A Guide to Types of Timber Roof Trusses

Timber roof trusses are a crucial part of any building's structure, providing support and stability to the roof. They come in various types, each with its own unique characteristics and advantages.

The most common type of timber roof truss is the King Post truss, which features a single vertical post that runs from the base to the ridge. This truss is simple and cost-effective, making it a popular choice for many builders.

A King Post truss is ideal for small to medium-sized buildings, such as homes and garages. It can also be used in conjunction with other truss types to create a more complex roof design.

Pratt trusses, on the other hand, are more complex and feature a series of parallel chords that provide added strength and stability. They are often used in larger buildings, such as commercial offices and warehouses.

Our standard heavy timber roof trusses include four main styles: the King Post, Hammerbeam, Scissor, and Queen Post timber truss.

The King Post and Queen Post trusses are two of the most common types, often used in traditional and historic buildings. They're a great choice for homes with a classic look.

We also offer Hammerbeam trusses, which are typically used in larger structures, such as barns and warehouses. Their unique design provides extra support and stability.

Scissor trusses, on the other hand, offer a more modern aesthetic, often used in contemporary homes and commercial buildings. They're a versatile option that can fit various architectural styles.

For many projects, we design and fabricate custom trusses to fit individual structural and aesthetic needs.

Closed trusses are a type of timber roof truss that allows for a vaulted ceiling area. This is achieved through the use of interrupted tie beams or scissor trusses.

A closed truss can also be described as a roof framing that is open to view, not hidden by a ceiling. This design offers a unique aesthetic appeal and can be a great feature in certain types of buildings.

There are two main characteristics of closed trusses: they have an interrupted tie beam or scissor truss, and the roof framing is open to view.

The open trusses offer a more open look to the interior of the roof. This is achieved by using arch-braced trusses, which lack a tie beam.

A collar beam supported by a pair of arch braces stiffens the structure and helps to transmit the weight of the roof down through the principal rafters to the supporting wall.

The arch-braced truss has a more open appearance due to its design, which sets it apart from other types of trusses.

Pre-fabricated wood trusses offer advantages in building construction through machine-made accuracy and tend to use less timber.

Pre-fabricated wood trusses can be designed to meet specific building codes and regulations, which is a significant advantage in today's construction industry.

However, site-specific design alterations often require customized truss design, which can be a limitation of pre-fabricated wood trusses.

Our standard heavy timber roof trusses are designed to provide a solid foundation for your project. We offer four main styles: King Post, Hammerbeam, Scissor, and Queen Post timber truss.

The King Post timber truss is a classic style that's both functional and aesthetically pleasing. It's a simple yet effective design that's perfect for smaller projects.

The Hammerbeam timber truss is another popular option, known for its robust and sturdy construction. It's often used in larger projects where extra support is needed.

Scissor timber trusses are a great choice for projects with a lot of angles and curves. They're designed to provide maximum support and stability.

The Queen Post timber truss is a versatile option that can be used in a variety of applications. It's a popular choice for projects that require a balance of style and functionality.

Scissor trusses are a unique and stylish option for timber roof trusses. They offer a departure from traditional truss designs, with two beams running from the lower part of one rafter to the upper part of the opposite rafter.

These beams are notched and fitted together to create a smooth finish and strengthen the truss. The scissor truss style is ideal for steep roof pitches.

Scissor trusses can create a narrow, cottage-like aesthetic, perfect for those seeking something unique. They're also great for adding space for a peaked or "vaulted" interior ceiling.

Here are some key characteristics of scissor trusses:

Hammer Beam Trusses create dramatic vaulted spaces with a cathedral quality. They can be used to enhance the look of a building with embellishments.

The Hammer Beam Heavy Timber Truss is best for distributing the roof load. It includes posts that extend to the first floor system.

Wide, clear spans are required when using a Hammer Beam Heavy Timber Truss. Structural members would obstruct the view in such cases.

A Hammer Beam Truss is both dramatic and complex. It features an open-air center with a combination of heavy timbers, metal tie rods, and turnbuckles.

Modified Hammer Beam Trusses have a great look with their open design and arched webs and braces.

A king post truss typically consists of two principal rafters, a tie beam, and a central vertical king post. It's commonly used with two angled struts.

The king post is usually under tension, which requires sophisticated joints with the tie beam and principal rafters. This can be a bit tricky to execute.

