I'm having a hard time taking enemy held structures due to not knowing what type of order is best. I generally have a very chaotic situation with the pathfinding. I'm wondering what I could be doing better, or if an explicit (Assault Building" order might be needed.
I found that only once I had destroyed all the enemy in the position or they had fled could I enter the building. A few sappers to batter down the doors please! The French spent the day try to get into the farms.
You have to engage them with musket and artillery, so line for infantry is best to bring the maximum firepower to bear. Use the artillery to lower the defensive bonus of the fort, cause casualties and lower enemy morale. You won't know the current damage level of the fort but fires will start if you pound it long enough.