Shed Purlins

Ryedale Timber supplies high-quality timber purlins to builders and farmers across North and East Yorkshire. These horizontal structural members are essential for supporting roof loads, redistributing weight from the cladding or rafters to the primary building frame or gable walls. Our range includes standard C16 grades for general use and premium C24 grades for larger spans and heavy-duty agricultural specifications.

What are Timber Purlins?

In roof construction, a purlin is a longitudinal beam that runs parallel to the building’s ridge. Unlike common joists, purlins are designed to support the “imposed loads” of a roof—such as snow and wind—while managing the “self-weight” of the roofing materials themselves.

At Ryedale Timber, we specialise in long-length tanalised purlins, typically available in 15ft and 20ft spans, ensuring you can achieve the required coverage with minimal joints.

Structural Configurations & Support

The way purlins are integrated into your roof design significantly impacts structural integrity and the overall profile of the building:

Under-Purlins: Positioned beneath the rafters to reduce their effective span, allowing for thinner rafter sections.

Flush Purlins: Set at the same level as rafters using joist hangers, creating a streamlined roof profile often used in modern residential builds.

Through Purlins: Sit directly on top of principal rafters, a common choice for simplifying installation in large sheds.

Common Purlins: Closely spaced beams that support roof cladding directly, eliminating the need for secondary rafters entirely.

To ensure stability, we recommend using cleats (timber or steel blocks) to prevent sliding and knee braces to provide lateral stability and reduce the effective span.

Key Technical Design Parameters

When specifying timber purlins for your project, several variables must be considered to prevent lateral torsional buckling (twisting under load) or deflection (sagging):

Span: The distance between your primary supports (walls or trusses).

Spacing (Centres): Usually determined by the type of roof cladding being used.

Bearing Requirements: It is vital to ensure sufficient “bearing” at the ends (often on masonry corbels) to prevent crushing the timber fibres.

Timber Purlin Specifications

We stock a variety of sizes suited to different load requirements and spans.

Important Technical Warning: Do not substitute a specified C24 purlin with a C16 grade. While they may look identical, C24 timber is denser and has fewer knots, providing the higher bending strength required for long spans. Using an inferior grade can lead to shear failure or excessive sagging over time.

Why Choose Ryedale Timber for Structural Projects?

Yard-Managed Quality: We manage our own yard in Pickering to ensure all lengths are stored flat and true, preventing the bowing often found in generic merchant stock.

Pressure-Treated Protection: For agricultural and open-sided buildings, we recommend our tanalised (pressure-treated) purlins. This treatment is essential for protecting against rot and woodworm infestation in environments where moisture levels can fluctuate.

Direct Delivery: We operate our own fleet of vehicles, ensuring that the purlins arrive on-site safely and on schedule across North and East Yorkshire.

Timber Purlins: Local Expertise & Quality

Ryedale Timber is a specialist supplier of structural and agricultural timber. From our base in Pickering, we ensure every purlin meets the strict grading requirements for British construction.

We serve trade and DIY customers within 30 miles of Pickering, North Yorkshire. Our delivery teams provide reliable service to York, Scarborough, Malton, and Thirsk. We are also the preferred supplier for rural projects in Driffield, Bridlington, Whitby, and Filey.

For remote farm builds and coastal renovations, we regularly deliver to Helmsley, Kirkbymoorside, Easingwold, Pocklington, Guisborough, and Robin Hood’s Bay.

Timber Delivery: North Yorkshire & East Yorkshire

We deliver our full range of Timber Purlins to the following areas. Deliveries typically take 3–5 working days.

Related Timber Products

• C16 Structural Timber – for internal framing and studwork
• C24 Structural Timber – for maximum load-bearing performance
• Timber Cladding – ideal for finishing agricultural sheds
• Timber Fencing – for perimeter security and agricultural enclosures

Frequently Asked Questions

Are purlins and joists the same thing?

No. While both are horizontal structural beams, they serve different purposes. A joist typically supports a floor or ceiling and is supported by walls or larger beams. A purlin specifically supports the roof’s primary surface (cladding or rafters) and runs perpendicular to the roof’s slope, transferring the load to the building’s main frame or trusses.

What is the purpose of purlins?

The primary purpose of a purlin is to provide a support structure for the roof cladding (such as metal sheets or timber boarding) and to redistribute the roof’s weight to the rafters or load-bearing walls. They prevent the roof from sagging between supports and provide essential lateral bracing to the overall structure.

Can you replace a damaged purlin?

Yes, a damaged purlin can be replaced, but it is a significant structural task. Because purlins are load-bearing, the roof must be properly propped and supported before the damaged section is removed. We recommend consulting a structural engineer or professional joiner to ensure the “bearing” of the new purlin is sufficient and that connections like birdsmouth joints or cleats are correctly installed.

Are purlins load-bearing?

Absolutely. Purlins are critical load-bearing members. They must be calculated to withstand the combined weight of the roofing material, as well as environmental “imposed loads” such as heavy snowfall or wind pressure. Using under-sized purlins can lead to structural failure or permanent roof deformation.