We are an authorised distributor of James Jones & Sons timber i-joists.

The JJI Joist is a structural, engineered timber i-joist, manufactured to UK preferred dimensions. Ideally suited for both residential and commercial applications, JJI Joists are available in a range of sizes (see our product comparison chart below for more information) and are FSCĀ® and PAS 2050 accredited.

Product features and specifications

Superior strength

With a high strength to weight ratio, i-joists can be supplied in longer lengths than solid timber.

Quicker to install

I-joists weigh much less than solid timber joists, so are easier and faster to install.

High structural efficiency

I-joists don’t bow, warp or split, so your building will be stronger.

David Smith St Ives - I-joists for Sarek Roundhouse project

Durability and treatment

 

Standard product

JJI-Joists are untreated and when used in a Service Class 1 or 2 environment, the European Technical Assessment (ETA) certificate advises that the joists can be expected to have a service life in excess of 50 years.

Preservative treatment

JJI-Joists are also available with preservative treated timber flanges. This allows their use in Use Class 2 conditions in accordance with BS EN335-1, and Hazard Class 2 conditions in accordance with NHBC. This treatment does not affect the structural properties of the JJI-Joist. Please note a minimum order quantity will apply.

 
Tell us about your project

Compare joist depths and sizes

Joist depthA+B+CD
47mm63mm72mm97mm
195mm
220mm
235mm
245mm
300mm
350mm
400mm
450mm

Download the Site Construction and Hole Guide

View the Interactive Span Table

Speak to an expert

Adam Ding

Our account is managed superbly. David Smith St Ives is a fantastic company to work with.

Jason Tooke, Materials Manager, Croudace Homes

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