Bitumen under upstairs bay window

[angliojoe]

Hi all,
I have an upstairs bay window that has bitumen painted underneath it (I assume to prevent damp) and then been wallpapered directly on top and it looks god awful. Its single skin so I want to insulate and board. Can I stick insulation directly to the bitumen with foam and then board and skim as normal? or should i try and remove the bitumen first?
Thanks,
Joe.

 

[tell80]

Why not post pics showing the inside of the bay (bitumen), & the outside of the bay?

 

[angliojoe]

the outside of the bay is render is a good state and the inside of the bay is painted black tar so i doubt there is a problem with damp. The window has just been replaced too so should be solid

 

[Deleted member 292770]

The trend years gone by was to paint bitumen ,followed by silver paint ,followed by a thin layer of polystyrene off a roll ,followed by wallpaper. It was an insulation/anti condensation thing of the past.
screw insulated plasterboard directly over it and skim. theres no need for pictures.

 

[Nige F]

the silver paint would have been aluminium primer