C&W Berry supply Engineered Timber JJI I-Joists as complete systems, offering a high-performance alternative to traditional structural timber beams. With longer lengths, straight and uniform dimensions, and a composition that resists shrinking and warping, these joists provide a reliable and sustainable solution for modern construction projects. Lightweight yet strong, JJI-Joists are ideal for a wide range of applications, including floor joists, rafters, purlins, and wall studs, making them highly versatile for modern construction.
This page provides a comprehensive guide to understanding JJI-Joists, covering everything from their technical specifications and dimensional options to their availability from C&W Berry. You’ll find detailed information on depths, flange widths, lengths, and load capacities to Eurocode 5 detailed on a downloadable PDF.
You can also use this page to send an enquiry directly to C&W Berry, whether you need expert advice on choosing the correct joist, require a quotation for a specific order, or have questions about lead times or availability. Our team is ready to provide tailored guidance to help with your building project.
Information About the Manufacturer
James Jones & Sons Ltd has been a family-run leader in the timber industry for over 180 years, combining tradition with innovation. From supplying timber for historic expeditions to developing advanced timber engineering solutions, the company operates Europe’s most technologically advanced sawmilling facilities. Today, James Jones is at the forefront of UK I-Joist manufacturing, producing high-quality engineered timber products for modern construction.
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What is a JJI-Joist?
JJI-Joists are advanced engineered timber beams designed to offer superior performance and versatility compared to traditional solid timber. Manufactured from high-grade, finger-jointed softwood flanges combined with a 9mm thick Oriented Strand Board (OSB) web, these joists deliver a remarkable strength-to-weight ratio while remaining straight, uniform, and stable. Their engineered composition resists shrinking, warping, and twisting, making them highly reliable for modern construction projects. Available in depths of 220mm and 245mm, lengths of 10 and 12 metres, and flange widths of 47mm, 63mm, 72mm, and 97mm from C&W Berry, JJI-Joists are precision-engineered to UK preferred dimensions, enabling designers and builders to optimise structural performance while maintaining consistent quality. Accredited to PAS 2050, they also provide a sustainable building solution.
Beyond their structural reliability, JJI-Joists offer practical benefits that improve efficiency on site. Their lightweight construction and uniform dimensions reduce transport costs and simplify handling during installation, making them ideal for floor joists, rafters, purlins, and wall studs. James Jones’ Forrest plant produces the UK’s largest standard range of JJI-Joists, with over one million linear metres in stock, ensuring reliable lead times. Precision manufacturing minimises waste and supports cost-effective construction, while the engineered design allows longer spans and higher load-bearing capacity compared to traditional solid timber. This combination of strength, stability, and sustainability makes JJI-Joists a preferred choice for modern construction projects.
Understanding JJI-Joists
JJI-Joists are engineered timber I-beams, designed to deliver strength, stability, and efficiency in modern construction. Their performance is determined by a combination of dimensions, grades, and availability codes, which together dictate how the joist will behave in a building. The section below explores these factors in more detail.
1. Depth, Length, & Flange Width
Depth - The vertical height of the joist. Greater depth generally allows for longer spans and higher load-bearing capacity
Length - The standard lengths (10 & 12 metres) suit different floor or roof layouts. Longer joists reduce the number of supports needed
Flange Width - Engineered to provide the necessary bending and shear capacity. Wider flanges correspond to higher grades (D > C > B+ > A+)
2. Performance Grades & Internal Strength
| Grade | Flange Width | Description |
|---|---|---|
| A+ | 47 mm | Lowest bending and shear capacity; suitable for shorter spans and lighter loads |
| B+ | 63 mm | Moderate capacity; suitable for typical domestic projects and moderate spans |
| C | 72 mm | Medium-high capacity; suitable for standard residential and light commercial projects |
| D | 97 mm | Highest bending, shear, and stiffness capacities; suitable for long spans and heavy loads |
3. Reading the Codes
Each JJI-Joist has a code that communicates its specifications. For example, 220mm I-Joist 10 Metres A+ denotes the following:
Higher-grade joists (D > C > B+ > A+) are engineered to carry greater loads and span longer distances without additional support.
At C&W Berry, we help you select the right depth, length, flange width, and performance grade to complete your JJI-Joist system. Choosing the right joist system for your construction project requires a clear understanding of the dimensions, grades, coding and hanger support. For more detailed technical specifications and installation guidance, click the PDF button below or contact us using the form below.
Technical SpecificationJJI-Joist Availability
C&W Berry supply JJI-Joists as complete systems only. Individual joists are not available for sale. Please refer to the table below for the available depths, lengths, and grades. To make an enquiry, please utilise the contact form below.
| Depth | Length | Grade |
|---|---|---|
| 220 mm | 10 metres | A+ |
| 220 mm | 12 metres | A+ |
| 220 mm | 10 metres | B+ |
| 220 mm | 12 metres | B+ |
| 220 mm | 12 metres | C |
| 220 mm | 10 metres | D |
| 220 mm | 12 metres | D |
| 245 mm | 10 metres | A+ |
| 245 mm | 12 metres | A+ |
| 245 mm | 10 metres | B+ |
| 245 mm | 12 metres | B+ |
| 245 mm | 10 metres | C |
| 245 mm | 12 metres | C |
| 245 mm | 10 metres | D |
| 245 mm | 12 metres | D |
Make an Enquiry
To make an enquiry for a complete JJI-Joist system, please utilise the form below - providing as much information as possible. Please note, individual JJI-Joists are not available for sale.