Here's my latest addition - an isolated BUA which is a Farmhouse
Then I add the removable ruins - these are not strictly necessary, I just like 'em.
then I build up the shells around the ruin outline adding a basic card roof to be tiled later. Note I have already pencilled in the area to be taken up by the wall surrounding the BUA to make sure I can still fit in the bases.
I can be lazy at times so I added "stone cladding" from railway sheets
not forgetting the roof tiles - see elsewhere on this blog for details
add filler, paint & flock & you have a Farmhouse module