a 3D render of a home with posi-joists installed

What is a Posi-Joist?

Posi-Joists, also known as metal web joists or engineered joists, are a structural system combining timber and steel webbing, designed for use in both floor joist and roof applications. Each joist consists of a top and bottom chord, end columns and steel webs positioned in between. Their benefits over traditional floor joists include their reduced weight, increased stiffness and ability to route services without drilling, notching or modifying in any way. Posi-Joists are designed in specialist software and manufactured using state-of-the-art machinery, ensuring millimetre perfect accuracy every time. Find out how far they'll span using our calculator here.

FAQs

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What are the benefits of using Posi-Joists?

Posi-Joists offer a number of benefits over solid joists or even other engineered joists. Posi-Joists provide an almost infinite number of service routing opportunities thanks to their open web design, leading to a reduction in labour costs and more flexibility when installing HVAC or MVHR systems. Along with this, they can span greater distances whilst weighing less than alternative options.

How do Posi-Joists differ from traditional floor joists?

Unlike a traditional solid floor joist, Posi-Joists feature metal webs connected to timber top and bottom chords, providing service gaps between the webs and reducing the overall weight.

How far can Posi-Joists span?

Posi-Joists can span up to around 10 metres, dependant on the amount of supports, the loads subjected to it, etc. For a rough example, you can use this span chart. For a more detailed answer, feel free to send us your plans for a custom design (free of charge).

How much do Posi-Joists cost?

Posi-Joists cost from around £25 ex VAT to over £200 ex VAT per joist.

How much do Posi-Joists weigh?

Posi-Joists available on our website weigh between approx 11kg and 48kg, although for bespoke designs they can be lighter or heavier. Click here for our Posi-Joist weight table.

What's included with a Posi-Joist online order?

When you order Posi-Joists from us, all strongback bracing timber is included, along with a comprehensive design that is send shortly after purchase. When the joists are delivered, you'll also receive laminated layouts to help with installation.

Are Posi-Joists treated?

The only treatment available for Posi-Joists is a pesticide that protects against the House Longhorn Beetle. It is only necessary if you live within the areas marked on this map.

Can you drill or notch Posi-Joists?

No—Posi-Joists, once designed and manufactured, generally can't be modified (with the exception of a trimmable end which is designed to be cut down by up to 130mm). If you need to modify a Posi-Joist we have already supplied, please contact us and we'll try our best to help.

Build a Posi-Joist Quote Online

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Why Choose Posi-Joists?

  • Long Spanning 📏

    Posi-Joists can span significantly greater distances than traditional solid timber joists while also offering a lighter overall weight. This makes them particularly well-suited for modern construction methods, where open-plan layouts are increasingly popular. The extended span capabilities of these metal web joists reduces or eliminates the need for internal loadbearing walls or intermediate supports, creating more flexible and adaptable floor layouts.

  • Easy Service Routing 🚽

    Thanks to their open web design, Posi-Joists also provide a convenient service void for running plumbing, electrics, and ventilation systems without the need for costly drilling or notching — reducing installation time and minimising potential structural compromise. Whether you're building a new home or undertaking a renovation, Posi-Joists offer a high-performance, cost-effective solution for almost every project.

  • Lightweight 🏋️‍♂️

    Posi-Joists use less material to achieve the same strength as solid timber, making them significantly lighter. This is a major advantage if you're working on a site that can't accommodate a crane or if you want to avoid the associated costs.

  • Easy to install 🔨

    Posi-Joists are manufactured to the size of your building and can be simply dropped into place. If your building isn't perfectly straight (which, let's be honest, most old buildings aren't), Posi-Joists can be supplied with trimmable ends.

  • High quality ✏️

    Posi-Joists are designed in specialist software and produced under factory-controlled conditions, ensuring an unmatched level of quality every time.

  • No shrinkage 🏡

    Posi-Joists don't suffer from shrinkage or distortion, a typical cause for a squeaky floor. 

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Why You Should Choose Posi-Joists

Thanks to upcoming regulations, Posi-Joists will soon be invaluable in the building of new homes and businesses. Not only will they save you time and money, but will future-proof your investment.

Posi-Joist Downloads

  • The World of Posi Technology

    This comprehensive guide to all things Posi includes standard details for masonry and timber frame construction, installation guidance, information on acoustic and fire performance and much more.

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  • Posi-Joist Brochure

    This brochure provides a general overview of the product outlining the many advantages of specifying Posi-Joist.

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  • Posi-Joist Acoustic Test Report

    Full acoustic test report for different Posi-Joist floor makeups detailing Posi-Joist’s different acoustic performances in different situations.

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