Outhouse utility

[Gem844]

Hi,
Turning a single brick outhouse into a utility room with toilet . It is single brick and just wondering in terms of installation what would you do:
1) Battens with insulated plasterboard?
1) Frame, Insulate then plasterboard?
Would it need a vapour barrier? Heat source would be an electric radiator only.
(Floor is concrete)
Or any other suggestions. Thanks

 

[oldbutnotdead]

Insulated pb is much more expensive than insulation and pb.
So frame, insulation between battens (whatever depth you have) then more insulation (another 25 or more mm) over the top to get somewhere near 100mm total then pb. If you foil tape the over the top insulation that'll be your vapour barrier
EDIT If space is tight, you could use external insulation on the wall(s) you have external access to.