Surface covers Nuclear Storage Building

Issue description

After I changed the surface under my nuclear storages, the surface is covering the stairs of the building.
I tried to delete the surface, but it does not work.

Reproduction steps

Place a nuclear storage.
Change the surface under it.

Game version and build number

v0.6.4d(b343)

Operating system

Windows

This also happens, when u place a new nuclear storage on a floor with any surface.