Doubling up 50mm insulation boards

[LeeDowner]

I'm fitting some internal wooden cladding/panelling.

Behind it I have chopped out the plaster back to brick and I'm now going to insulate the wall before the panels go on. This particular corner gets mouldy every winter or else I wouldn't be doing the job, it needs insulation and the cladding is just a way to make it look nice.

I bought 50mm polystyrene boards but now these don't look thick enough to have a shelf on top of the cladding so I'm thinking of doubling them up. Does this create an issue with a potential air gap between the boards ?

Thanks, Lee.

 

[catlad]

How are you going to have a gap?
glue them together with expanding foam.

 

[geraldthehamster]

No.