Timber i-joist is an engineered timber joist which is used in the construction of floors and roofs for commercial and residential buildings.


I-Joists provide an alternative cost-effective solution to a traditional solid wood construction due to its lightweight and high strength properties, enabling longer and lighter spans with lengths up to 13m.

The design of the i-joists also helps create a quiet solution for floors with ‘squeak free’ joists and are ideal for flat or pitched roof structures. Once installed they can provide easy access for services such as wiring and plumbing. Our in-house team can also provide guidance on any hole/s which may need to be incorporated into the joists to cater for pipes and wires. This is recommended as calculations are required to determine the location/s and maximum size of each hole/s to ensure it doesn’t compromise our joists’ structure or key properties.


One key advantage is at Thomas Armstrong (Timber) Ltd, we supply all the relevant timber ancillaries’ items as standard. Depending on the timber product/s ordered, ancillaries items such as straps, hangers, timbers, truss clips, gable straps, valley gutters etc are delivered at the same time ensuring you have everything you need to complete the installation of our products on-site.



  • Easy installation and handling
  • Lightweight
  • Quieter Floor Solution – no squeaky joists
  • Engineered product that provides greater level of precision and accuracy
  • Prefabricated components mean reduced site labour costs
  • Easily transported and ready for installation on delivery
  • Cost effective solution
  • Increase dimensional stability over solid timber joist
  • Long continuous spans and multi-spans



  • House extensions
  • Self builds
  • Housing schemes
  • Barn conversions
  • Apartments
  • Student accommodation

Commercial buildings, including:

  • Schools
  • Nursing homes
  • Hospitals
  • Offices
Why choose Thomas Armstrong?

Thomas Armstrong (Timber) Ltd have been to be a leading timber roof truss manufacturer, servicing sites across the North of England and Scotland. To discover why to choose Thomas Armstrong (Timber) Ltd then click here for more information.

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Other Products Available

At Thomas Armstrong (Timber) Ltd, we provide a range of timber products to support you with your build project including:

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Supporting you with your build project
Thomas Armstrong (Timber) Ltd is part of the Thomas Armstrong Group, as we can provide a ‘one stop’ service as we have the skills, capabilities and knowledge to help support you with your entire build project. Other services of interest include: