards.

    Some people love this effect.
    As for air tightness I don't know. I would think air would get in at the joints of the chip board. Im sure the engineers on here will know of a system to prevent this.


  • #3
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    ircoha wrote: »
    While most ground floors these days are concrete, there is still a demand for the nice spring of a wooden floor and the look of varnished T + G.

    My current design for this is to use flooring grade chipboard as the airtight layer over the joists after the insulation has been fitted.

    The theory is that if the air does get in between the insulation and the chipboard, at least it wont have an easy passage though.

    Then the T + G, which inevitably shrinks somewhat, is just really decorative.
    All comments welcomed.
    Thanks

    I would at least place a polythene layer directly below the boards . Possibly omit in the utility , where if the washing machine pukes up you don't trap that discharge .

    years since I have met this one - usual demand is to replace old timber floor with highly insulated conc floor , UFH and engineered timber ( or tiles )


  • #4
    Mellor
    Registered Users, Registered Users 2 Posts: 40,259 ✭✭✭✭Mellor


    gsxr1 wrote: »
    Since the moisture level in the house is so high the T +G first starts to dish as the timber expands. Then 4 weeks after the heat get turned on it shrinks.

    Well that is easily avoided by only putting the timber into the house one the RH of the house is suitable. Thid apples to all timber and not just floors.


  • #5
    ircoha
    Closed Accounts Posts: 2,290 ✭✭✭ircoha


    Mellor wrote: »
    Well that is easily avoided by only putting the timber into the house one the RH of the house is suitable. Thid apples to all timber and not just floors.

    Which is another reason why I like the OSB or chip or ply 'subfloor' which can be used for all the finishing work and then put the T+G down as final.

    In terms of engineered timber as alluded to by SB, I like this stuff for flooring joists.

    http://www.ilevel.com/floors/default.aspx

    Known as TJI also here and carried by James McMahon. http://www.mcmahongrp.com/
    there may be others.

    They only carry the flooring stuff here, the roofing applications are equally good.

    What I like about it is no dwarf walls for most domestic apps, just floor hangers and mininum 'noggins'.


  • #6
    gsxr1
    Closed Accounts Posts: 3,167 ✭✭✭gsxr1


    Mellor wrote: »
    Well that is easily avoided by only putting the timber into the house one the RH of the house is suitable. Thid apples to all timber and not just floors.


    this is true. But ..

    Builders like to get the T&G down before the first fix starts up stairs. It keeps costs down as the whole first floor can be knocked out quick . With full lengths of t&g being layed down without cutting around walls later.

    Not a perfect way to do it, but it is common practice. Especially when on a tight finishing schedule


    As for the engineered joisting. That would be a welcome change in the industry. 9 by 2 joists shrink . Causing real problems with upstairs tiling cracks and skirting gaps


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