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

What is a Posi-Joist?

Posi-Joists, also known as Metal Web Joists, are a structural system combining timber and steel webbing, designed for use in both floor and roof applications. Each joist consists of a top and bottom chord, end columns, and steel webs positioned in between. Unlike traditional joists, they're designed in specialist software and made in a controlled environment, allowing us to add or subtract loads, try different variants, or position them in various ways before the manufacturing process begins.

Why do they exist?

The demand for Posi-Joists has grown primarily due to two factors: the need to span greater distances, particularly in open-plan homes, and the ability to accommodate modern services like MVHR (Mechanical Ventilation with Heat Recovery) systems, which can pass through the joists without requiring modification.

Think back to the bygone era of homes with drawing rooms, pantries, cellars, a multitude of hallways and, in essence, more segmentation than we have now. All of these rooms were separated with brick walls that were thick enough to defend castles and strong enough to support a small mountain. The first floor joists were happily supported by these walls and there was no need to innovate anything better. Fast forward a little while and someone decided they didn't want rooms anymore unless it was for sleeping or dropping the proverbial kids off at the pool. Traditional joists couldn't quite cut it, so some clever engineer came up with what we now know as the metal web joist, or Posi-Joist. These could span greater distances than a solid joist, weighed significantly less and, quite helpfully, had a bunch of gaps in. These gaps doubled-up as an easy way to route services such as plumbing, electric and ventilation, eliminating the need to drill a plethora of holes.

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What are the benefits?

  • Strength 💪

    Their main benefit lies in their inherent strength and stiffness. Thanks to the clever combination of timber and steel in their design, Posi-Joists can span greater distances than solid timber, reducing or even eliminating the need for load-bearing walls or steel beams. Posi-Joists are also available in a range of depths—you can specify these yourself or we can work out which will be most cost-effective for your project.

  • Service Routing 🚽

    Thanks to their open-web structure, they can accommodate various services without modification. With solid joists, an installer would have to drill, cut and hack away material, potentially limiting their strength and performance. Posi-Joists allow, in theory, an infinite amount of paraphernalia to be installed through the joists.

  • Weight 🏋️‍♂️

    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.

  • Ease of installation 🔨

    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.

  • 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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FAQs

What are the benefits of using Posi-Joists?

They offer increased strength, reduced weight and greater spanning capabilities, allowing for more open floor plans.

How do Posi-Joists differ from traditional joists?

Posi-Joists have a unique web design that accommodates services like plumbing and electrical wiring without the need for drilling.

How far can Posi-Joists span?

The span can vary, but Posi-Joists are designed to accommodate longer spans than traditional joists, usually between 4 and 10 meters.

How much do Posi-Joists cost?

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