Metal Purlin Installation, Applications, and Cost Considerations

Purlin to roof connection

In Part 1, we introduced the basics of metal purlins, covering their types, sizes and important roles in steel structures.

Now, we will delve into the practical application and installation methods of metal purlins. Understanding how to install purlins properly and controlling the cost reasonably is the key to ensure the success of your construction project.

In this section, we will analyze the installation steps of purlins, specific application scenarios, and cost management strategies step by step to help you maximize the utility of purlins in actual projects.

Table of Contents

Purlin spans, spacing and laps

Purlin Span

Purlin span is the distance a purlin can span without support. This distance directly affects the selection and design of purlins.

Different span types are suitable for different building requirements and structural designs.

Single Purlin Span:Single purlin span is the span of a purlin between two supports. This span type is usually used for smaller building structures and is suitable for light load roof or wall applications.

Double Purlin Span: A double purlin span is a purlin spanning three pivot points with additional support at the center pivot point. This increases the purlin’s load carrying capacity and is suitable for moderately loaded building structures.

Continuous Purlin Span: The continuous purlin span involves purlins spanning multiple pivot points to form a continuous support structure. This design can significantly increase the load carrying capacity of purlins and is commonly used in buildings that require long column-free spaces, such as industrial plants or large warehouses.

Purlin spacing consideration

Purlin spacing refers to the distance between neighboring purlins. Reasonable spacing design is essential to ensure the stability and safety of the building structure.

The choice of spacing usually depends on the type of purlin, the loading requirements of the building, and the design of the roof or wall.

Excessive spacing may result in excessive bending stresses on the purlins, while too little spacing may increase the construction cost.

Purlin Lap

Purlin lap is the overlap of two sections of purlin between pivot points. The lap can improve the overall stiffness and strength of the purlin.

In design, the selection of lap length needs to consider the type of purlin, material strength and loading conditions.

Insufficient lap length may lead to stress concentration at the joint, thus affecting the safety of the structure. Therefore, ensuring a reasonable lap joint design is essential for the long term stability of the building structure.

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Precautions for purlin construction

Spacing

During purlin construction, it is very important to ensure that the spacing between purlins complies with the design specifications.

Reasonable spacing can ensure the stability and load bearing capacity of the structure.

If the spacing is too large, purlins may be subjected to excessive bending stress, leading to deformation or failure of the structure.

While too small spacing may increase the material and construction cost. Therefore, setting the purlin spacing in strict accordance with the design requirements is crucial to the safety of the building.

Overlap end

The overlap end of purlin refers to the overlap of two purlin sections between the support points.

During construction, ensuring that the length and position of the overlap end comply with the design specification can enhance the overall strength and stiffness of the purlin.

Insufficient length of the overlap end may lead to localized stress concentration, thus weakening the stability of the structure.

Meanwhile, ensuring that the joints of overlapped ends are flat and firm can prevent stress concentration and material damage.

Purlin Placement

Proper placement of purlins is a critical step in the construction process.

When placing purlins, their flatness and alignment should be ensured to avoid uneven stresses caused by installation errors.

In addition, it should be ensured that purlins are firmly connected to the supporting structure by using appropriate fasteners and connections.

Care should also be taken to avoid excessive bending or deformation during placement to maintain the purlin’s load carrying capacity and structural stability.

Steel Purlin Connection

Purlin Accessories and Design

Purlin Accessories

In the process of purlin installation, accessories play a vital role. Common purlin accessories include:

Connectors: used to fix the purlin to the main structure or other purlins. The selection and use of connectors should be determined according to the type of purlin and load requirements to ensure a firm and stable connection.

Fasteners: these usually include bolts, nuts and washers, which are used to tightly fix the purlin and the connectors together. The quality and installation method of fasteners directly affects the loading capacity and structural safety of purlins.

Supports: Supports are used to enhance the strength of purlins, especially in long span applications. They can reduce the bending and deformation of purlins and increase the stability of the overall structure.

Seals: The use of seals at the joints between purlins and roof or wall panels prevents water penetration and protects purlins and the interior of the building from water damage.

Proper selection and installation of these fittings can ensure the overall stability and durability of the purlin system.

