It seems that colonists can build structures right over the top of the things that should block them. After construction is complete, I don't recall if they mine the nodes/chop the trees/clear the debris on their own, or only if I desigate those tasks. I've so far replicated it with trees, mineral surface nodes, as well as stumps and other debris. It's pretty simple to replicate. 1. Find some Flat terrain that has junk on it. 2. Designate a building over the top of the junk 3. Watch as the colonists use eldritch powers to bend the laws of physics to their will! Save and screen attached.