Trusses: Their types, benefits, and uses

Trusses are like the superheroes of construction. They are strong and sturdy structures made up of interconnected parts that help buildings and bridges stay stable and secure. 

Think of them as the backbone of these structures, providing support and distributing weight effectively. 

In this blog post, we will explore the basics of trusses in simple terms, understand what they’re made of, the different types you might come across, where they are used, and the benefits and potential drawbacks they bring. 

Basics of Trusses

Trusses are rigid structures composed of interconnected members designed to bear loads and distribute them efficiently. They consist of triangular elements, which give them exceptional strength and stability. 

The triangular shape prevents deformation and ensures that forces applied to the truss are transferred to the supporting members, such as columns or beams.

The triangular shape of trusses is crucial because it helps them stay strong and resist bending or twisting forces.

Components of trusses

Component	Description
Chords	The longest members of a truss. They form the main framework of the structure.
Web members	The diagonal members connect the chords. They transfer loads from the chords to the supports.
Joints	The points where the chords and web members meet. They allow the members to rotate freely.
Sag rods	Vertical members that prevent the chords from sagging under load.
Purlins	Horizontal members that support the roof sheathing.
Rafters	Inclined members that support the roof sheathing.
Ridge board	A horizontal member that runs along the top of the trusses and supports the ridge of the roof.

Materials Used in Truss Construction

Trusses are constructed using a wide range of materials, each offering unique properties and suitability for specific applications. 

Common materials include steel, wood, and aluminum. 

1. Steel trusses offer exceptional strength, durability, and versatility, making them suitable for large-scale industrial and commercial structures. 

2. Wood trusses, known for their affordability and flexibility, find extensive use in residential buildings. 

3. Aluminum trusses are lightweight and corrosion-resistant, making them popular in stage and event structures.

Truss Material	Advantages	Common Applications
Steel	Exceptional strength, durability, and versatility, High load-bearing capacity	Large-scale industrial structures, Commercial structures, Bridges, Warehouses
Wood	Affordability, Flexibility in design	Residential buildings, Timber-framed structures, Timber-framed structures, Small to medium spans
Aluminum	Lightweight, Corrosion resistance	Stage and event structures, Exhibitions and trade shows, Lighting and sound systems, Temporary structures

How are trusses made?

Trusses are made in factories using a variety of machines and tools. The first step is to cut the individual pieces of the truss to size. This is usually done using a CNC saw, which can cut the pieces to very precise dimensions.

Once the pieces are cut, they are assembled using metal plates or bolts. The plates or bolts are used to connect the pieces together at the joints. The joints are then reinforced with glue or another adhesive to make them stronger.

Once the truss is assembled, it is inspected to make sure that it is properly aligned and that all of the joints are secure. If the truss is approved, it is then packaged and shipped to the construction site.

Here are the steps on how trusses are made:

1. Design

The first step is to design the truss. This includes determining the size and shape of the truss, as well as the materials that will be used. The design is usually done by an engineer or a truss manufacturer.

2. Cutting

Once the design is complete, the individual pieces of the truss are cut to size. This is usually done using a CNC saw, which can cut the pieces to very precise dimensions.

3. Assembly

The pieces of the truss are then assembled using metal plates or bolts. The plates or bolts are used to connect the pieces together at the joints. The joints are then reinforced with glue or another adhesive to make them stronger.

4. Inspection

Once the truss is assembled, it is inspected to make sure that it is properly aligned and that all of the joints are secure. If the truss is approved, it is then packaged and shipped to the construction site.

Here are some of the machines and tools that are used to make trusses:

1. CNC saw
2. Metal plates
3. Bolts
4. Glue
5. Adhesive
6. Inspecting tools

Types of trusses

1. King Post Truss
2. Queen Post Truss
3. Howe Truss
4. Pratt Truss
5. Warren Truss
6. Fink Truss
7. Double Fink Truss
8. North Light Truss
9. Gambrel Truss
10. Lattice truss

1. King Post Truss

It is a type of roof truss that is made up of a central vertical post (the king post), two sloping rafters, and a horizontal tie beam. 

The king post is in tension, while the rafters and tie beam are in compression.

King post trusses are typically used for spans of up to 8 meters.

