"There are birds on top of the house."
Translation:Evin üstünde kuşlar var.
If someone asks you if there are birds nearby (or on top of the house) you can reply that way. It's all about emphasis. If you just saw birds on top of the house out of the blue and wanna inform someone about this say Evin üstünde kuşlar var. So, I think your example can be accepted too.
But the given translation can work in every situation, so it's better to put the subject just before var/yok.
If someone asks you '.... nerede var? (Where are there.....?)' you can reply it by putting the locative just before var/yok.
- Where are there birds? (Kuş nerede var?)
There are birds on top of the house. (Kuş evin üzerinde var.)
Where is there a supermarket? (Süpermarket nerede var?)
- There is a supermarket in this street. (Süpermarket bu sokakta var.)
However as I said you can always use the given form (Evin üzerinde kuş var and Bu sokakta süpermarket var.) So maybe it is better and safer to stick with the rule you talked about.
I think because the house gets the suffix for the possessor third person singular. The top of the house.... ev-in The cat of the woman.... kadin-in But I am a beginner. Maybe somebody else will answer you. If not start a new thread with your question, than you have usually a better chance that somebody answers, than in the middle of a 5 year old thread. ;)