In a king post truss, the king post is normally the central vertical element, while in a king bolt (rod) truss, it's replaced by a metal bolt (rod) of wrought iron.

The rafter truss is the simplest and most common type of roof truss, consisting of two rafters connected at the ridge, spaced about 70-100 cm apart. Each single rafter can have a maximum length of 6m.

Rafter Beams are a type of roof truss commonly used when the span of the external walls does not exceed 6-7 meters.

This type of truss consists of two rafters connected at the ridge and supported by a horizontal beam made of wooden flooring.

The beams can be directly supported on the wall or on the wall plate, with an interval spacing of 80-120 cm between each pair of rafters.

To ensure structural integrity, these rafters should not exceed 7 meters in length.

Rafter Beams are often used in conjunction with other roof truss components, such as purlins, to create a stable and secure roof structure.

In a well-designed Rafter Beam system, the horizontal beam provides additional support to the rafters, helping to distribute the weight of the roof evenly.

The simplicity and ease of installation of Rafter Beams make them a popular choice among builders and homeowners alike.

Bracing is a crucial aspect of roof trusses, and it's essential to understand its importance. Permanent bracing designs can improve the lateral stability of roof trusses, specifically with j chords.

Continuous lateral braces can prevent negative effects of lateral forces by being diagonally set in to brace the chord. The length of the chord determines the number of brace locations, which is a variable effect on the truss web.

A well-designed bracing system can make all the difference in a roof's stability. In purlin trusses, a horizontal element, called a purlin, is added to connect and brace the rafters. This helps distribute the pressure evenly and provides additional support.

The purlin is usually placed halfway up the length of the rafter, or slightly higher, to ensure stability. The recommended spacing between the rafters in this solution is 70-100 cm.

Purlin bracing is particularly useful in larger roof structures. For wall spans over 11 meters, a purlin-brace truss is a suitable option, providing even distribution of pressure and a rigid roof surface.

Struts can be added to trusses for a more elegant look, and embellishments such as radius cuts can be made for a unique appearance.

This design feature is particularly popular in the King Post Truss with struts, which is known for its bold appearance that can serve as a focal point of a home's design.

Adding struts to a truss can also increase its strength and stability, making it a great option for areas with high ceilings or open floor plans.

This type of truss design is very adaptable and can be used in a variety of spaces, including loft areas, great rooms, and entryways.

The King Post Truss with struts is also a cost-effective design option, making it a great choice for homeowners on a budget.

Early wooden truss connections were made with mortise-and-tenon joints, which were likely crafted at the construction site. These joints were prone to cracking due to shrinkage in unseasoned posts.

Holes were drilled slightly off-centre in older truss designs to allow the peg to pull the posts together with gravity. This anticipated structural behavior under loads.

Mortise-and-tenon joints were often located at the weakest point in the post, accelerating failure.

The use of mortise-and-tenon joints in early trusses was common, but they had their drawbacks.

A king post truss is a simple yet effective design that's commonly used in conjunction with two angled struts. It consists of two principal rafters, a tie beam, and a central vertical king post.

The king post is normally under tension, which requires quite sophisticated joints with the tie beam and principal rafters. This makes it a bit more challenging to build than other truss designs.

In a variation known as a king bolt (rod) truss, the king post is replaced by a metal bolt (rod), usually of wrought iron. This design is a great alternative when a traditional king post isn't feasible.

Roof trusses are the backbone of any building's structure, and the materials used to make them can make all the difference in terms of durability and cost.

Glulam is a type of engineered wood made from layers of wood pressed together with adhesives, offering exceptional strength and stability.

Glulam trusses are often used in heavy-duty construction projects due to their ability to withstand high loads and stresses.

The use of glulam trusses can also reduce the need for additional supports, such as columns and beams.

Oriented Strand Board (OSB) is another common material used in roof trusses, made from layers of wood strands pressed together with wax and resin.

OSB trusses are often less expensive than glulam trusses but may not offer the same level of strength and durability.

Steel trusses are also an option, made from hot-rolled steel sections that are bolted or welded together to form the truss shape.

Steel trusses are ideal for projects where high loads are expected, such as in commercial buildings or industrial facilities.

In some cases, a combination of materials is used to create hybrid roof trusses, offering the best of both worlds in terms of strength and cost.

The choice of material ultimately depends on the specific needs of the project, including budget, load requirements, and aesthetic considerations.