On 06/05/2021 12:05, rick wrote:
On 04/05/2021 20:48, George Miles wrote:
I'm planning a small extension,
walls to be brick on the outside,
then a cavity, then blocks

The blocks hold the roof beams up,
the bricks are to look nice and stop rain.

I see videos of people putting insulation -
(wool or kingspan)
in the cavity.

But wouldnt there be a thermal bridge leaking heat both at the bottom
and the top of the cavity insulation?

Wouldnt the same amount of insulation be more effective if on the
inside of the block wall ?

george


Cavity walls came about to prevent damp in solid walls buildings.Â* 18"
stone was fine, single skin brick on 50s was the problem.

Filling the cavity gives insulation, but it has inherent risk of damp,
there are many claims of cavity wall insulation failures - it is fine if
done properly, but would not be my choice.

Can you not build with Thermalite blocks, they are fully load bearing as
long as you put suitable wall pate on top (standard practise) and
lintols with correct bearing over any openings.



If BCO is involved (and legally he has to be) then he will insist that
the construction complies with Part L anyway, which probably means
thermal block inner leaf and either 50mm PIR + 50mm cavity or 100mm
full-fill cavity with rockwool batts, then 100mm outer brick skin or
100mm blockwork to be rendered.