Advantages

1. Simple to construct
2. Relatively inexpensive
3. Strong and stable
4. Can be used for a variety of roof pitches

Disadvantages

1. Can be less efficient for attic space
2. Not as strong as some other types of trusses
3. Can be more difficult to transport

Where to Use

These are commonly used in residential construction and for smaller commercial and industrial buildings. They are a good choice for roofs that do not need a lot of attic space, and they can be used for a variety of roof pitches.

2. Queen Post Truss

A queen post truss is a type of roof truss that is similar to a king post truss, but it has two vertical posts instead of one. The queen posts are in tension, while the rafters and tie beams are in compression. 

Queen post trusses are typically used for spans of up to 12 meters.

Advantages

1. More efficient for attic space
2. Stronger than King post trusses
3. Easier to transport

Disadvantages

1. More complex to construct
2. More expensive
3. Not as versatile as king post trusses

Where to Use

Queen post trusses are commonly used in commercial and industrial buildings and for larger residential roofs. They are a good choice for roofs that need a lot of attic space, and they are stronger and more versatile than king post trusses.

3. Howe Truss

A Howe truss is a type of truss that is made up of a series of triangles, with diagonal members sloping down towards the center of the truss. 

The triangles provide the truss with strength and stability. The vertical members in a Howe truss are in compression, while the diagonal members are in tension.

Advantages

1. Less expensive to construct than Pratt trusses
2. Easier to transport than Pratt trusses
3. More efficient for attic space

Disadvantages

1. Not as strong as Pratt trusses
2. Not as versatile as Pratt trusses

Where to Use

Howe trusses are commonly used for bridges, as well as for roofs that need a lot of attic space. They are a good choice for applications where cost is a major factor, and where the strength of the truss is not the most important consideration.

4. Pratt Truss

It is a type of truss that is made up of a series of triangles, with diagonal members sloping up towards the center of the truss. 

The triangles provide the truss with strength and stability. The vertical members in this type of truss are in tension, while the diagonal members are in compression.

Advantages

1. Stronger than Howe trusses
2. More versatile than Howe trusses

Disadvantages

1. More expensive to construct than Howe trusses
2. More difficult to transport than Howe trusses

Where to Use

Pratt trusses are commonly used for roofs, as well as for other structures where strength is important. They are a good choice for applications where the cost of the truss is not the most important consideration, and where the strength of the truss is essential.

5. Warren Truss

This is a type of truss that is made up of a series of equilateral triangles. The triangles provide the truss with strength and stability. The vertical members in a Warren truss are in compression, while the diagonal members are in tension.

Advantages

1. Efficient use of materials
2. Lightweight
3. Easy to construct

Disadvantages

1. Not as strong as some other types of trusses
2. Not as versatile as some other types of trusses

Where to Use

These are commonly used for roofs and other structures where efficiency and lightweight are important. They are a good choice for applications where the strength of the truss is not the most important consideration.

6. Fink Truss

A Fink truss is a type of truss that is similar to a Warren truss, but it has a V-shaped pattern of diagonal members. 

The V-shaped pattern makes the Fink truss stronger than a Warren truss, but it also makes it more difficult to construct.

Advantages

1. Stronger than Warren trusses
2. More versatile than Warren trusses

Disadvantages

1. More difficult to construct
2. Not as efficient a use of materials as Warren trusses

Where to Use

These are commonly used for roofs, as well as for other structures where strength is important. 

They are a good choice for applications where the cost of the truss is not the most important consideration, and where the strength of the truss is essential.

7. Double Fink Truss

A double Fink truss is a type of truss that is made up of two Fink trusses that are placed back-to-back. This makes the double Fink truss stronger than a single Fink truss, and it also allows for a wider span.

Advantages

1. Stronger than single Fink trusses
2. Can span wider distances

Disadvantages

1. More expensive to construct than single Fink trusses
2. More challenging to construct than single Fink trusses

Where to Use

Double Fink trusses are commonly used for roofs and other structures where strength and a wide span are important. 

They are a good choice for applications where the cost of the truss is not the most important consideration, and where the strength and the wide span of the truss are essential.

8. North Light Truss

It is a type of truss that is used in industrial buildings. It is designed to allow natural light to enter the building through the roof. 

The North light truss is made up of a series of triangles, with the diagonal members sloping up towards the center of the truss. The triangles provide the truss with strength and stability.

