Our JJI-Joists offer several advantages over traditional structural timber beams, these include longer lengths, a composition that resists shrinking and warping, an excellent strength to weight ratio, straight and uniform dimensions and, uniquely, our JJI-Joists are FSC® and PAS 2050 accredited.

The JJI-Joists produced by James Jones at our Forres plant have the largest standard range available in the UK and are available in depths from 195mm up to 400mm deep with four flange sizes to facilitate a high degree of design optimisation enabling you to put the right product in the right place.

To read more about how our JJI-Joist system works and to access all the technical information required to specify and work with JJI-Joists please read our Technical Manual as a page turner by clicking here.

The full range of JJI-Joists is shown in the table below:

Other sizes are available, please contact your sales representative for further information.

Joist depthA+B+CD


Use our Interactive Span Table to quickly find out what size JJI-Joists you'll require for your project.

How To Buy

JJI-Joists are available through our network of UK distributors, for contact details of your nearest distributor visit our Distributor Map.

Our distributors can provide you with a full design and quotation service, along with information about delivery time scales. Quotations typically include all required structural timbers and associated metal work.

Alternatively, contact our Timber Systems Division team directly, individual contact details can be found in our Contacts section.

Main Tel:
01309 671 111
Email: jji-joists@jamesjones.co.uk

Fire Retardent (FR) Treatment

James Jones and Sons has been heavily involved in the Structural Timber Association's on-going project to develop fire design guidance and test methods aimed at mitigating the risk of fire during construction of timber frame buildings.

As part of this work we have performed fire tests with flame retardants from two manufacturers with positive results. Where there is no alternative it is possible for us to supply a non-standard FR treated joist that complies with the Structural Timber Association Limited FR build requirements.

Pricing and delivery times on application.

Durability and treatment

Standard product

JJI-Joists are untreated and when used in a Service Class 1 or 2 environment, the ETA certificate advises that they may be taken to have a service life in excess of 50 years.

Preservative treatment

JJI-Joists are 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.