doors?

I was hoping someone could explain to me the purpose of the doors. Inside the masters house/temple there are two doors that seperate the prayer area from the masters sleeping area and the guest's sleeping area. There are no walls but everyone seems intent on using the doors. There is also a door that meets the lake with no surrounding walls. In one scene during summer there is a sick guest who is sleeping in the guest area and the boy in the opposite room wants to lie with her. He is sleeping beside the master and goes to open the door but he can't open it wide enough because the master is sleeping next to it. He instead steps over the master walking around the door into the prayer area then continues to ignore the door into the girls "room". Is this a common thing in Korean culture? Is it supposed to symbolize something other then a division of space? Thoughts, ideas?