Taping Foam on Roof
![](https://secure.gravatar.com/avatar/3cc783a530612bb9fddcae4ada143824?s=52&d=https%3A%2F%2Fimages.greenbuildingadvisor.com%2Fapp%2Favatars%2F200x200%2Fa.png&r=g)
Redoing a low slope roof, 1-12. Installing 5″ of rigid foam (GPS) on the deck, wondering what the value of taping the seams would be. There will be two layers of foam, 2″ and 3″, laid with seams opposite each other. It’s an 1800 sq ft roof, so the taping isn’t a small job, on two layers.
The whole assembly is below, what would I gain for the extra cost/time of taping?
Flex Membrane, 3″ gps, 2″ gps, deck, 8″ open cell foam, vapor barrier, drywall.
Thanks!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb1.png)
![](https://www.greenbuildingadvisor.com/app/themes/greenbuildingadvisor/dist/img/modules/detail-library/thumb2.png)
Replies
Is the flex membrane your WRB? If so, you wouldn’t get a benefit taping both layers, only the top one would do you any good. Even then, it is basically a secondary WRB underneath the membrane. Most recommended assemblies I’ve seen put the WRB on top of the sheathing beneath the rigid foam.