Single leaf 'Celcon' wall.

[AllexMyers]

I am replacing a pitched roof (Marley tiles) above a porch with a sloping roof (same tiles) butting the house wall. The side walls of the porch are concrete block inner with stone outer and not insulated (so probably a U value of around 1.0). By changing the roof layout I will have a triangular section each side to take the existing wall up from the lower end (gutter) to the wall plate. I am thinking of UPVC shiplap to finish the outside (not wanting to cement more stone in place). My idea is to use insulating blocks (say Celcon 440x215) stretching across the cavity at the top of the existing walls and having plaster inside and batten against the new blocks to fit the shiplap finish. I am not thinking of an insulating layer here just using the blocks to stretch across the existing walls (about 300mm) with of course space for the shiplap, probably about 60mm allowing for battens. This wall takes no load and the triangular section is only 2300mm base and 750mm height.

The edge of the roof will be Marley edge tiles which come over the outside wall (shiplap).

Will this construction suffice as a way of avoiding cementing concrete blocks? thanks for your time here.

 

[23vc]

The cavity wall overall width must currently be wider than 215mm surely?
I wouldn’t lay them flat, assuming that’s what you mean. I’d match the cavity and insulate it. If it’s being clad you might get away with celcon outer skin but I’d use a lightweight concrete block, you can get ones that aren’t very heavy

 

[AllexMyers]

The cavity wall overall width must currently be wider than 215mm surely?
I wouldn’t lay them flat, assuming that’s what you mean. I’d match the cavity and insulate it. If it’s being clad you might get away with celcon outer skin but I’d use a lightweight concrete block, you can get ones that aren’t very heavy

The walls are 100 inner 50-70 cavity and 120 Purbeck stone uninsulated (can't insulate irregular block walls). So I am planning on laying the blocks lengthwise across the cavity leaving space for plaster inside and battens outside. Maybe you are suggesting a layer of insulation under the battens and fixing them to the blocks through the insulation?