Good advice, hazelrah.

The build system does somewhat work like a real building would, you have to make sure things are stable otherwise it won't work.

You can frame the floor, roof, and walls with support beams before actually building a floor, roof, and walls. This can make it really easy to snap the walls, roof, and floors in place. Takes more resources but usually makes a stronger building, and it's usually less frustrating if you aren't used to the system.

Like I said, I've seen some pretty huge builds using just wood so the system is robust and you can do a lot with it once you get used to it.