When building a duplex, many things can be the same as when building a granny flat. The design can look similar to some facilities, but the only visible difference is the typical house. As for the design and facilities, you can conclude: • symmetrical design – a duplex-type construction is, in general, more imposing and has a pleasant appearance; • shared facilities – duplex houses can be separated or have interior (kitchen, gym, living room, etc.) or exterior (terrace, pavilion, swimming pool, etc.) areas both families can use.