The brick bit is dated 1961 (it's been written into the door step while it was still wet), the oak is marked on the ends of the beams with Roman numerals, which means it's been moved from somewhere else (paint before assembly...) so is presumably older. Probably a lot older
I'm not really sure how to go about it. I have planning permission to renovate it, so demolishing it and building something modern is out of the question. A lot of the oak beams have had it, particularly towards the bottom. The brick, although the mortar looks quite iffy, seems to be fairly solid. The sides of the loft space are meant to be quite open as it's meant for storing hay for winter feeding, there's even a fair pile of hay up there.
The brick part is in fact a pigsty (I'm planning to use it as a workshop, so I guess it'll always be a pigsty

) with rotten boards over a concrete floor.
What I'd like to do is keep it looking fairly similar, although obviously I'm not going to replace the oak, and I'm certainly not going to do anything with that amazing roof, apart from change anything rotten and replace the missing tiles. But I don't like the idea of having to dismantle it to replace the walls.