yes some of the building takes a bit to understand.. in the shortest possible explanation foundations when placed.. if you hover over them and wait a bit they will stay blue. (ie good!) whereas walls and roof sections once placed start off blue then after a while if you hover over them or wait and watch.. they change thru to red sometimes and then after red they collapse.. (this is relative to how far from foundation they are..ie higher closer to red)
Also adding "normal" ie irl bracing does nothing to help in fact the opposite often where the additional load on walls etc turns them red (ie use hammer and hover over them) there are many detailed explanations of using stone iron etc in a construction in here. sadly i dont have those links any more some one may post them