Can not place floors or walls

[AlbinoBandito]

I have been running into an issue where I am unable to place floors or walls when in certain areas. If I am on the ground I am able to place the walls and floors. but if I go up one level, two stairs, I am not able to place anything. This issue started about a week ago and have not been able to find a solution for this since it began. 

[AugspaCussh]

Does the error message say "unsupported" or "obstructed"?

 

If the pieces are "unsupported" there is a way to trick the game into letting you build there: place column blueprints from the ground (or floor) to the spot you want to build your new floor. Having the column blueprint won't instantly let you build, but it will let you place the floor blueprint. keep placing floor blueprints around it until you get to a wall or other structure. Build the piece that touches the wall (since that should be enough to make it 'supported'), then build all other floor pieces outward from the first. Now just destroy the column blueprints and you should be good to go.