The next dev blog will feature an in-depth piece on the current state of multi-floor, to quickly summarize it and not spoil too much we’re right now working on the core tech for building and visually presenting the different floors (i.e. rendering). and especially making important changes to the grid instantiation (noticeable loading improvement as it will start loading in the main menu already). Once we’ve fully decided on how to visually render the different floors we will then move on to construction simulation and path-finding. The number of floors we will support is as of yet undecided but at least a basement, ground floor and a second floor, depending on performance trade offs we might support a second floor but this is not by any means set in stone.
You will be able to build roads and conveyor belts on the basement level, yes.