In modern construction, trusses are an essential element for creating stable, durable, and efficient structures. A truss is a structural framework made of triangular units to support heavy loads over large spans. The in-built stability and strength of triangular combinations make them ideal for supporting roofs, bridges and other architectural structures. This article will explore the different types of trusses, like wooden trusses and steel trusses, and their advantages, properties, and role in construction, especially in truss roof design and truss building.
Key Properties of Trusses
- Load distribution: Trusses are good at distributing loads across their triangular framework, reducing the risk of localized failure. This makes them ideal for supporting heavy roofs and long-span bridges.
- Lightweight: Though powerful, trusses are lightweight compared to other structural systems, particularly in the case of wooden trusses used in residential construction.
- Durability: Steel roof trusses and metal roof trusses are known for their longevity and resistance to environmental factors like corrosion, fire and pests.
- Rigidity: Trusses provide a high degree of rigidity, preventing excessive movement or deformation under load.
- Scalability: From small, trussed roofs in homes to expansive steel-framed industrial buildings, trusses are scalable and adaptable to a wide range of construction needs.
Materials Used in Trusses
Trusses are made from either wood or metal, with wooden trusses and steel trusses being the most used materials in construction.
- Wooden Trusses
Wooden trusses are preferred for residential and light commercial buildings due to their cost-effectiveness, ease of construction and aesthetic appeal. Wooden roof trusses can be premade and installed quickly, making them suitable for smaller buildings. However, wood is susceptible to moisture, rot, and pests, so proper treatment is necessary to ensure long-term durability.
- Steel Trusses
Steel trusses are normally used in large-scale industrial buildings, bridges, and structures where strength and durability are essential. Steel roof trusses and steel frame trusses are highly resistant to environmental factors like corrosion, making them suitable for heavy-duty applications. They can span much longer distances than wooden trusses and are more fire-resistant.
- Metal Roof Trusses
Trusses can also be made with other metals such as Aluminium, to be used for structures that need high strength-to-weight ratios. These trusses are perfect for large buildings with long spans, where minimal support columns are desired.
7 Types of Trusses in Construction
Many types of trusses are used in construction, each suited for specific applications based on factors like load-bearing capacity, span and material choice. Trusses are made from various materials, including wooden trusses and metal trusses like steel trusses, and they serve specific purposes based on the requirements of the structure. The brief about these trusses, as well as their application and benefits, are explained below.
1. King Post Truss
The king post truss is a traditional truss and the simplest type of wooden roof truss. It consists of a central vertical post (the king post) supporting the apex, two diagonal members and a horizontal tie beam. This truss is suitable for short spans, usually under 8 meters and is used in trussed roofs in residential structures.
| Applications | Benefits |
| Small residential buildings | Simple and economical |
| Short-span wooden roof trusses | Easy to construct and install |
2. Queen Post Truss
The queen post truss is similar to the king post but includes two vertical posts, allowing it to span longer distances between 8 to 12 meters. The design is often found in steel trusses and wooden trusses for medium-span buildings, supporting larger roofs with extra support in the middle of the span.
| Applications | Benefits |
| Medium-sized roofs | Greater span capacity than King post |
| Steel frame trusses in light commercial buildings | It provides increased stability and support |
3. Pratt Truss
The Pratt truss is widely used in steel roof trusses and wooden roof trusses. Its diagonal members face inwards, and the vertical member takes the tension forces, making it suitable for longer spans and heavy loads. This type of truss is found in industrial buildings and bridges, where load-bearing efficiency is important.
| Applications | Benefits |
| Bridges and large buildings | Efficient load distribution |
| Steel frames and trusses for industrial purposes | Suitable for long spans and heavy loads |
4. Howe Truss
In comparison to the Pratt truss, the Howe truss has diagonal members that slope outwards, taking tension forces and the vertical members in compression. This design is especially effective for heavy loads and long spans. Howe trusses are often used in steel roof trusses for large industrial buildings and bridges.
| Applications | Benefits |
| Railway bridges | Excellent for supporting substantial loads |
| Heavy-load-bearing structures | Suitable for large spans |
5. Warren Truss
The Warren truss uses equilateral triangles to distribute loads evenly across its structure. Its simple, repetitive design is ideal for both metal roof trusses and wooden trusses, making it an adaptable choice in various construction projects.
| Applications | Benefits |
| Long-span roofs and bridges | Uniform load distribution |
| Truss roof design in large halls and factories | Efficient use of materials and simple construction process |
6. Fink Truss
The fink truss is a common choice for residential and light commercial buildings. Its web-like arrangement provides excellent support for moderate spans and is used in truss roof design for homes. Fink trusses can be made from either wooden roof trusses or steel frame trusses.
| Applications | Benefits |
| Residential roofing | Lightweight and efficient and ideal for mid-span roofs |
| Light commercial buildings | Easy to fabricate and install |
7. Bowstring Truss
The bowstring truss features a curved top chord that provides aesthetic appeal while also allowing for large, open space beneath. This type of truss is used in large structures like aircraft hangers and sports arenas.
| Applications | Benefits |
| Sports halls and gymnasiums | Suitable for wide, open spaces |
| Hangers and large warehouses | Strong, durable, and visually appealing |
Benefits of Trusses in Construction
- Cost-effectiveness: Wooden trusses and metal trusses offer cost savings compared to other support structures. The lightweight design reduces the need for excessive materials, translating into lower material and labour costs.
- Strength and Stability: Trusses are strong and allow for efficient load distribution. Steel trusses can bear heavy loads, making them suitable for large industrial and commercial buildings.
- Material Efficiency: The geometry of trusses allows efficient use of materials, ensuring smaller, lighter components that provide maximum structural integrity. This allows for faster construction time when using prefabricated components.
- Long Span Capability: Trusses are perfect for open spaces like warehouses, bridges, and big auditoriums because they can span large distances without the need for intermediate supports. This is especially true for steel frame trusses.
- Sustainability: Wooden trusses are a sustainable option as they can be obtained from renewable timber. Steel trusses require more energy in production, are recyclable and contribute to sustainable practices.
- Design Flexibility: Trusses offer great flexibility in terms of design, for both residential and large industrial buildings. The various types of trusses ensure that architects and engineers can choose the best configuration for their projects.
Conclusion
Trusses are vital in modern construction, offering a cost-effective, durable, and flexible solution for supporting roofs, bridges, and large open spaces. Whether using wooden trusses for residential roofing or steel trusses for industrial structures, their triangular geometry provides strength, stability, and efficiency. The various types of trusses allow for flexibility in design and application, ensuring that the trusses will continue to be a crucial element in construction projects of all places.