A Roof is one of the most important components in building construction. It is what keeps us protected against the outside elements. There are different kinds of structures to consider when building a roof but today we will be discussing the use of timber for roof trusses.
What is a roof truss
A roof truss is a structural framework of light steel or timber designed to bridge space above a room and to provide support for a roof.
The truss is one of the basic types of structural frames formed from structural members. A truss consists of a group of ties and struts designed and connected to form a structure that acts as a large span beam. Trusses usually occur at rectangular intervals.
General uses for roof trusses:
- Achieve long spans.
- Minimise the weight of a structure.
- Reduced deflection.
- Support heavy loads.
Roof trusses are typically made up of three basic elements:
- A top chord which is usually in compression.
- A bottom chord which is usually in tension.
- Bracing between the top and bottom chords.
The top and bottom chords of the truss provide resistance to compression and tension and so resistance to overall bending, whilst the bracing resists shear forces.
A little bit of history…
Before the invention of the truss, roofs were limited to a certain size. Then came the truss, providing load-bearing strength over large spans. With a few angled cuts and axial tension (or compression), the truss broke this deadlock for spanning roofing distances.
The word “truss” actually originates from an old French word trousse, meaning “collection of things bound together.”
According to an article in Archdaily.com, timber trusses were likely used as early as the Bronze Age, around 2500 BCE. Since then, they were used by the Greeks in antiquity and for various purposes during the European Middle Ages; later, Andrea Palladio’s famous Four Books on Architecture even included plans for wooden trusses.
In the 1950’s, developments in construction technology improved the efficacy of the wooden truss even further. Today, timber trusses are still commonly used for a variety of functions such as roof trusses due to their strength, economic use of materials, versatility, and sustainability.
South Africa prefers timber roof trusses
Timber roof trusses are the most preferred material to use for trusses because of its role in environmental sustainability, according to Timber IQ; “The Department of Forest and Wood Science from the University of Stellenbosch has conducted a study that compares several roof truss systems (South African pine, hardwood and LGS) found in low and medium income house designs in South Africa using simplified Life Cycle Assessment approach.
The results showed that the two timber trusses had the overall lowest environmental impact of the truss and building industry in South Africa. It is a fact that residential roof truss construction in South Africa is the single biggest user of locally produced structural timber which is mostly South African Pine.”
7 Benefits of timber roof trusses
Timber roof trusses have many advantages:
It is flexible and versatile
Timber roof trusses can be linked to other trusses and components making them compatible with other structures. They can also create large open areas which enables designers and architects to get really creative. Partitions can also be moved without the building’s structural integrity being compromised.
It is Economical
Timber trusses are light in weight which makes it easier to install, there is no need for heavy machinery. The waste generated by timber at a building site is minimal, making clean-up work less costly. Timber trusses are also cost-effective because they are made from a sustainable resource.
It is Durable and Strong
Most of the on-site framing problems are eliminated with timber trusses. They can be expected to last as long as the home itself (100+ years), if they are maintained in a stable, reasonably dry environment. You can expect an even longer life span if the timber is CCA treated because it is protected against environmental elements, insects and decay.
It is Energy Efficient
Timber is known to have excellent thermal properties making them more energy efficient. Timber Trusses create cavities, which are easy to insulate and save space.
It’s eco-friendly
Timber exhales in Co2, grabs the carbon for itself and releases the Oxygen into the environment. Around fifty percent of Timber by weight is carbon stashed safely away. Compared to other buildings, timber consumes much lesser energy to process and minimize air and water pollution. Timber is the only renewable construction material and helps define sustainable development very strongly.
It stays consistent
Unlike other materials such as steel, timber doesn’t expand in hot temperatures.
Readily available
According to Reinhardt Nolte, procurement director of Foresta Timber Group, the biggest area of commercial saw-log plantations in South Africa is planted with pine species, which explains why it is widely used in construction, DIY and shop fitting.
What to consider when using timber as the basic material for your roof trusses
It is vital that a roof structure is built correctly and in accordance to the SABS (South African Bureau of standards) regulations to ensure that it is strong, durable and safe. There could be severe consequences if a roof structure is not installed correctly, it could cause unnecessary damage to your building not to mention the possibility of injury. Can you just image your roof caving in while you are still inside? Here are some important factors to take in consideration first;
Availability of suited timber – In South Africa, Pine is grown in plantations all over and is one of our most cost effective timbers available.
Exposure to weather – Untreatedtimber should not be used if the truss cannot be fully protected from the weather. CCA treated timber, however, is protected against natural elements; this is one of the reasons why it is recommended.
Roof form – Timber trusses are highly suitable for many common roof forms.
Fire rating – Lightweight timber trusses have low fire resistance due to their slender dimensions and cannot be used for buildings requiring a high fire rating.
Jointing system – For timber trusses, the most common jointing systems are nails and bolts.
Transport and on-site handling – Due to their light weight, timber trusses are particularly suitable for construction in remote areas and at sites without hoisting devices. Most timber trusses can be handled manually.
We have the timber you need for any roof trusses
At Sabie Poles, we strictly deal with SABS approved S5 Construction timber when it comes to building structures. Our S5 construction timber is kiln dried and treated with class H2 treatment.
We have S5 Construction timber available for retail treated and untreated. Roof trusses can be built with untreated timber, however, we do recommend using treated timber to ensure strength and durability in your structure. If you are considering building close to the coast, treated construction timber is mandatory.
For our price list please click on this link: Sabie Poles Quotes
