I'm a first timer, so be gentle
I am planning a side extension with a vaulted ceiling. See images: first from inside, second from outside.
Inside the side extension, I have set the exterior wall (from main house) as plasterboard for both the 1st and 2nd floor - the 2nd floor was trickier, but I managed it if you see the second floor picture above.
The problem can be seen in the first photo. The interstitial space (is that what it's called) shows external brickwork - not plasterboard. I tried using the material eyedropper, the result is plasterboard coloured brickwork.
Can anyone help? Do I need to make this scenario clearer?