GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Has anyone tried retrofitting with “Gapotape?”

Lee_roy155 | Posted in General Questions on

My brother in law is retrofitting after his builder installed PIR board and they got into an argument, some of the sheets are falling out and most of the stuff is nailed in (apparently there is even a technique to “nail it” properly according to some videos online, why is that even a thing?) and the space between the rafter and board is huge. He’s not reinstalling the insulation but instead is doing it himself and putting this foam tape around the sides called “gapotape”, that attaches like a band aid and expands in and out over time, they don’t have much stuff online besides an animated YouTube video so I was wondering if anoyone has heard of it and knows if it works or not? Also how long does it take to apply and should I just tell him to do something else or get the whole thing redone maybe even with a different type of insulation? Any reply helps, cheers guys.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Peter Yost | | #1

    HI Lee -

    This is basically a manufactured version of "cut-and-cobble." Just seems like an amazing amount of work to avoid all the benefits of continuous rigid insulation.

    I will bet that this approach and the tape are not cheap in terms of materials and labor so not exactly a strong thumbs up from me...


  2. gapotape | | #2

    Hi Lee,
    A customer of ours pointed me to your question so hopefully I can help.. We have a number of installs & case studies from listed buildings / loft converstions / new build and retrofits to buildings that have already had a refurb and the panels are loose or cracks have appeared in spray foam..
    To cover the point made by Peter, yes there is additional labour and cost but you need to look at the actual performance of what is being installed, not every instance can you have the insulation over the face of rafter and in most instances (in the Uk) it is a combination of a system (between and over/under) to achieve desired Uvalue. To do so correctly the entire system needs to work, tipping the hat to the old way of “cut and cobble” there are inherent flaws as there is no allwance for rather shrinkage and movement of rafters and general buidling movement during the year. Our product has been tested in the real world and we have seen a disparity in performance of upto 80% (no typo) in declared performance vs on site performance so you do the value engineering on that and you can see that the additional cost vs performance is a moot point..
    We don’t hide that we are a performance product, if cost is an issue then we advise on looking at a different system but if its results you are after them please visit our site and read through the test material in the download section.. Our technical team are on had to show you the best way to get value at install but if you already have the boards installed (poorly) then applying Gapotape will be the most effective way to achieve its full performance.. I would say that though wouldn’t I..
    Happy to help where we can.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |