Originally Posted by
DrDragun
Yep, as Hitman said, culture buildings are auto-demolished when you conquer. You can build human warriors from orc barracks, the only limitation is the Culture % in your settlement. If you are a good faction, I would recommend to demolish troll pens. It will give you money and delay the AI from building trolls if they recapture the settlement. Likewise, demo all stables if you are playing as the Dwarves. Basically, demo anything that you don't intend to use.
Culture handled differently than vanilla Medieval 2 Total War. It is not determined by having foreign buildings in the settlement. It is a value that is changed over time by the culture building at a fixed rate, and you can check it in the "Settlement Details" scroll.