Advantages

1. Allow natural light to enter the building
2. Strong and stable

Disadvantages

1. More expensive to construct than other types of trusses
2. More challenging to construct than other types of trusses

Where to Use

These are commonly used in industrial buildings, as well as for other structures where natural light is important. They are a good choice for applications where the cost of the truss is not the most important consideration, and where the natural light of the truss is essential.

9. Gambrel Truss

It is a type of roof truss that is characterized by its two-sloped roof. The upper slope is steeper than the lower slope, giving the roof a distinctive shape. Gambrel trusses are often used in barns and other agricultural buildings. 

Advantages

1. More efficient use of materials than gable roofs
2. Can span wider distances than gable roofs
3. Provides more headroom in the attic

Disadvantages

1. More expensive to construct than gable roofs
2. More challenging to construct than gable roofs

Where to Use

These are commonly used in barns, as well as for other agricultural buildings. They are a good choice for applications where the cost of the truss is not the most important consideration, and where the efficiency and the headroom of the truss are essential.

10. Lattice Truss

A lattice truss is a type of truss that is made up of a series of diagonal members that are arranged in a lattice pattern. The lattice pattern provides the truss with its strength and stability. 

Lattice trusses are often used in bridges and other structures where strength is important. 

Advantages

1. Very strong and stable
2. Can span wide distances

Disadvantages

1. More expensive to construct than other types of trusses
2. More challenging to construct than other types of trusses

Where to Use

These are commonly used in bridges, as well as for other structures where strength is important. 

They are a good choice for applications where the cost of the truss is not the most important consideration, and where the strength of the truss is essential.

Span ranges of different types of trusses

Truss Type	Span Range (m)
King Post Truss	5-8
Queen Post Truss	6-12
Howe Truss	12-25
Pratt Truss	15-30
Warren Truss	15-35
Fink Truss	15-30
Double Fink Truss	25-45
North Light Truss	15-30
Gambrel Truss	15-30
Lattice Truss	15-30

Spacing of Trusses

The spacing of trusses is determined by a number of factors, including the span of the roof, the type of truss, and the load conditions. 

In general, the economical spacing of trusses should be between 6 and 10 meters.

• For spans of up to 15 meters, the spacing of roof trusses can be kept 1/4 of the span.
• For spans of 15-30 meters, the spacing of roof trusses can be kept 1/5 of the span.

For example, 

if you have a roof span of 10 meters, the spacing of the roof trusses should be 10 / 4 = 2.5 meters. 

If you have a roof span of 20 meters, the spacing of the roof trusses should be 20 / 5 = 4 meters.

The reason for this rule of thumb is that the spacing of the roof trusses affects the strength of the roof. If the spacing is too wide, the roof may not be able to support the loads that it is designed to support. 

If the spacing is too narrow, the roof may be more prone to sagging.

The rule of thumb is just a general guideline. The specific spacing of roof trusses should be determined by a qualified engineer, who will consider the specific loads and conditions of the roof.

The type of truss also affects the spacing. For example, Howe trusses can be spaced more closely than Warren trusses.

The load conditions also affect the spacing. 

For example, 

if the roof is subject to heavy snow loads, the spacing of the trusses should be closer.

The following table summarizes the factors that affect the spacing of roof trusses:

Factor	Effect on spacing
Span of the roof	The wider the span, the wider the spacing
Type of truss	Some types of trusses can be spaced more closely than others
Load conditions	The heavier the loads, the closer the spacing

Uses of trusses

1. Roof Systems

It forms the framework for roofs in residential, commercial, and industrial buildings, providing structural support and stability.

2. Bridges

These are widely used in bridge construction, especially for longer spans, as they offer excellent load-bearing capacity and structural efficiency.

3. Industrial Structures

These are used in various industrial structures, such as warehouses, factories, and manufacturing plants, to support heavy equipment, machinery, and overhead crane systems.

4. Stage and Event Structures

These are extensively (widely) used in the entertainment industry for stage setups, lighting rigs, sound systems, and other event structures due to their strength, versatility, and ease of assembly.

5. Transmission Towers

These are also used in the construction of transmission towers to support overhead power lines and ensure their stability over long distances.

