A hut, for example, is defined as a modest structure with one or two rooms, typically built of wood, mud, grass, or stones. It is also termed a primitive housing because it is built with indigenous resources such as grass, mud, and wood. In more developed countries, huts are usually made of concrete or steel. Nigerians have used trees to build houses since before the arrival of Europeans. The Igbo people were said to be masters of building architecture. They used to build their houses with wood and thatch, and sometimes with cement. When Nigeria became independent in 1960, many buildings were constructed using European design standards. These include the house style known as a "northern hut." This is basically a rectangular building with symmetrical exterior walls made of mud or stone. There is a hole in the roof through which smoke escapes but not much heat. The floor is made of clay or dirt. There are several different designs of northern hut. They are commonly found in villages where there is no electricity or good roads. Northern huts are very efficient at keeping out the rain and wind. They can also be heated with a fire inside a stove placed inside the house. Western Huts are similar to northern huts except they have wooden frames instead of only mud or stone walls. Western huts tend to be taller and have more rooms than northern huts.