Detect if connected to other builds

I'm making a fortnite like building game, and I have the building part downpacked, but now, the player can build in the middle of the air. I need someway to detect if I'm part of a build, or in the air. I already have a system that uses a trigger collider to detect if it's touching another build, but it's not working correctly. I though of using OverlapSphere, but that didn't work either. How can I do this?