Purlin Design

Purlin design is an important part of building structure design. The following key factors need to be considered during the design process:

Load Requirement: The design of purlin should firstly meet the load requirement of the building, including the self-weight of the roof or wall, wind load, snow load and so on. Different loading conditions will affect the size, shape and material selection of purlins.

Span and spacing: The design of span and spacing of purlin is directly related to its bearing capacity and stability. The design should be based on the specific needs of the building and the appropriate span and spacing should be selected to ensure that the purlin can withstand the required load without excessive bending or deformation.

Material selection: The material of purlin is usually cold-formed steel, but other materials can be selected according to the special needs. The choice of material should take into account the strength, durability, cost and other factors.

Anti-corrosion treatment: In purlin design, the need for anti-corrosion treatment should also be considered. Especially in wet or corrosive environments, the selection of suitable anti-corrosion treatments (such as galvanized or coated treatments) is very important to extend the service life of purlins.

Uses of Purlins

Load Distribution: Purlins play a key role in load distribution in building structures. By supporting the roof or walls, they evenly distribute the loads (including self-weight, wind loads, snow loads, etc.) carried by these parts of the building to the main structural frame of the building.

This load distribution helps prevent localized stress concentrations and ensures the stability and safety of the entire building structure.

Structural Support: Purlins are more than simple support members, they provide essential stability in the overall structure.

By supporting the roof or walls, purlins help maintain the shape and structural integrity of the building, preventing deformation or collapse due to external forces such as wind or earthquake.

Spanning Capacity: The design of a purlin directly affects its spanning capacity, i.e. the maximum distance it can span without intermediate support.

This spanning capacity is very important, especially in buildings that require large spaces, such as industrial plants or warehouses. Larger spans reduce the number of internal supports and increase the flexibility of available space.

Stiffness and Lateral Stability: The stiffness of a purlin determines how much it will deform when carrying loads, while lateral stability helps to resist lateral forces such as wind pressure or seismic forces.

High stiffness and good lateral stability enable purlins to provide continuous support to prevent lateral displacement or collapse of the structure, thus ensuring the safety of the building.

Fixing points for roofing materials: Purlins provides the necessary fixing points for roofing materials. Whether they are metal roofing panels, shingles, or other materials, they need to be secured to the purlins.

With proper fastening methods, purlins ensure that roofing materials remain secure in all weather conditions, preventing them from loosening or falling off, thus extending the life of the roof.

Transferring loads to the main frame: Purlins not only distribute and support loads, but also transfer these loads to the main frame of the building.

This feature reduces the load on the main frame, making the entire structure more stable and helping to extend the overall life of the building.

Integration With Roof Insulation And Services: Purlins are often integrated with roof insulation and other building services (e.g., plumbing, electrical wiring).

Through proper design and arrangement, purlins not only support these systems, but also protect them from the external environment, thus enhancing the functionality and comfort of the building.

Adjustment of roof slope: Purlins can be used to adjust and maintain the slope of the roof. A proper slope helps in effective drainage and prevents water from pooling on the roof.

This not only reduces the risk of leakage and structural damage but also improves the durability and longevity of the roof.

Advantages of steel purlin roof

Suitable For Different Structures: Steel purlin roofs are extremely flexible and can be adapted to various types of building structures. Whether it’s an industrial plant, commercial building, or agricultural facility, steel purlins can be customized and applied according to different design needs. They are compatible with a wide range of building materials, providing stable and reliable support.

Providing Roof Support: Steel purlins play a key supporting role in roof structures. They can effectively share the loads of the roof, including dead weight, wind loads snow loads, etc., thus ensuring the overall stability and safety of the roof. Due to the high strength of the steel, steel purlins can provide excellent support over large spans, reducing the number of internal support columns and optimizing the use of space.

Non-combustible: Steel itself is fire resistant, thus steel purlin has high fire resistance. Compared to wood purlins, steel purlins will not burn in a fire, helping to improve the overall fire resistance of a building. This property makes steel purlins the preferred choice for many commercial and industrial buildings.

Lightweight: Although steel is very strong, steel purlins are relatively lightweight. This lightweight characteristic not only helps to reduce the total weight of the building, but also reduces transportation and installation costs. Lightweight steel purlins are easier to handle during construction and the installation process is faster, thus saving time and labor.

