If you are wondering what is a duplex house, then you've come to the right place. Duplexes are multi-family homes that are divided into two parts by a wall or floor. They are common in various countries including the UK, and are particularly popular due to their affordability. This type of property can provide you with a large number of benefits, including less money spent on building and maintenance. There are a few differences between duplexes and townhouses, however.