The Purpose of a Truss
A truss is typically used to support the roof in a house. Because the roof is slanted and the truss must support the weight of the roof, it should be sturdy and structurally sound. The truss is designed so it provides support both vertically and horizontally to the roof boards.
Structure and Design
A roof truss is designed like a suspension bridge in one sense. It has a series of angled braces that extend from the center of the truss outwards at 45 degrees. These braces connect with the slanted frame boards that form the angled slope of the roof. They also connect with horizontal boards that provide the support for the bottom of the truss, as well as the top of the house's ceiling. This feature also provides a frame for the drywall in the ceilings. Each roof has one truss beam set every 18 inches along the frame of the house.
Bracing and Manufacturing
Trusses would not work at all if they weren't manufactured with a series of braces that help connect the supports to the main beams. A strong center support, which bears most of the weight of the roof truss, is often secured by four braces that attach to the sides of the center beam and both the top and bottom roof beams. Each secondary support brace inside the two main beams are also secured by angled braces and galvanized nails or screws. This helps keep the truss supports straight and reduces the load that otherwise would be carried only by the nails and screws used to secure these boards together.
Another facet of the truss is the slat boards that are installed between each truss support. Since there are many trusses set up along the house, and only anchors to hold them upright, a slat board that is about 2 inches wide and 3 inches thick, is connected between each one. In this way, the entire series of trusses are supported. Each truss provides linear support to the one next to it, creating a very strong support system. The roofing boards, when installed, provide the most linear support for the roof.