Gap between 2nd floor balcony and room below

[josjg]

Hi,

I'm new to HD and have this problem when I try to create a balcony on the 2nd floor. Going through the forum I managed to solve most of them, but one remains. There is a gap between my balcony and the room below. See attached pictures.
I have used normal railing instead of deck railing and named the balcony "balcony" I've tried to manipulate the floor and ceiling heights of the room below and the balcony, but the "floor Structure" remains set at 318mm whatever I do. And the gap remains. How to solve this?

Jos Gielen
Home Designer Suite 2014