I plan to redevelop a porch into a toilet, where the porch is located
under the original roof (i.e. it has an existing recessed front door).
As a result, I will create a new external front wall, and plan to remove
the external brick skin of the existing porch to maximise toilet
dimensions (all structure is supported on the internal skin).

Above ceiling height, as the then single skin internal wall will be in
the roof void, I wish to add insulation to the wall. I am considering
using something like 200mm of Celotex or equivalent.

My question is, how would one attach the Celotex to the single skin
wall, and to what extent is vapour sealing required (membranes?).

Is there anything else I should be aware of?

Thanks in anticipation
Paul R

On Mar 3, 2:40 pm, Paul R wrote:
I plan to redevelop a porch into a toilet, where the porch is located
under the original roof (i.e. it has an existing recessed front door).
As a result, I will create a new external front wall, and plan to remove
the external brick skin of the existing porch to maximise toilet
dimensions (all structure is supported on the internal skin).

Above ceiling height, as the then single skin internal wall will be in
the roof void, I wish to add insulation to the wall. I am considering
using something like 200mm of Celotex or equivalent.

My question is, how would one attach the Celotex to the single skin
wall,

low expansion polyurethane foam

and to what extent is vapour sealing required (membranes?).

seal the joints between insulation sheets with same stuff as above (or
foil tape if you're paranoid) and you shouldn't be far wrong.

NB technically should probly come under Building Regs..

Jim K