Rust: building a door on a second story

I just made a second story to my base and i would like to put a door on the second floor from the stairs. But it does not let me place one.

Here’s a image http://gyazo.com/00a174cfdb11a0c6ced74743f430e730

Please help :wink:

If you stand at a 90 degree angle you should be able to place it

Thank you so much my good sir! and for the fast response <3 #RUST4EVER