JJI-Joists, the versatile choice.

JJI-Joists, from James Jones and Sons, are the market leading timber I-Joist in the UK. With over 60 million lineal metres produced to date, they are used by everyone from the volume housebuilders to self-builders looking for maximum thermal performance and minimum carbon footprint.

More and more architects and builders are recognising that using JJI-Joists to construct walls and roofs gives them the opportunity to maximise the insulation they are able to incorporate into a building. The shape of the JJI-Joist, with its 9mm OSB web means that cold bridging is reduced and the wide choice of joist depths make it easy to choose a specification that meets the specific design requirement to suit the building and location.

Both architects and builders are turning to JJI-Joists when looking to build to Passivhaus standards, using the joists in stick build construction or pre-fabricated cassettes. Because the JJI-Joist allows for high levels of insulation and is easy to work with onsite, creating a structure which meets Passivhaus standards for airtightness is more straightforward, aided by the OSB web which outperforms a metal web joist when it comes to controlling air movement.

JJI-Joists are supplied in a wide range of standard sizes, with joist depths from 195 to 450 and flange widths ranging from 47mm to 97mm. JJI-Joists can be specified in lengths up to 12 metres and are ideal where a longer span, lightweight roof is required, in school buildings for example. This means architects, engineers and building contractors know that they can easily specify the right joist for a job.

JJI-Joists come with the best design and engineering support in the business with a team of regional technical sales staff backed up by a 12 strong design and engineering resource at our manufacturing plant in Scotland.

With impeccable environmental credentials, including being available with FSC or PEFC certification, JJI-Joists are the only I-Beam on the market that can be supplied with independently verified carbon data, meaning that we can accurately tell you the carbon impact of the joists in your job.


The JJI-Joist system is designed to make your job easier, whether you are an architect, engineer or builder; choosing JJI-Joists means you are guaranteed total peace of mind.

For more information please visit www.jamesjones.co.uk/ewp