Is there a way to build over open air tiles?

Hi! I’m currently holed up in an apartment tower from the “Trapped on Rooftop” start. I’ve got a lot of supplies so far and have been wanting to expand the apartment outwards.

The problem is I’m on the second to top floor and the way I want to build is over open air tiles which won’t let me construct wooden flooring on them. Do I need to build from the ground up first or am I just doing it wrong or am I just able to not do that. Any help would be appreciated! Thank you!

There are no constructions that could be built on top of open air. It is possible to add them though.

In the meantime you can build a vehicle. Aisles make a pretty nice bridge.

Thank you for the replies! Yeah I might try the aisle idea! Thank you!