I-Joists - Timber Floor Joists and Engineered Beams
Engineered timber I-Joists by Crendon Timber Engineering provide a high-performance, cost-effective alternative to traditional solid timber joists for floor and roof construction.
Engineered timber joists for modern floor and roof construction
These structurally engineered timber joists are currently used in most new homes. Manufactured with a web sandwiched between top and bottom flanges, which is glued, pressed and heat-cured, the I-shape cross section allows them to carry heavier loads than a conventional timber joist of equivalent weight.
Crendon offers 245mm and 300mm deep I-Joists from stock, which are the most popular sizes for domestic floors. If you require 225mm deep, Crendon can design and supply these in Posi-Joist metal web joists.
For commercial floors and roofs, 350mm and 400mm deep Type D I-Joists are also available.
I-Joist performance and benefits
I-Joists are a cost-effective alternative to solid timber floor joists and flat or shallow pitch roof members, eliminating shrinkage, splitting and warping. They offer a range of practical and commercial benefits, helping to improve build quality, reduce on-site labour and enhance overall construction efficiency. As a timber engineered alternative to traditional solid timber joists, they provide a more reliable and consistent solution for modern floor and roof systems.
High tensile and compressive strength in the flanges carries bending loads, while the 9mm OSB web provides high shear strength to support loads through the depth of the section.
Complete structural packages
Crendon Timber Engineering offers fully integrated structural solutions, ensuring I-Joists work seamlessly with:
By coordinating design, manufacture and delivery, we help reduce delays, simplify site logistics and improve overall build efficiency.
Case Study
Premier Inn, Barry Island
We used I-Joists on the Premier Inn, Barry Island project.
By using our off-site manufactured I-Joists, we:
- significantly reduced on-site build time
- supported improved health and safety
- ensured installation was easier through lightweight design and easier handling
What are the benefits of using I-Joists?
I-Joists offer a range of practical and commercial benefits, helping to improve build quality, reduce on-site labour and enhance overall construction efficiency. As an engineered alternative to traditional solid timber joists, they provide a more reliable and consistent solution for modern floor and roof systems.
Cost-effective solution
I-Joists provide an efficient alternative to solid timber joists, reducing material waste and improving overall cost control on both floor and roof applications.
Dimensional stability
Unlike traditional timber, I-Joists resist shrinkage, splitting and warping, ensuring long-term structural reliability and reducing the risk of defects.
Lightweight and easy to handle
Their lightweight construction simplifies transport and installation, helping to reduce on-site labour requirements and improve productivity.
Consistent quality
Manufactured to precise tolerances, I-Joists deliver reliable, repeatable performance across all units, improving build consistency.
Longer span capability
Engineered strength allows I-Joists to span greater distances, reducing the need for intermediate supports and enabling more flexible layouts.
Improved service integration
The design of I-Joists allows easier routing of services within the floor zone, simplifying installation and reducing additional site work.
I-Joist Gallery
Explore our gallery to see examples of our timber I-Joist solutions in use across a range of projects.
I-Joist FAQs
Find answers to common questions about I-Joists, including sizing, applications and performance.
What sizes of I-Joists do you supply?
We stock 245mm and 300mm deep I-Joists, with larger 350mm and 400mm options available for commercial use.
Are I-Joists better than solid timber joists?
Yes, I-Joist offers improved stability, eliminating shrinkage, splitting and warping while providing consistent performance.
Can I-Joists be used for roofs as well as floors?
Yes, I-Joist are suitable for both floor systems and flat or shallow pitch roof structures.
What other I-joist applications are there?
I-joists are used across a wide range of applications, including residential floor structures, flat and shallow-pitch roofs, commercial flooring systems, as well as extensions and loft conversions where strength, stability and efficient installation are key requirements.
Do you provide design support?
Yes, Crendon offers full design and engineering support to ensure the correct specification for your project.
What brand of I-Joists do you supply?
We supply James Jones I-Joists, known for their quality and reliability.
Are I-Joists suitable for commercial projects
Yes, deeper I-Joists are designed to meet the demands of commercial floor and roof applications.
What’s the difference between an I-joist and a Posi-Joist metal web joist?
The main difference is in the web design. I-Joists have a solid web, while Posi-Joist metal web joists use an open steel web. This means Posi-Joists allow services to pass easily through the joist, whereas I-Joists may require pre-planned service routes or limited drilling in specific zones.
How far can an I-joist span?
The span of an I-Joist depends on factors such as joist depth, load requirements and floor design. Typically, I-Joists can achieve longer spans than traditional solid timber joists, making them suitable for open-plan layouts. For accurate span calculations, a project-specific design is required.
How much do I-joists cost?
The cost of I-Joists will vary depending on the size, span, specification and project requirements. Larger spans or higher loadings may require deeper joists, which can affect cost. For an accurate quotation tailored to your project, please contact our team.
Can services run through I-joists
Yes, services can run through I-Joists, but this typically requires pre-planned holes or designated zones within the web. Unlike Posi-Joist systems, drilling or cutting must be carried out in accordance with design guidelines to maintain structural performance.
Do I-joists comply with UK Building Regulations?
Yes, all Crendon Timber Engineering I-Joists are designed to meet relevant UK Building Regulations and structural standards. Full design support and calculations are provided to ensure compliance for your specific project.
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