Timber Trusses – a comprehensive guide

In this article, you will learn all about timber trusses – the types of trusses, the benefits of a truss, the cost of the project, and the right way to order timber trusses.

What is a Roof Truss?

Timber trusses are prefabricated constructions that symmetrically cover the building from one end to the other and are custom made for each project. Trusses are made of high-quality C24 timber interconnected with special steel plates (Gang-Nail), resulting in an extremely durable construction.

Trusses are built on centuries-old and proven geometry principles, which, combined with modern engineering, provide a flexible, practical roof structure or floor solution that saves construction costs and installation time.

Truss specification

Roof trusses consist of timber planks where the connection points are arranged to form an interconnected triangular system that holds the load. These joints are connected with metal plates (6).

The Joints that carry the load on the supports are called the support joints. The timber that limits the truss from above forms the top chord (2), while the timber that is used for the tie beam is called a bottom chord (3).

Planks which are located between the upper and lower chords, forms a webbing. The highest point of the timber truss is called the apex or peak(4) and the continuation of the upper bar after the lower bar is called the overhang (5).

The distance between the load-bearing walls are called a span (1). The distance between the truss apex and the bottom chord is called truss height (7). Trusses allow you to save material compared to beams, which is used irrationally when using traditional rafters.

Truss types and design

Timber trusses are suitable not only for small garages and houses with a span of over 6 meters but also for large industrial objects with a span of up to 35 meters. Different types of wooden trusses and technical solutions provide practically unlimited possibilities of modelling roof structures and floor structures, which are developed and adapted to each project individually with the help of a specialised computer program. Some of the most popular types of trusses are:

• Triangular trusses are the most traditional form of trusses, which are widely used both for residential roofs and industrial buildings.
• Scissor-type trusses – used when it is necessary to raise the ceiling of the room.
• Attic trusses are most commonly used for the construction of the attic floor of private houses, or for the extension of single or multi-storey houses.
• Semicircular Trusses – Allows you to create various round roofs, extensions and domes.

Freimans Timber Constructions offers the following types of timber trusses:

Mansard timber truss allows the attic floor of the house to be created with higher ceiling height and wider living space.

Stubbed Modified timber trusses are used in the construction of both small and large objects, as this type of truss can be designed up to 35 meters without additional supports.

FLAT roof trusses can be used for roofing in timber structures or for roofing large projects (shopping centers, logistics parks or warehouses).

MONO timber trusses are mainly used for small objects such as garages, garden houses, small warehouses, since the optimal span of the MONO roof truss is up to 10 meters.

Stubbed MONO jumta kopnes izmanto pie palielinātām slodzēm.

ATTIC roof truss is highly popular within frame house manufacturers. With this timber truss, it is possible to obtain a large living space on the attic floor of the house.

Stubbed ATTIC timber truss solution is used at high loads on the attic floor.

DUO timber trusses are the most popular of all types of roof trusses available. The truss can be designed and manufactured up to 35 meters with no additional load-bearing walls in the middle.

Stubbed DUO with raised ends in support areas is used at higher loads because this design is able to withstand higher roofing and snow loads than DUO timber trusses.

Some myths about roof rafters

Rafters are a cheaper solution for roof construction. Rafters are considered by the public and often by professionals to be the most cost effective roofing solution, but this is a misconception. Roof rafters are a cost-effective solution only if you need to construct a smaller project, such as increasing your living space or adding a house extension.

Setting up rafters is quick and easy. this assumption is also misleading. Comparative studies show that the installation of roof rafters can take up to 2.5 times more than the installation of wooden trusses.

Using roof rafters requires less wood. This is probably one of the most common myths about roof rafters. On the contrary, installing roof rafters creates more wood waste. A comparative study found that it takes 30% more wood to install a rafting roof than using roof trusses.

Advantages of timber trusses

The main difference between timber trusses and traditional roof rafters lies in the preparation and installation aspects, but the main advantages of timber truss solution is the remarkably high installation speed compared to rafters. Also the timber trusses has lower costs than metal structures and at least 30% less timber waste than classic rafters structure. But these are not the only pluses of wooden trusses!

