Room/Doorway Ceiling Material

[Chief-007]

Hello,

I was working on a model and ran into an issue. I have 2 rooms with different material finishes, when I added a doorway I realized half of the doorway took the ceiling material of room A and the other took the material of Room B. When I spray paint it so its all material B in the doorway, room A ceiling changes (material is connected to room ceiling). Is there a way where the doorway only takes the material of room B? Why does it take half of the material from room A and the other from Room B?

Thanks in advance.