Thanks for all the interest and comments.
To answer a couple of questions:
Lovely stuff. Where did you get the trusses from?
I drew them in TinkerCad and 3D printed them. To be honest I could have just cut them from card as they're not exposed on the final model, but I find it easier to let them print out while I do other things.
Did you use cloth material for the canvas, I have thought about doing that but can't figure out how I would stop the threads coming out or manage to glue the material tautly given its inherent floppyness.
Yes, I used plain cotton. I made a simple hem on the material by folding it over and sticking it down with PVA. I find that if you press it down the PVA comes through the cloth and makes a good bond. Just means you have to work out the panel size and hem it before you apply it to the building.
Vagabond - I think they whole thing was dipped in a water/PVA mix and then put in place to dry.
I tried that but it got really messy.
The method I use now is to glue the dry hemmed cotton to the trusses using gorilla waterproof PVA, then when that's dried I apply neat PVA in small amounts to each panel then work it into the fabric with a very wet brush. This has the benefit of 'stretching' each panel and getting the sagging effect. Just by chance the brush I used for this model had some brown paint in it so it created a dirty effect which will help with the overall finish. I'm going to add a bit of brown paint to the next lot I make too.

I’d wondered how you were going to incorporate removable roofs into your tented builds.
So did I

. I actually applied the canvas to the roof and sides as one piece, fixing the roof in place. Then when it had dried I got a razor blade between the roof base and the top of the wall and cut it round. Worked better than I'd expected.
If anyone's interested I'll have a go at a 'How To' next time I do a roof.