An ordinary beam is part of a standard timber framing system in pitched roof construction.
A common beam is a building component used to build a pitched roof. These beams are made of wood and are part of a standard wood framing system. In a traditional gable roof, which features a triangular shape, the common rafters form the sloped sides of the triangle. Each roof is made of many common or general purpose beams. The number of common rafter units required for each project largely depends on the size and span of the roof, as well as the distance each rafter unit must cover.
Ordinary beams are joined at the base by ceiling beams, which run parallel to the floor.
Each common beam extends from the top of the building’s exterior wall to the peak or ridge of the roof. The rafters are joined at the base by ceiling joists, which run parallel to the floor. A series of small beams, or collar braces, is used to stabilize each pair of beams midway up the top. A single plate known as a ridge plate fits between the tops of each pair of rafters.
Builders rely on screws or nails to secure each common beam to surrounding structural supports. The top end of each joist is angled or vertically cut, allowing it to fit snugly into the ridge plate. The bottom of the common joist is often tapered to accommodate soffits and flashing. A special cut, known as a bird’s mouth cut, is used to allow the beam to sit snugly against the exterior walls.
It is important, when choosing a common beam, to calculate the correct length for each unit. Builders and installers can use a variety of tools to determine stud size, including online calculators and manufacturer charts. Most construction calculators also have a built-in beam sizing feature. In general, the length of the joist is a factor of the overall span or width, as well as the pitch or slope of the roof.
In many parts of the world, builders have switched from standard wood framing to prefabricated roof beams. These trusses feature a triangular shape, incorporating two common beams and a connecting roof beam. Metal plates and other fasteners are used to hold these components together. These common frame units often cost more than wood frames, but they also offer many benefits to homebuilders and homeowners. They allow contractors to build a roof much faster than traditional methods, which can reduce labor costs and shorten the project schedule.