Cold Bridging in Flat Roofs

Cold Bridging in Flat Roofs

Hi Steve,

The metal will not get “colder”. It can only get as “cold” as the ambient temperature it is “contact” with. Sorry, about the three replies, but I wanted to address each point separately.

That I beam, is at the top of the roof, near an exterior wall, with no “top load” (of significance) and appears to be acting like a ledger, for the roof rafters and ceiling loads. But, it also appears to not be supporting the ceiling below (appears to be a gap between rafters and ceiling).

Either way, the point is, keep the barrier on the heated side of the “insulation” or you will be putting your dew point in the insulation in the this “detail”.

Oddly, the “heated side”, could, in fact, be the roof side and NOT in the inside of the house depending on temperatures of your drawing’s location (in the world and daily mean temperatures).

Also, more consideration should be given to venting all roofs.


In England, we put the vapour control layer the warm side of the roof we also don’t vent our warm roofs.



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Comments (2)

  • Kevin Brend Reply

    Hi Steve.
    Installed 5 en-suites in a property to be told they are having a single story extension!… issue is that the flashing is smack in the centre of all the 110mm horizontal pipes.
    Would it be poss to run x2 timbers parallel and hang roof joists off of that structural timber.. enabling a box gutter to be fitted against the main wall. One side of the box would be lower so a flash line can be cut and lead dressed over.. and the other side higher and bolted to the x2 timbers?

    4th April 2023 at 6:18 pm
    • Steven Dickinson Reply

      sorry for the late reply I get so much spam on this that is really hard to find the real people who need help. However I’m here now if you need help still please just email email me speak soon

      19th August 2023 at 8:55 pm

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