Roof Trusses | A Definitive Guide | Aber Roof Truss

A Definitive Guide to the Inner Workings of Roof Trusses

Definition of Roof Trusses

 A roof truss is, put simply, a triangulated system of interconnected structural components, which are often referred to as open web girders. These components are connected and pinned via the nodes, with external forces and reactions at the supports also being applied at the nodes. When all of the components within the truss and the relevant applied forces are in the same plane, creating axial tension or compression, this effect then creates a functioning roof truss.

Roof trusses are a rigid and strong framework which is made from wooden members, like 2” x 4” these are then fastened and held together by metal connector plates. The framework is accountable for your roof shape and for supporting the materials of your roofing. Roof trusses are designed according to geometric principles that have been fine-tuned over thousands of years. In fact, many of the bridges that you will drive over in your car will use these same principles as a timber roof truss system.


How are wood roof trusses superior to conventionally-framed systems?

All roof systems should have truss design according to suitability for purpose – designed, constructed and installed in order to adequately meet criteria. Unfortunately, many systems do not meet the criteria. We believe that wood trusses are superior, thanks to their professional design, high quality materials, and the fabrication techniques.


How long do roof trusses last?

Roof trusses, including attic trusses with the right treatment, replacement of (shingles, and flashing) should survive the entire lifetime of the house, so long as there are no disasters eg. fire.


What holds a wooden roof truss together?

High quality metal connector plates hold the wooden truss members together. Their holding values and strength has been determined through years of extensive laboratory testing to ensure their integrity and durability.


How safe is a wood trussed roof system in case of a fire?

Fire is a hazard that can’t be ignored for any building system, and there has to be some meticulous safety procedures to prevent and immediately deal with a fire.

The way that a truss system is designed means that they do not necessarily depend on each other for support. In this instance, a truss might burn and even completely collapse, and yet it will not affect other portions of the roof. This means that there is an allowance of additional time to evacuate a building.


How are wood truss systems inspected for quality?

Usually council inspectors will inspect all parts of the building for integrity. This includes wood trusses. Roof trusses will have to be designed with these regulations in mind in order to pass.


Further Insight into Truss Structure

 In your average single-story industrial or residential property, trusses are incorporated to serve these two primary functions:

  • To bear the load of the roof – Gravity plays a big part in the trusses ability to hold the roof load (self-load, equipment, snow, wind).
  • To provide stability – Wind girders and vertical bracing in the side walls and gables.

The lateral stability of the properties structure is provided by the truss itself, through the components connected between the truss and columns. For the longitudinal stability of the properties structure, a wind girder is used, together with bracing in the side walls. This allows some of the load to be transferred from the truss and gables to the side walls and foundations.


 Roof Truss Shapes

There are a large range of roof truss shapes to choose from, that provide both structural and aesthetic benefits to properties:

Pratt Truss – A Pratt truss utilises diagonal members that bare the tension of gravitational loads.

Warren Truss­­ – A Warren truss also incorporates diagonal components are in both tension and compression.

Fink Truss – This type of truss is more commonly found in residential properties, rather than industrial.


There is still so much more to learn about roof trusses. If you require further information on roof trusses and how they can benefit your property, do not hesitate to contact the Aber Roof Truss team today.