Understanding the Different Types of Purlins Used in Construction
Structural support cannot be overemphasized in all construction works, especially those of industrial sheds or steel buildings. The purlin is among the unseen factors yet of most significant importance in roof system support.
Purlins are horizontal structural members and are the backbone of roofing systems because they support loads and strengthen the structure.
This article explains the various types of purlins employed in modern construction, their nature, application, and the selection method.
Whether building a warehouse, a metal shed, or a big commercial building, it is advisable to know the various purlins to make structurally sound and economically sound decisions.
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What are Purlins, and Why are they important?
Purlins are supported horizontal structural members or building frames or roof rafters. They bear roofing sheets and distribute their loads to the main structure. Purlins have a very significant function in:
- Offering mid-span support in roofing structures.
- Minimizing the spacing required between rafters.
- Enhancing durability and stability.
- The use of solar panels or mechanical loads in modern buildings.
Purlins, used mainly in pre-engineered buildings (PEBs) and steel frame structures, have developed specialized types to cater to load-bearing demands.
1. C Purlins
C purlins get their name from the cross-sectional shape, the letter “C” shape. They are commonly utilized as one of the most used forms of light and medium structures, as they are lightweight and easy to install.
Key Characteristics:
- It is light and easy to fix.
- In different thicknesses and depths.
- Strong to weight ratio.
Applications:
- Metal frame support for roof and wall framing.
- Use them as floor joists and girders.
- Ideal for the building of shorter spans.
Why use C Purlins? Their simplicity in design renders them highly versatile and suitable for horizontal and vertical uses, particularly in factories and small sheds.
2. Z Purlins
With their Z shape, Z purlins are employed in longer overlapping and span applications.
Key Characteristics:
- Their Z shape makes nesting by lap joints simple.
- They are more rigid than C purlins of equivalent material thickness.
- They are particularly well-suited for long flat rooflines.
Applications:
- Heavy roof span industrial shed.
- Pre-fabricated structures with longer roof spans.
- Most suitable where purlins overlapped for continuity.
Why Z Purlins? Overlap for longer than usual without loss of structure, less material, and quicker to install.
3. Box Purlins
Box purlins are made by face-to-face welding of two C purlins to create a closed box section. It imparts undue rigidity to the purlins in the buildings.
Key Features:
- Excellent resistance to torsion.
- Constructed to bear a considerable load.
- Stability over the larger roof space.
Applications:
- Heavy industrial roofings.
- Steel structures in windy climates.
- Big-span factories and sheds.
Why Use Box Purlins? Wherever extra support and strength are required without adding much weight to this support, box purlins provide it.
4. Sigma Purlins
The curved Sigma purlins offer extra strength and economy because of their shape, the name for which is derived from the Greek letter Σ (Sigma).
Key Features:
- Better structural performance as compared to the conventional C or Z shape.
- Of high tensile steel.
- Light and firm.
Applications:
- Large-span roofs need lighter framing members.
- Cheap industrial and commercial uses.
- In substitution of conventional purlins in the most modern steel structure.
Why Use Sigma Purlins? They promise better performance at reduced material usage and thus are economic yet efficient.
5. Eave Struts
Eave struts are a special purlin between the wall and roof joints to provide transverse or transitional support.
Key Features:
- L-shaped or irregular in most cases.
- Help in joining the wall and roof structures.
- Provide more edge support.
Applications:
- Pre-engineered structures.
- Roofs with projecting extensions.
- Transitional joints between the roof and the vertical wall.
Why Use Eave Struts? They provide for continuous structural modifications and are especially advantageous in buildings that have functional or aesthetic roof-wall intersections.
They are used most frequently in steel framing, especially for cold-formed purlins, because they work and last well. The positions of purlins in different steel arrangements are as follows:
- C purlins function best in roofs and short spans of walls.
- Z purlins provide the best performance in long spans and overlap functions.
- Box purlins provide maximum load-carrying capacity in heavy-duty applications.
- Sigma purlins possess the best strength-to-weight ratio in high-strength steel construction.
Purlins in Sheds: What's Best for You?
Materials’ affordability and the installation’s simplicity are factors for small buildings and sheds. These rough estimates are most typical:
- For small sheds and garages, use C purlins.
- For large and medium-sized sheds, use Z purlins.
- For farm sheds or machinery that should be built sturdy, use box purlins.
Choosing a proper purlin prevents future maintenance, enables longer roof life, and puts your shed’s load and weather at its optimum.
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How to Select the Right Purlin Type: The following are some points to note:
- Longer spans would require the supply of Z or Sigma purlins.
- Load Type: Heavy loads? Use box or Sigma purlins. C purlins are cost-effective for the majority of light structures.
- Corrosion Resistance: Pre-painted or galvanized steel purlins impart additional strength.
- Installation Requirements: Choose shapes that take minimal welding or bolting time.
Why Trust PISL for Your Structural Solutions?
At PISL, we don’t merely supply purlins; we provide total structural confidence. Our services include assisting you in selecting the correct profile, offering customized fabrication, and providing expert counsel. Our engineers make sure that every purlin is customized for your building needs.
Whether your requirement is for a steel warehouse, an agricultural shed, or a PEB installation, PISL brings advanced machinery together with turf experience to meet your unique needs. Our professional structural specialists in Gurugram undertake fast service, correct fit-up, and the highest reliability.
Conclusion on Types of Purlins
Purlins can look like a basic member; nonetheless, they play an essential role in the building. Proper choice can improve the distribution of loads, lower construction expenses, and extend the life of the roof structure.
Understanding many different shapes and types of purlins used in construction, such as C, Z, Sigma, and box shapes, will allow you to make the most informed decisions for your project’s specific needs.
From building a metal shed to a massive industrial complex, your building requires accuracy, precisely what PISL offers.
Frequently Asked Questions Regarding Types of Purlins
Q1. What are the types of purlins in construction?
The most common purlin shapes used in construction are C, Z, Box, Sigma purlins, and Eave struts. They are mainly applied to give structural support to walls and roofs in most building applications.
Q2. What are the types of purlins in steel structures?
Z, Sigma, and Box purlins are commonly found in steel structures as they possess a better load-bearing capacity, are light in weight, and can support longer spans.
Q3. What are shed purlins?
For sheds, C purlins are suitable for small structures, whereas Z or Box purlins are best for big sheds where strength and structural stability are needed.