I always make a solid 'foundation' first meaning: that they get the blue overlay. Even wooden flooring should pop blue and not just the green. With a strong foundation, I find you can go quite a few units up green until it enters 'yellow/orange' stage, then I completely stop building and support it again.

I also find that stone&iron is really great for beginning a new 'foundation'/blue for further construction. I suggest trying to get to 'stonecutting' as soon as you can, really helps with fortifications. I find the building system really interesting and well thought out, just needs more art/pieces...even with the provided units, some really varied constructions can be achieved. Just follow the 'rulez', lol.....Blue Foundation, Green constructions, keep away from Yellow-->Red overlays. You can get pretty creative with supports/foundations[blue constructions]

It does act strange sometimes: I have an angled beam accent from a X piece at the center of a pass thru. On this angle extension, I have a metal sconce, directly under this is a workbench. I cannot determine what causes the angle beam to become destroyed as well as the sconce. I'll return after some time to find the components sitting next to the bench and the dock?? Thought perhaps a random Dwarf tossing rocks/large ocean swells or something not allowing this construction to stay intact. I can never figure out what is causing it, so I just leave it off??