Concrete flat roof insulation

11 Aug 2010
Reaction score
United Kingdom
Hi, our bungalow was originally a flat roof building, which has since been extended and had a pitched roof fitted.

All the extended area is insulated. The area with the concrete roof has not been insulated. The concrete roof is six inch thick concrete on top of wooden boards and beams and if course has the pitched roof over it now.

Is it worth insulating the area covered by the concrete flat roof? I would have thought the concrete would be enough but of course I don't know enough about it. In the summer on really hot days it stays nice and cool so I assume the opposite in winter?

Sponsored Links
Concrete U values aren't easy to calculate as it depends on the mix. It could be between 0.75 and 3 depending on the mix. Is it very cold to the touch?
You could look at the roof to see if its not covered in frost during a cold spell, that is a give away of a poorly insulated loft.
Sponsored Links
If I'm understanding you correctly and you have built a pitched roof over a concrete flat roof? then you can lay Celotex/Kingspan on the top of the flat roof and just weigh it down with a few old bricks.
Last edited:

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