Originally posted by Bohemian Rap City:

Make sure all the beams have direct line to structural support (shaded blue) elements. If they turn yellow they are weak and cannot be added to without more support.

Close , yellow can be built on red cannot. But that's an issue of structural integrity not weather damage.

For regular wood it's something like 8 or 9 points of contact between ground and the piece you are adding before it turns red. There is only one shade of blue(ground) but a couple shades of green, yellow, and red.

Horizontal beams, flying buttresses (perhaps some application), it matters not. Just count the connections from ground.