Size and shape. Timber trusses allow a production of large span structures that do not require additional load-bearing walls up to 35m. Roof trusses are made for each individual project, adapting the trusses to any type of shape. Trusses are very versatile and can be easily combined with other structures such as steel beams.

Manufacture. Structures are designed with the help of specific software, which enables fast, high-quality construction with millimetre precision and regional standards.

Variations. Thanks to the aforementioned design program, timber truss structure provides unlimited planning and re-planning possibilities.

Quality. The trusses are manufactured in-house and are not exposed to changing weather conditions, maintaining high quality standards.

Montage. Trusses delivered on site are ready for installation and do not require any special knowledge or highly qualified personnel. Usually the assembly for private house roof takes 1 to 2 days.

Ecology. Timber trusses are an eco-friendly product with a relatively simple production process that prevents unnecessary consumption of wood resources.

How timber truss price is calculated?

Of course, one of the most important factors that interest any future homeowner and builder is budget. There are several factors that influence the cost of timber trusses:

• Overhang
• Roof slope
• Truss step
• Truss count
• Roof loads
• Truss span

Information needed to create a timber truss offer:

• Address of the project
• Roofing
• The function of the building
• Desired truss assembly date
• Drawings – Section, floor plan, etc.

Why do we need to know the project address? Location is an important factor that will be used to determine the snow and wind loads that are different at each location. Therefore, it is important to know the exact location of the project in order to design trusses.

Why do we need to know what purpose will the building serve? Building functionality helps determine the necessary parameters and standards to guide the design of the trusses for the project, so it is important to know if the trusses are for the home, supermarket, pavilion, garage or other buildings.

Why do we need project drawings? This is probably the main factor influencing the cost of the project, since it is the drawings that show the structure of the building and the required distance between the trusses, which helps determine how many trusses will be needed to cover the roof. The standard distance between the trusses for metal roofing is 1.20m and for tile roofing – 0.9m. However, there are cases where the distance between the trusses is different. The more timber trusses needed for the project, the cheaper the cost of a single truss. Because whether we make 1 or 10 trusses, we still need to design, manufacture and deliver them, so from a cost point of view, more trusses are cheaper. This is also the reason why small roof extensions or small garages are more economical with other roof solutions.

How important is the choice of truss type? We have already mentioned that there are different types of trusses available. Type of the timber truss will influence the living space, ceiling height of the room and the cost of the project.

Why do we need to know your roofing material? The type of roofing determines the weight that the truss will need to support.

Example of truss costs calculation

Here is an example to give you a clearer idea of how project costs are calculated. Suppose a customer needs trusses for a private house with a roof area of 12.6m x 9m with a metal tile roofing.

1. Creating building geometry. In this step, the geometry of the building is created based on the parameters of the clients project.

2. Creation of the roof plane. Based on customer information and the project design analysis, our engineer determines the height of the roof and the slope of the roof.

3. Truss creation. Once the roof plane has been drawn, the trusses themselves must be created. Trusses are made based on several factors:

• Snow load.
• Wind load.
• Roof weight.
• Net weight.
• Weight of roofing.
• etc.

4. Truss placement in the roof plane. Based on the design parameters and the roof plane, the timber trusses are positioned to support the entire roof area.

5. Calculation of the offer. Because this project has a very simple solution, you only need to produce one truss variant, but sometimes there are projects that use more than 50 truss types. All in all, we see that this project requires the manufacture of 9 trusses, 2 rafters and the addition of mounting parts (optional). Total cost of the project with delivery and VAT is 1427,16 EUR.

Find out the price of timber trusses for your project. Order a timber truss price quote and truss plan here – Order a timber trusses

Things to know about ordering and installing trusses:

1. The time of timber truss manufacture and the project calculation depends on the complexity of the order and other factors, so the truss manufacture and design time can vary between a few days to several weeks. We recommend that you order the project creation immediately after you started groundworks.
2. Truss installation requires lifting crane to lift trusses to a certain height above the ground. Sometimes it is possible to mount trusses using a rope system, but using a crane will be much faster and easier.
3. The most attention and precision is required when lifting the truss. The precision of the first truss placement will determine how the rest of the installation process and quality will progress. Freimans Timber Constructions provides the customer with specific truss assembly scheme, which allows you to determine where and how each truss should be positioned.