A simple rafter roof consists of rafters that the rafter foot rest on horizontal wall plates on top of each wall.The top ends of the rafters often meet at a ridge beam, but may butt directly to another rafter to form a pair of rafters called a couple. Depending on the roof covering material, either horizontal laths, battens, or purlins are fixed to the rafters; or boards, plywood, or oriented strand board form the roof deck (also called the sheeting or sheathing) to support the roof covering. Heavier under purlins or purlin plates are used to support longer rafter spans. Tie beams, which may also serve as ceiling joists, are typically connected between the lower ends of opposite rafters to prevent them from spreading and forcing the walls apart. Collar beams or collar ties may be fixed higher up between opposite rafters for extra strength. The rafters, tie beams and plates serve to transmit the weight of the roof to the walls of the building.
A person that specializes in roof construction is called a roofer.
In the United States, regulation of the roofing trade is left up to individual states. Some states leave roofing regulation up to county-level and municipal-level jurisdictions. In California, for example, the California Contractors State License Board licenses and monitors roofing contractors. Unlicensed contracting of projects worth over a set threshold may result in stiff fines or even time in prison. In Oklahoma roofers are required to meet insurance and roofing license guidelines. Roofers are also required to show their license number on their marketing material.
The construction of a roof is determined by its method of support and how the underneath space is bridged and whether or not the roof is pitched. The pitch is the angle at which the roof rises from its lowest to highest point. Most US domestic architecture, except in very dry regions, has roofs that are sloped, or pitched. Although modern construction elements such as drainpipes may remove the need for pitch, roofs are pitched for reasons of tradition and aesthetics. So the pitch is partly dependent upon stylistic factors, and partially to do with practicalities.