So I live in Canada, where winters are cold, and where there's not much soil above the bedrock. I would like to build a sturdy structure for an existing "shed" (in fact a 100-year old former stable or something) that's about 4m by 5m (12'x 15') and that's kind of collapsing. Currently, there's no real structure to speak of: it's only 2-inch thick boards piled up and nailed together, with small posts (like 2x4s) in the corners, resting on slabs of cement or something, each one about half as big as a basketball.
There's only about 60 cm of soil above the (granit) bedrock, and I was considering pouring concrete "posts" to rest directly on the bedrock, then using them as a basis for my structure (placing a metal plate on top that I can put a wood post on). My neighbour says that in the spring the meltwater will accumulate over the bedrock and may damage the concrete posts. Also, I would guess the ground probably freezes down to the bedrock in winter.
Any thoughts about this? alternative solutions? Note that I don't want to take the shed apart because it's 100-year-old wood and I think I would inflict substantial damage to it.