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Insulating a bedroom floor above a garage

SuperHomes Revamp Forums General Discussion Insulating a bedroom floor above a garage

This topic contains 3 replies, has 4 voices, and was last updated by  Daniel Nestlerode 5 years, 6 months ago.

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    David Kerr


    My home has a bedroom above a garage, we are finding it very difficult to keep this room warm during winter. The garage ceiling is made of asbestos.

    It has been suggested to lift the floorboards in the bedroom and insulate between the joists as a means to help retain heat. I have been looking into this and understand that it is important that the insulation touches the bottom of the floorboards and that there is a space between the garage roof and the bottom of the insulation.

    Does anyone have any advice in terms of what insulation to use (boards, wool etc) for this?




    Hi my first thought was to fix batterns around the edges of each box section of the floor as low as possible then I though that might not be good idea. because of condensation forming on timber thus causing it to rot over time….

    Then again if

    Difficult to advise without knowing size of Timber Or what is supporting floor

    Have U thought of insulating above the floor using kingspan Type Insulation at least 4″ thick and to reduce heat loss from around the edges of wall insulate using Sheeps wool which I used to insulate under my front room floor it was hung from chicken wire.If U decide to go this way then I need to explain a few things …. Arnold superhome in chester



    Get the asbestos removed (or do it yourself – very carefully!).
    The best place for a polythene vapour barrier would be directly under the floorboards.
    Re-lay the floor.
    Fit between and under with PIR board, foamed in.
    If you do a tight job with the insulation, I don’t see why a gap would matter. It’s just a pocket of warm air. – But a gap IS BAD if you have other air-gaps to the sides of the joists, and cold air can circulate through to the warm side. This is probably why the advice to keep insulation touching the boards was given.
    The space beneath the boards comes from standard roofing practice, which is to allow condensation under impervious felt somewhere to go. 50mm gap is normal beneath ordinary old felt. (Less or zero if you have breathable membrane..). In this case it’s a garage, not a roof exposed to the cold night sky. Also the plasterboard you will re-line the garage with is breathable. – So I’d say the gap beneath was unimportant.
    Replace garage ceiling with standard fireproof plasterboard.


    Daniel Nestlerode

    I agree with Justin that the asbestos needs to go. You could disturb it by adding the insulation and that would kick fibres up in the air. Not good. Be careful with this stuff. (At Devana we turn down jobs like this because of the asbestos and the possibility of disturbing it.)
    Added benefit of removing the garage ceiling would be access to the space. You could lay up some batten or rolled type of insulation, like fibregalss, Rockwool, sheeps wool, etc. Put up a new double layer of plasterboard afterward and your job is finished. No real need to disturb the floor.

    A vcl is not a necessary addition to a floor unless you are looking for air tightness that is not provided by the insulation itself.

    Hope this helps!

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