@Dives:
Rafters are not too thick at all. Most old houses are built with such dimensions in sweden/norway and other places I'm sure. Since the supports you have are so big, and since this is a game level, I'd put them underneath instead of on the side (just looks right
). The span of the rafters (from wall to wall) is small enough to be self-carrying (if that is a word =P ). The supports from your reference image has been carved slightly out of to sit below the actual rafter (hard to spot). But for the sake of visuals, I'd also put them right underneath.
Rafters 1 inch thick is waaaay to small and would not hold the weight at all. 1 inch = 2.54 cm, which is the dimension of the woodwork used as battens for cosmetic construction (roof tiles, woodboards on the outside walls etc). You could make use of it, but you'd need a much smaller span between them.
You'd need atleast 38 x 140 mm, every 60cm set up like so:
As his house somewhat mimics older houses, his dimensions looks rather good when the span between the rafters seems to be 80cm'ish (they would need to be bigger then):
Anyway, enough technical; I love this map! It looks great, and the level of detail is fantastic!