Joisties | Steel Underfloor Insulation | How To

Each Joisties board is 1-metre in length. There are 20 Joisties in each box, which covers 20 lineal metres of joists.

First, work out how many Joisties you need. Measure the length of joists in your steel framed floor. Multiply this by the number of joists to get the total lineal metres required. Make sure you check for areas with different length joists.

It’s helpful to draw a diagram showing the length and number of joists in each floor section.

What you will need:

  • Adequate Joisties to cover all joists.
  • Utility knife.
  • Tape measure.
  • Pencil.
  • Diagram with dimensions of floor joists.
  • 2 Joisties Fitting Tools.
  • Joisties Adhesive.
  • Polyester insulation rolls to fit between joists


  • You need at least 40cm of crawl space to install underfloor insulation.
  • Use a sharp utility knife to cut Joisties to length, or to fit around pipes and wires.
  • When trimming Joisties, lay another Joistie over the top of the Joistie to be trimmed, to use as a guide and create a neat square end.
  • Use Joisties Fitting Tools and Joisties Adhesive for best alignment and installation.

How to videos:

There are 5 parts to installing Joisties. We have broken each part out into a separate video to make it as easy as possible for you to undertake your own installation, just like a professional.