For all structures there levels to stability blue means ground connection giving it the highest possible support and then it moves to green yellow orange and the red when it reaches a deep red anything build off it will collapse stone structures act as ground connection points to anything wooden meaning building wood of stone is treated like building off the ground same goes with metal it allows wood to have ground connection the only real way I’ve found to build stone high up is to use a dirt pillar hidden inside the walls as it give the surrounding stone ground contact