Extension Insulation Detail

[carson3221]

Hi,

I am having a return fill, single storey rear extension built, removing the existing rear wall (orange) apart from a pier either side to take the beam over the new opening. How do I detail the continuity of insulation around these pier details in a way that will satisfy building control? Existing building is 50mm full fill mineral wool cavity, new extension is 150mm full fill mineral wool cavity.

What is the best way to prevent the thermal bridging effect where the new wall abuts the existing walls? Do i need to be concerned about any possible condensation from bridging of the external brickwork from the 1st storey where it sits on the new beam?

 

[23vc]

Bottom left and right - inner skin’s already got a thermal/moisture break due to the cavity
Top right - cut a groove and put a vertical dpc in.
Above roof - retro fit a cavity tray.

Personally I’ve built one without doing either of those, BC was fine, and zero issues as expected in a decade. But it’s how belts and braces you want to go, and varies by area/weather exposure etc.