You cant make a unit type flyer to unable to fly over structures unless you use regions with triggers or pathing blocker for air.
Recommendation: pathing blocker is much easier.
Pathing blockers for air block the air pathing because of their pathing map.
You can set the pathing map for structures also.
If your building is a rather small building you can make it use the pathing map of the air pathing blocker and thus your building will block air pathing.
If it is a large building you can use the arcane observatory pathing map which also blocks air units.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory