Gap in Floor - making a house on a slope

[Silviak]

Hokay, so I keep running into this problem when trying to build a house on a slope. My walls line up to the foundation without CFE. I've made the foundation outline the house, so I can keep most of the space below open for the basement level, and I'm trying to now tile the first floor. Except there's always this gridless gap in the center I cannot cover! I don't understand. The rest of it is totally fine!

I checked with buydebug when I noticed the issue, but it's not showing a spawner there (unless I needed to do that before said build?)

Picture below for references. How do I fix that?

[samoht04]

It happens when the floor there has no support. Put some walls under that area and you should be able to place floor tiles there. Once you remove the walls down there the support goes so don't remove the tiles - they will stay there though.

[Silviak]

Okay, great. Thanks Samoht!