Insulating Posi-Joists

A Posi-Joist also known as a Metal Web Joist, combines the light weight of timber with the strength of a steel web.

The Posi‐Joist gives building designers the freedom to have a variety of internal room layouts without the constraints of solid and other engineered timber.

Their use is becoming increasingly popular in UK Construction and offers significant benefits to help speed up build time. Insulating them to remove the thermal bridge takes somewhat more consideration!

We’ve insulated numerous projects where Posi‐Joists have been used and we strongly believe that the only viable option is to use a spray-applied insulation such as ThermoFoam NexSeal or SucraSeal products.


Post Insulation image of Posi-Joists


Pre-manufactured insulation such as Rigid-PIR can offer serious constraints when insulating Posi-Joists and can often prevent the ability to install a seamless thermal layer that removes the potential for cold thermal bridging. Spray Foam Insulation overcomes this issue, allowing for maximum flexibility and helping to bridge the void between the metal angles through the centre of the Posi-joist.

Spray Foam insulation can be spray applied in between and through the centre of Posi-Joists to provide a seamless, monolithic thermal layer of insulation. This removes the potential for cold thermal bridging in areas where pre-manufactured insulation may struggle to reach.

Another major benefit of using Spray Foam for a Posi-Joist construction will be the time savings that you will enjoy, allowing you to focus on other areas of the project, safe in the knowledge that the insulation is taken care of.

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