Our JJI-Joist system combines the JJI-Joist products with custom sized glued laminated timber (glulam) and system specific metalwork to create a highly flexible offering, ideal for framing structural floors, roofs and walls.

Like all James Jones' products, the JJI-Joist production process has been independently audited to PAS 2050 standard meaning we are able to provide accurate carbon negative numbers for those customers looking to measure the carbon footprint of their project.


JJI-Joists are the most widely specified engineered wood product in the UK and are used in residential and commercial construction as load-bearing and non load-bearing members for floors, walls and roofs.


James Jones & Sons' Timber Systems Division is a leading supplier of high specification glued laminated timber (Glulam) specifically sized to suit the JJI-Joist product range, in partnership with Austria-based Binderholz.


​In partnership with Stora Enso, we supply the UK construction sector with laminated veneer lumber (LVL) suitable for a wide range of structural applications and in sizes to complement our JJI-Joist range.

Interactive Span Table

If you are considering using JJI-Joists in your construction project, use our Interactive Span Table to quickly identify the size and specification that you will require.

Distributor Map

JJI-Joists and our other engineered timber products are available through our network of distributors. Please enter your postcode in the space below to find your nearest distributor.

Design Tools & Support

As our Timber Systems Division has grown we have built an expert support team and a range of design software to make using the JJI-Joist system as easy and efficient as possible.

Knowledge Base

Knowledge Base is the new online hub offering support, guidance and expert advice to all registered users of James Jones' new JJI-Joist design software – JJI Design.

Carbon Data

James Jones was the first UK timber company to undertake PAS 2050:2011 carbon reporting so we can measure all the carbon locked up in our timber products.

CPD Courses

Our Timber Systems Division team offer face-to-face seminars on Engineered Wood Products covering all aspects of designing and working with JJI-Joists.

News related to
Engineered Timber

Our reputation for quality and service speaks for itself

Certification &

Find all the relevant compliance and technical downloads relating to sawn timber, JJI-Joists and pallets and packaging.

Tree to

Find out about the process all our high quality products go through before reaching our customers.

Span Table

Enter your span and load conditions and receive a list of joists suitable for your application: