Roof is the topmost element of a structure. It is the only element that does not carry a load and is instead carried as a load by the structure. The stability of the roof may sometimes be associated with its mass. The more massive it is designed, the more stable it attaches with the structure and the stronger it resists uplift forces. Nonetheless, a massive roof can stress the structure roughly to even cause it to collapse. The ideal roofing system is light but strong.
Since roof must be light enough for the structure to carry, it is designed with trusses to make it a hollow object but with maintained sturdiness. Trusses are framed rafters composed of tendons that seize resistance against uplift pressures.
Trusses are responsible for holding together all other parts of the roofing system through its systematically arranged tendons. They can either be made of metal or wood according to the architectural requirement of a structure. Most roofing companies in largely industrialized cities like Omaha construct prefabricated trusses for structures they roof. Prefabricating the trusses ensures quality control.
The tendons of a truss are carefully arranged in such a way that vector forces are exerted evenly. For example, the pitch (middle tendon) must have an upward force equivalent to the sum of the downward forces of the opposite rafters (inclined tendons or top chords). Some trusses don’t have a middle tendon instead two inclined tendons connected to the peak and exerting a resultant vertical force. Most Omaha roofing companies design rafters and pitch with well-bolted connecting plates to ensure stability along the joints.
Other tendons of the truss such as the prop and the collar tie are added to support the rafters in case additional load is applied, for example, when the roof sheeting is put in place and the workers hammering it on the lateral joists. Omaha roofing companies who prefabricate trusses adjust the number of tendons according to the type of roofing materials to be used.
For example, if the roofing material is slate, more tendons must be connected in order to support the weight, unless the roofing system is composed of steel truss, which normally has very high stress tolerance. This is the reason most roofing companies Omaha NE has redesign the trusses before changing the type of roofing of a house under remodeling.