6. Sports Arenas and Stadiums

It plays an important role in the construction of large sports facilities, providing support for expansive roofs and accommodating wide spans without the need for obstructive columns.

7. Exhibition Halls and Convention Centers

These are commonly used in exhibition halls and convention centers to create large, open spaces, allowing for flexible floor plans and unobstructed views.

8. Aircraft Hangars

These are also used in the construction of aircraft hangars to provide clear-span structures, accommodating the storage and maintenance of aircraft.

9. Agricultural Buildings

These are used in the construction of agricultural buildings such as barns and livestock shelters, providing structural support for roofs and open spans for storage and animal housing.

10. Gymnasiums and Sports Facilities

These are used in the construction of gymnasiums and sports facilities to create wide and open spaces without the interference of columns, allowing for versatile use of the area.

11. Exhibition Booths and Trade Shows

These are commonly employed in the construction of exhibition booths and trade show displays, providing a lightweight and modular solution for creating attractive and customizable structures.

12. Residential Construction

It has extensive use in residential construction, especially in roof framing, providing structural support and allowing for flexible architectural designs.

13. Greenhouses

These are used in the construction of greenhouses to support the roof structure and facilitate the cultivation of plants and crops.

14. Theatrical Productions

These are used in theatrical productions for rigging and suspending stage equipment, lighting fixtures, and scenery elements, enabling dynamic and visually appealing performances.

15. Temporary Structures

These are commonly used in the construction of temporary structures for events, exhibitions, and festivals due to their ease of assembly, modularity, and portability.

Benefits of Using Trusses

1. Structural Efficiency (Strength)

These are designed to efficiently distribute and bear loads, maximizing their load-carrying capacity. 

Their triangular configuration allows for optimal weight distribution, reducing the need for excessive materials and supporting larger spans.

2. Versatility in Design

These can be customized to accommodate various architectural styles and design requirements. 

They can be engineered to create open and spacious interiors without the need for interior load-bearing walls or columns, providing flexibility in space planning.

3. Cost-Effectiveness

These are often prefabricated, allowing for faster and more efficient construction. Their lightweight nature requires less labor and equipment for installation. Additionally, their optimized use of materials helps reduce overall construction costs.

4. Speed of Construction

These are manufactured off-site, enabling precise fabrication and quality control. This leads to faster construction timelines as the pre-built trusses can be quickly assembled on-site, minimizing construction delays.

5. Durability and Strength

These are engineered to be structurally robust and can withstand heavy loads and forces. 

Depending on the material used, such as steel or engineered wood, it offers excellent strength, stability, and resistance to environmental factors such as moisture, pests, and decay.

6. Long Spans

These are capable of spanning long distances without the need for intermediate support, providing unobstructed interior spaces and design flexibility. 

This is especially advantageous in large-scale structures such as warehouses, arenas, and exhibition halls.

7. Energy Efficiency

It can be designed to accommodate insulation, ventilation, and other energy-saving features, contributing to the overall energy efficiency of the building. 

This helps in reducing energy consumption and lowering utility costs.

Disadvantages of trusses

1. Limited Interior Flexibility

The triangular design of trusses limits the flexibility for modifications and alterations to the interior space. Load-bearing walls or columns cannot easily be relocated or removed without careful consideration of the truss system.

2. Design Constraints

It may impose design constraints on the overall architectural layout and aesthetic options. The presence of truss members and connections can affect the appearance and restrict certain design elements.

3. Additional Engineering Required

Designing trusses requires specialized engineering knowledge and expertise. 

Structural engineers need to analyze and calculate the load-bearing capacity, stress distribution, and connections of the truss system, adding to the complexity and cost of the project.

4. Transportation and Handling

Trusses, especially those designed for large spans or complex structures, can be challenging to transport and handle. Their size and weight may require specialized equipment, careful planning, and coordination during transportation and on-site installation.

5. Maintenance and Repairs

Accessing and maintaining trusses can be more challenging compared to traditional roof systems. Any necessary repairs or modifications to the truss system may require skilled labor and specialized equipment, increasing maintenance costs.

6. Cost of Customization

Customized trusses to fit specific design requirements can be more expensive compared to standard truss designs. 

The additional engineering, fabrication, and manufacturing costs associated with customization contribute to the overall project expenses.

FAQ

Also, read

• Difference between rafters and trusses