A truss roof is a load-bearing structure for the shape and support of a roof's frame.
A roof truss can be made from a variety of materials including wood or steel. Some common types of increasingly popular trusses include the below.
This truss includes sloping rafters joined by an upper horizontal piece, forming an A-frame. Box truss is also known as the “king post truss” style. This "king post truss" design is used in many barns and sheds throughout America today. The king post truss roofs include the bottom chord, king post, etc. and are mostly used for basic projects.
Horizontal beams that run the entire span of the building project with shorter vertical pieces crossing them at regular intervals to form triangles that carry much more weight than simple rafters. This truss are usually found in large, multi-story buildings. The truss is formed with bottom chords, struts, top chords, etc.
A box truss that uses two horizontal beams with a smaller beam across the top forming an X shape at each intersection. The beams used here are straining beam, tie beam and collar beam. Queen Post Truss is also known as the “priest” style. This queen post truss was popular during Victorian times for its aesthetic appeal but does not carry weight as well as other types of trusses like the king post truss.
This truss consists of 3 triangles where each is formed by 2 diagonal rafters and one central vertical post (or king post). These roof trusses are most commonly used to make attic roofs for gable ends (the triangular section of the roof frame between the eaves and ridges). These roof trusses and tie beam can also be used to provide additional bridge-bracing and support to a simple rafter roof. Top chords and bottom chords are used to form the ceiling truss.
This consists of 2 triangles joined at the hip (hence the name), usually by an additional diagonal piece. This trussed roof design is used in buildings where several large areas come together, such as churches with multiple wings, vaulted ceilings or living space. The hip truss also provide support for longer spans than other scissor trusses, making it useful in wide-open spaces such as attic warehouses and garages roof frames. Some other types of roof trusses available include fink trusses, attic trusses, scissor trusses and many more other types of truss which are made of timber or steel.
Roof trusses and rafters are both load bearing structures in a typical roof pitch. The main difference between the two is that attic trusses are custom built from pre-cut pieces of timber, while rafters must be cut on site to fit each individual house building site. Roof trusses may also be used as part of larger buildings such as warehouses and barns. A truss can provide support to the weight of different floors and provide additional bracing for more complex purlin roof designs. Top chords, bottom chord, struts and many more components are used to form the ceiling truss. This makes roof trusses more appropriate than roof rafters for large open space areas where equipment or mechanical devices may need to be housed or transported.
The costs associated with installing either roof trusses or rafters on job site will vary greatly depending on the material(steel or timber) used, the part of the country in which trusses are being installed, and whether or not a professional structural engineer or construction labour is being used. Trusses can cost considerably more than rafters for multiple reasons: They must be cut to fit each individual building construction site. The materials used to make roof trusses such as nails, wood glue, and metal connectors add to their overall cost because they do not grow on trees. Also, there are usually many complex joints that need additional maintenance beyond what a simple rafter requires. This costs money in both time and materials for ongoing repairs/maintenance. This results in higher installation costs of tie beam and roof truss. Because a professional installation is needed in most cases, the costs for this service must be included in the overall price of installing the of roof trusses. In contrast, roof rafters or ceiling joists may cost less than attic trusses because they can be cut from any kind of timber available and do not require the same level of precision to fit correctly onto interior walls or gables. This means less span and materials are required during installation of rafters. There is typically much less craftsmanship involved in installing a simple rafter vs any complex design rafters that utilizes multiple pieces. This results in lower labor costs when hiring a professional of construction industry to install any type of roof truss. When considering which system to use for your next building construction project, consider the overall cost that will be associated with it both upfront and long-term. Are you looking to simply replace an old roof truss or do you need a more permanent solution that won’t require countless repairs? If you are considering installing multiple types of roof trusses such as Queen Posts and Hip Roof Trusses, keep in mind that these queen post structures can become quite complex and time consuming. You may want to put more of your budget toward simpler options such as a rafter roof or stick built roof.
Gable end trusses feature one or more triangular ends that meet at an apex (the peak between two slopes). This type of truss is often used to support the vertical loads of walls between two angled roofs known as a gable.
A roof truss will last for long span if it is properly maintained and constructed to adequate construction and building codes. This means that you should construct your truss out of treated timber or nails with a high rating for durability. You can also reinforce the roof structures using metal connectors and fasteners such as galvanised straps and steel plates.
If you know that your roof truss requires repair, then it is likely that there are already signs of structural damage present. These signs can include:
Gaps at the joints where two pieces meet.
Broken or cracked wood in the internal structure of the root truss.
Sagging under added weight over time.
Leaks due to water damage, wind loads or rot on some part of your structural framework.
Replacing one or more roof trusses can be a complex task depending on the type of roof truss you have and whether or not it is possible to remove some parts of the entire structure of roof truss without damaging other components of the vaulted ceilings. In some cases, you may need a professional who has experience installing your specific kind of roof truss. If this is not an option due to budget constraints, then you can try removing the roof trusses by hand using crowbars and timber blocks as leverage against nails and joints on the roof truss itself.
In most cases, replacing a roof truss will require at least one additional person aside from yourself for safety purposes. If you are attempting to replace an entire roof framing system including rafters, this stick framing can become quite dangerous even with assistance. For this reason, it is nearly always best to hire a professional for this type of roof truss work. The Australian Building Codes Board has a great guide to understanding the different types of gutters available and their features.