If you decide to build your own house rather than buy one already built. You must first select a lot or piece of land. The next stop is to consult an architect, who will design the house according to your ideas. The way a house is built depends on the style of house and on the kind of materials chosen. The architect may also supervise the actual construction of the house. First, building workers begin digging holes or trenches for the footings, the lowest part of the foundation. The footings support each wall load. They are made by pouring concrete into wood or steel forms. With the foundations ready, the builders start building basements which are situated within the foundation below the first storey. Basements add to the cost of building a house, but they provide extra room. Next, outer walls may be made up of layers of bricks, or of a wooden frame. The roof seals the top of the house. Some roofs are flat, but most are slanted.