I recently saw foundation building block bug on my server, and because I made foundation invulnerable using Indestructable Buildings. It just detects if there is a foundation on top of the position you try to build on and removes new entity if it match foundation.
With this new plugin, your player will not be able anymore to build an invulnerable house.
With this new plugin, your player will not be able anymore to build an invulnerable house.