• Whitehaven: 01946 518 800
  • Workington: 01900 844 200
  • Calderbridge: 01946 841 122
  • Barrow: 01229 845 300

We are open Monday – Friday 07:30 to 17:00 & Saturday: 08:00 to 12:00

Cumbria's No.1 Timber, Joinery and Tool merchants

JJI Joists

Jacksons Timber is a proud distributor of James Jones I-Joists, and has years of experience designing, manufacturing and delivering quality engineered flooring solutions to some of the countries top house builders, as well as all building projects, ranging from self builds right through to the largest structures.

A JJI-Joist is a composite engineered timber joist, combining 45mm deep high-grade finger jointed softwood flanges (C24) with a 9mm thick oriented strand board (OSB 3) web. Four flange widths are available at 45, 60, 72 and 97mm wide. These materials have different specific properties and by combining the two materials in this way to form a composite section you can use the strengths of each one where it is needed most. This results in the new section outperforming the individual materials that it is made from (the sum is greater than its parts) making it more structurally efficient. Using advanced technology these components are combined to produce an innovative alternative to conventional construction timber with many additional advantages.


JJI-Joists are designed to give a superior strength to weight ratio enabling the manufacture of longer and lighter structural members. The JJI-Joist, with a softwood flange:

  •  Is capable of spanning longer distances
  •  Is easier to handle
  •  Is easier to fix and nail
  •  Is less prone to splitting and delamination
  •  Is quicker to install
  •  Is extremely stable
  •  Reduces building maintenance
  •  Provides a less complex design solution
  •  Is simple to specify using superior software
  •  Has Part E compliant details available
  •  Is FSC/PEFC accredited
  •  Has a BRE Environmental Profile

JJI-Joists are available in a comprehensive range of sizes, designed specifically for the UK market, and in lengths of up to 12m. With Depths ranging from 145mm right through to 450mm and widths of 45mm, 60mm, 72mm and 97mm.

For full technical details on JJI Joists please reference the James Jones Website at: 



For further information, please contact our Workington branch:

Pitwood Road,
CA14 4JX

Telephone: 01900 844 200

Email: enquiries@jacksonstimber.co.uk