Houses are built on land. Though there might be houses built on other things that are on the sea or suspended in the air in developed countries. In my country, most of our housing structures are on land. There are many different types of houses on the land. The type of house people build is dependent on the nature of the land.
Many landscapes in my community are usually flooded with water. Despite this, people still look for ways of raising their houses on such land. What could make them go for such types of land when building their houses is because that is what they have. Landed properties are owned by different people. So, it is what belongs to you that you can build on or you acquire other plots through purchase.
Building on the water-logged lands used to be stressful. Most times, some of the houses collapse. Those who survive are built with lots of materials. Raising buildings in water areas used to incur a lot of materials.