Machines can only be placed on solid flooring — stone path, concrete, refined concrete, or any other high-speed tile.

Works correctly across all planets:
- Nauvis — lay concrete before building
- Gleba — shift-build automatically places concrete ghosts on natural terrain
- Aquilo / Vulcanus — water and meltable tiles require landfill or equivalent first
- Space platforms — treated as solid flooring, no concrete needed

Stone and steel furnaces are exempt so the early game remains playable. Electric furnaces require flooring.

Forked from Buildings On Concrete by Zenyatta11. All credit for the original concept goes to them.