(Deleted by user)

I found a good way to make an upstairs room, delete the floor, and still make a landing for my stairs. Go ahead and delete the whole floor. To build a new one, select your deck options, assuming it's completely flat, lay it out the way you want. It creates the floor, no glitches (that i've experienced). you don't have to worry about building something just to delete it, and you can build walls all around it. It really works out great for me.