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What Are Roof Trusses?

A roof truss provides support for a roof.
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  • Written By: Charity Delich
  • Edited By: Bronwyn Harris
  • Last Modified Date: 23 September 2014
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    2003-2014
    Conjecture Corporation
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Roof trusses, which are structural components of houses or commercial buildings, support the weight of roof timbers and coverings. Usually, they are constructed from pieces of timber or steel which are nailed, bolted, or pegged together to form a mutually supporting and strong base for a roof. These trusses should never be removed or altered without the advice of a structural engineer. Unsanctioned changes to a truss could result in part – or even all – of a roof collapsing.

Typically, roof trusses are used in residential and commercial construction as an alternative to conventional stick roof framing. Using trusses instead of stick framing can provide builders with several advantages. For example, most such trusses are conceived by engineers, who have ensured they meet roof load and building requirements. By using prefabricated trusses, builders can significantly reduce their total construction time.

Another key advantage to using trusses is that of cost. Roof trusses are generally made from two by four stock. This stock is significantly less expensive than the longer framing pieces used in conventional stick roof framing. In addition, trusses can usually be installed by less experienced carpenters, allowing builders to save on labor costs.

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When roofing a building or home, adhering to a proper roof truss design is critical. If one component of a truss is removed or weakened, the entire roof could give way. The design must take into consideration the strength of the timbers, if a wooden truss is used, or the steel, if a steel truss is used. Other factors that are important in roof truss design include the distribution of the load through the truss parts and the connection of the parts.

Roof trusses are available in a variety of shapes and sizes and can be customized to suit virtually any roof design. One of the most common types of truss systems is a pitched truss, also referred to as a common truss. Characterized by its triangular shape, a pitched truss is often used in residential homes and storage buildings. Pitched trusses include a host of specific truss designs – from double fink, attic, bowstring, and fan to scissors, double bobtail, and inverted shapes.

A number of factors can contribute to weakening roof tresses. Water leaks are one of the top sources of roof tress damage, particularly in older buildings. In wooden roof trusses, water leaks can lead to decay and insect attack, even if timber has been treated. If an electrician or a plumber cuts notches or drills holes in a roof structure, this may also weaken the tresses. Older roofs can be susceptible to joint failure if they were connected with Mortise and Tenon joints and wooden pegs.

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Logicfest
Post 3

Roof trusses can also be darned attractive if done right. Quite often, churches will leave those exposed, stained and treated -- it gives a very "old world" look when done right.

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