Insulating garage conversion

25 Nov 2013
Reaction score
United Kingdom
I have an integral garage in my house with a bedroom above.
The garage has just had an asbestos ceiling removed and is now back to bare joist and the floorboards of the bedroom above. I want to convert this garage into an extra bedroom and include an ensuite bathroom also.
The bedroom above is quite cold and I would like to insulate the garage ceiling as the first part of the conversion.
My question is: should I use something like loft roll like Drytherm or maybe something rigid such as Kingspan.
The joists are 180mm deep, 350mm gaps, and include an electric cable for the garage ceiling light which I would keep for the bedroom.
Any advice appreciated..
Sponsored Links
I can't see the point of insulating the ceiling of the garage if you intend converting it to a habitable space, which doubtless will need to be heated. Surely it would be better to allow some heat leakage into the bedroom above, which you say is cold.

Fair enough if you intend removing the insulation when you do the full conversion but otherwise I can't really see the benefit long term. If you do insulate and leave it in there the bedroom above will still be cold.
I see your point.
Is that normal practice to not have insulation between ground and first floors so heat can rise through ?
What about sound insulation ? The room above is a teenager bedroom and with the normal music playing could be heard easily in the room below ?
The idea is to insulate the envelope not individual rooms. In a standard house configuration the living area downstairs will be warmer than upstairs so some heat leakage to upstairs will warm those rooms. Loft and wall insulation should then hold the heat within the envelope but insulating between floors would just mean having to turn up the heat in the upstairs rooms so it is generally not done.

Sound insulation is a different animal as sound transmission is carried by the structure and air so different principles apply. To be fully effective you have to 'disconnect' the structures you are trying to insulate from sound transmission.

Otherwise just give the teenager a clip round the ear and tell him/her to turn it down :eek:
Sponsored Links
yes, turning it down would be easiest however it doesnt last !! :confused:
I cant do anything about the structure being connected but maybe something to help with the sound through the air would help reduce the noise transmission. Is that the same as the insulation or is there other solutions...?
I'm not an expert in sound insulation but it is generally denser than thermal insulation as I understand it. Some say that packing thermal insulation tightly into a space can have a similar effect but it will have little or no thermal value as you have compressed all the air pockets (which are what actually provide the thermal insulation quality).

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local