Understanding I-Beam Joists: Engineered Timber in Construction

In the world of construction, every detail counts. The choice of materials can significantly affect the integrity and longevity of a structure. A material that has gained increasing popularity in recent years is the I-Beam joist, a revolutionary engineered timber product that offers unique advantages and considerations for builders and architects alike.

What are I-Beam Joists

I-Beam joists, also known as I-joists or engineered timber joists, are structural components designed to provide strength and stability in flooring and roofing systems. They are crafted from high-grade timber, typically oriented strand board (OSB) or laminated veneer lumber (LVL), and are shaped like the letter "I" to maximise strength-to-weight ratio.

Applications and Maximum Span of I Beam Joists

These innovative joists find widespread use in residential, commercial, and industrial construction projects. Their versatility allows for various applications, including floor and roof framing, wall studs, and even in engineered timber beams. The maximum span for I-joists depends on factors such as the load they will bear and the specific brand and model. However, typical maximum spans range from 10 to 24 metres, making them suitable for a wide range of building designs. Our expert team of designers can assist with your project to ensure that your I Beam application is safe, meets regulations and is cost effective.

Sizes and Advantages

I-Beam joists come in various sizes to accommodate different load requirements and span lengths. Common sizes include depths ranging from 9.5 inches to 24 inches and widths ranging from 1.5 inches to 5.5 inches. The main advantage of I-joists lies in their strength and dimensional stability. Their engineered design ensures consistent performance, minimising warping, twisting, and shrinking compared to traditional solid timber joists. Additionally, their lightweight nature facilitates easier handling and faster installation, reducing labour costs and construction time.

Considerations and Disadvantages

While I-Beam joists offer numerous benefits, they also come with considerations and potential disadvantages. One drawback is their susceptibility to moisture damage, especially during construction phases when they are exposed to the elements. Proper sealing and moisture management techniques are essential to mitigate this risk. Additionally, I-joists may require additional blocking or bridging to prevent excessive deflection or vibration, especially in longer spans or high-load areas.

Cost Comparison and Span Capabilities

When it comes to cost, I-Beam joists may have a slightly higher upfront price compared to traditional timber joists. However, their long-term benefits, such as reduced maintenance, improved structural performance and faster installation often justify the initial investment. As for span capabilities without support, this depends on various factors including the type of load, spacing between joists, and the specific engineering specifications. In general, I-Beam joists can span greater distances compared to solid timber joists, with some models capable of spanning up to 30 feet or more without intermediate support. This makes I Joists a far more versatile and attractive option in today's modern construction environment.


I-Beam joists represent a significant advancement in modern construction, offering strength, stability, and versatility in a lightweight package. Their engineered design and consistent performance make them a preferred choice for builders seeking efficiency and reliability in their projects. However, careful consideration of moisture management, additional support requirements, and cost comparisons are crucial for successful integration into construction projects. With proper planning and implementation, I-Beam joists can contribute to the creation of durable, resilient structures that stand the test of time.

With their ability to span wider spaces, their simpler, faster installation and their low maintenance once installed the construction industry has increasingly opted for I Beam Joists as the soltion of choice for house builds and other construction projects. 

At Harlow Engineered Floors we are one of the country's most promient suppliers of I Joists to the UK market. With an end to end design, quote, fabrication & delivery solution that not only incorporates your complete I Beam supply but also your chopboard flooring, relevant joists hangers and adhesives too, Harlow offer the complete package solution for your engineered joist project.

If you would like to learn more about our I Joist services visit us HERE

Or to make an enquiry about your I Joist requirement get in touch with us HERE or call: 01509 274182