Long Life: Steel purlins are widely used for their excellent durability and corrosion resistance. With proper surface treatment, such as galvanized or coated treatment, steel purlins can withstand harsh weather conditions and prevent rusting and deterioration. This makes the service life of steel purlins far longer than other materials, reducing the cost of long-term maintenance.

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Cost of metal purlin

Material Cost: One of the main costs of metal purlin comes from the material itself. Steel prices are subject to market fluctuations, especially the cost of cold-formed steel may vary in different regions and periods.

Choosing the right type and size of material can control costs while meeting structural needs.

For example, thicker steels are typically more expensive, but they offer higher load-bearing capacity and durability.

Manufacturing and Processing Costs: The cost of manufacturing and processing metal purlins is also a factor to consider.

The complexity of the cold-formed forming process, the precision of machining required, and the scale of mass production all affect the final cost.

Customized size or special shape purlins usually cost more than standard size purlins.

In addition, surface treatment processes, such as galvanizing or coating treatments, also add extra costs, but these treatments can significantly extend the service life of purlins and are a more cost-effective investment in the long run.

Transportation Costs: Transportation costs for metal purlins are also part of the overall cost.

Because purlins are usually long and in large quantities, special loading and protection measures are required for transportation.

The transportation distance, the weight of the purlin, and the mode of transportation all affect the cost.

Choosing a supplier closer to the construction site can effectively reduce the transportation cost as well as reduce the additional cost due to transportation damage.

Installation Costs: Labor and equipment costs for installing metal purlins are another important cost component.

Installation of purlins requires the operation of specialized technicians and may be more costly, especially on roofs with large spans or complex building structures.

The cost of fasteners, connectors, and other accessories used in the installation process should also be included in the total budget.

Proper design and construction planning can reduce installation time and thus labor costs.

Long-term maintenance costs: Although metal purlins are known for their durability and low maintenance requirements, long-term maintenance costs still need to be considered.

When used in corrosive environments, regular inspection and maintenance may be required to ensure the structural integrity of the purlin.

Choosing purlins with good anti-corrosion treatment, although the initial cost is slightly higher, can effectively reduce the maintenance cost at a later stage, thus lowering the overall cost of ownership.

Install metal purlins correctly to optimize costs and benefits!

In steel buildings, the proper installation of metal purlins is critical. Purlins not only support the roof and walls, but also ensure the stability and durability of the entire structure. Through rational installation methods, accurate matching of application scenarios, and effective cost management, you can significantly improve the overall quality and economic efficiency of your project. As an expert in steel structure design and fabrication, Xinguangzheng is working to provide efficient and reliable purlin solutions for every project.

FAQ

Metal purlins are used to support the roof or walls of a building to help distribute and transfer the loads to the main structural frame to ensure structural stability and safety.

Purlins are used to support the roof or wall of a building, and at the same time distribute and transfer the loads to prevent localized stress concentration and enhance the overall structural strength and stability.

Purlins are the key elements in a building structure, providing the necessary support to ensure that the roof and walls can withstand various loads and maintain structural integrity.

Yes, purlins are load bearing. They are responsible for supporting the loads on the roof or walls and distributing these loads evenly to the main structure to ensure the stability of the building.

Yes, purlins are structural members. They play a supporting and load distributing role in a building to ensure the structural safety and durability of the building.

Purlins are commonly used in steel buildings and they are essential members when it is necessary to support the roof or walls and distribute the loads.

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James-Xinguangzheng Blog Editor
Content Writer

James is a senior steel construction expert at Xinguangzheng, specializing in solutions for industrial and commercial projects. He has extensive project management and design experience and shares insights on sustainable building and steel structure innovations by writing articles.

About Xinguangzheng

Founded in 1997, Xinguangzheng Steel Structure Group has over 27 years of professional experience in the steel structure industry. We have completed more than 5,000 projects in more than 130 countries around the world and hold international certifications such as EN1090 (CE) and ISO9001. Whether it is a complex industrial building or a large commercial facility, Xinguangzheng is always able to provide high quality and reliable steel structure solutions for our customers.

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