Roofing and Building Center

Basic Roof Truss Information

Posted on December 11, 2009 by Samuel Cheeseman

A roof truss is a structure usually found within the pitched roofs of many kinds of buildings. They are most often triangular in shape and form the foundation of the roof which all other roofing materials are laid upon. The primary function of a roof truss is to distribute both dead and live loads around a structure in order to spread their weights and reduce the stress put upon any one area of a property or its roof. Dead loads are the weight of stationary components such as the roof trusses themselves and other roofing material such as roofing shingles. Live loads are usually capable of movement and often natural such as wind, rain or snow.

Roof Truss Varieties

There are many common roof truss designs which will suit nearly all roofing projects. Occasionally a highly specialised roof will require a custom design and this will be reflected in the roof truss prices. The triangular shape is extremely strong and effective at transferring any stress throughout the structure to the walls on which the trusses rest. This design has many advantages over using flat roofing. The triangular shape of a pitched roof is structurally far stronger than one which is flat or nearly flat. The risk of damage or collapse due to heavy rain or snow fall is reduced to almost zero as the shape lets excess water escape efficiently rather than accumulate on the roof.

Timber roof trusses are common in all types of properties with pitched roofs. They provide a solid structural framework while the truss is protected from the elements by the roofing materials it supports. This prevents any damage to the wooden structure. Steel roof trusses will also sometimes be used which are as strong as a timber frame. Commercial roofing projects are more likely to use steel roof truss plans than residential ones in conjunction with the metal roofing often used in commercial or industrial properties. This is partly due to the size of these buildings being considerably larger meaning metal roofing will be more suitable.

Roof Truss Failure

Although expert roof truss design ensures that they are very strong structures a truss can fail on rare occasions. This is most common in older buildings. Building roof trusses is a complex skill which is usually only undertaken by experienced professionals and any failure will rarely be due to mistakes made during roof truss construction. It will sometimes be caused by careless workmen drilling or cutting into them while working on electrical, heating or other systems and not understanding the structural important of the truss and the stress it is under.

The most common causes of wood roof truss failure are snow and more frequently, water damage. Water leaks resulting from rainfall or melting snow can cause damp conditions which will over time penetrate into timber roof trusses. This can also affect timber which has been treated, but not right the way through the wood. Damp will often cause timber to rot and may encourage insects into the wood roof trusses which will lead to further damage and weakening of the structure. These problems will be more severe in older roof trusses where wooden pegs have been used to fix individual parts together rather than screws, nails and glue as used in more modern buildings. Where the wooden pegs are damaged the joints can eventually fail which result in serious structural damage to the roof and maybe a total collapse. Where roof truss damage has occurred it can sometimes be remedied without dismantling the roof. Roof truss repair can however be very dangerous due to the weight of the roof being supported by a weakened structure. An experienced structural engineer should assess the damage before you decide to take any actions to repair roof truss rot problems or replace a roof truss.

Roof trusses are an essential component in virtually all roofing systems. Providing a solid framework which will support other roofing materials while at the same time spreading their weight, the truss will provide stability and security to the whole roof. They have proved extremely useful for many years and will continue to do so in the future.

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