Room is a unit of area equal to 144 square feet or 16 square yards, meaning when formed in a square would have the length of 12 feet on all sides. Since 12 feet is a string, the room unit can also be called square string. Hence the unit term, it is about the area of a typical-sized bedroom. The area of an average home is about 15 rooms, sounding like it's referring to the 15-room home, but it doesn't necessarily have to contain 15 rooms in order to have that 15-room area. Over the years, the average area of the newly built homes increased from 11.5 rooms all the way up to 18.6 rooms.