How much gap under a terrace wall coping stone when using external cladding

[alayton]

Hi , I am having Cedral Click installed on a wall that goes up to a terrace.

I was thinking of using a flat slate lintel/coping stone on top of the terrace wall  but Cedral requires ventilation and a mesh profile so i am wondering how much of a gap under the coping stone I will need (10mm seems to be mentioned in the context of a soffit.) and also how much the coping stone should extend away from the wall to stop water ingress.....

 

any comments or advice ?

[Mr Punter]

I have used the aluminium copings with overhang on clad walls which works well as you don't see the ventilation gap at the top.  20mm overhang.