Interior Balcony Question

[Lysamus]

Hello all. I'm attempting to build an interior balcony on a 2nd floor. When I use the foundation tile to designate space for the balcony, it creates an opening in the roof. It looks like the only way to seal it is to use wall tiles. I'm using archway tiles to do so but I was wondering if there's another way to do it other than lining the balcony with arches. I'm currently still in the Act 1 area if that helps.

Thank you in advance!