Wide or Narrow Joists: How to Make Your Insulation Fit

Sometimes you’ll come across extra wide or narrow joists under your floor.  Here’s how to make your insulation fit perfectly using our simple ‘Turn and Tear’ method.

Most commonly, standard joists have 430mm space between them, making our 450mm width insulation perfect for a nice snug fit. But, not all houses adhere to this standard sizing. Occasionally we come across whole homes that have extra wide or narrow joists across the whole home. But, most commonly, there are just a few rows of odd-width joists towards the edges of the home, because not all homes are the right size for neat row of standard width joists.

So what do we do if the joists are too wide or too narrow to fit standard 450mm insulation?

The answer is to ‘turn and tear’ your insulation. Our premium polyester insulation is designed to easily tear in one direction. This means you can create sections that are the exact width you need to fit between your wider or narrow joists.

Simply create the torn sections one by one and line them up between the joists, stapling as you go.

 

Here’s a breakdown of how we ensure the best thermal performance when up against wide or narrow joists:

  1. Rotate your insulation 90°
  2. Tuck the end into the joist space next to Joist A
  3. Measure to the outside edge of Joist B (this gives you a little extra wide for a nice snug fit)
  4. Tear the piece
  5. Press the new end piece in between the joist and secure by stapling as normal along the inside, bottom edge of the joist
  6. Pinch and staple the ends into the floor to ensure there is no room for air movement and rodent access
  7. Repeat to fill the whole space

Standard, wide or narrow joists: Here’s how we do it.

In this video, Maurice Beinat demonstrates how we install our polyester insulation using a stapling technique that’s exclusive to polyester.

You can learn more about why we recommend 450mm insulation for standard 430mm joist spacing by clicking here. You’ll also find information on how you can order custom width insulation if your floor joists are consistently 600mm apart.

Protect your home from unwanted heat gain in summer and prevent heat to escape in the colder months.

Get an Underfloor Insulation Now!