FortiFlash to flash window bucks
bongo30
| Posted in General Questions on
We are building a new home in Zone 4, and using exterior insulation under our siding. Hence, we had to use window bucks. Our contractor flashed our windows with Henry’s FortiFlash. He also intends to flash the windows with Zip flashing tape after Tyvek is installed. Is this an ok installation for FortiFlash? It seems not to stick as well as other tapes we had used. Any compatibility issues with Zip tape over it? How would you terminate Tyvek into it?
thank you,
Lana
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So we came back two days later, and FortiFlash is already peeling off. I’m thinking about using either Zip tape or 3M 8067 to tape the edges (as that’s what we have on hand) but cannot find anything in terms of chemical compatibility between FortiFlash and acrylic tapes. Does anyone know? Thanks.
bongo30,
I don't know much about flashing bucks having never used them, but it makes no sense that the FortiFlash isn't sticking, and it shouldn't need reinforcing with other flashing tape. Something has gone wrong with the installation. Maybe not rolled?
Thank you Malcolm.
I have been researching this issue for hours now, and the closest I had come up with this video where he uses Tyvek tape for the edges. https://www.youtube.com/watch?v=H7S0Th8g3U0
I’m not sure if it’s the install or the product. I tried rolling it myself with J-roller and it sticks initially but then slowly separates. I just don’t know what else to do. It’s asphalt based so I don’t think it can be easily removed, and I’m afraid to use a tape which could chemically react with it.
Found another link about FortFlash not adhering. https://www.jlconline.com/how-to/exteriors/testing-flashing-tapes_o
So I guess the question now is how do we fix this? If anyone has any suggestions? Thank you.
Modified asphalt adhesive need continuous pressure to adhere, slow process so rolling it won't do it. On a vertical surface or under an overhang it will separate. There are some primers you can get that help with adhesion and can staple the edges to keep it in place. Not the best product for flashing tape origami or anything more complicated than a simple rough opening sill pan.
The good news is that acrylic tapes will stick over the flashing and you can use it to hold it in place and to tie it into your WRB. The WRB on top of the windows should lap the peel and stick and the bottom it should go under the fortiflash. In some ways it is good that is separating so you can slide the house wrap under it. You can use an acrylic tape on the bottom if you can't get the WRB under it but you end up with reverse laps. Reverse laps tend to be not an issue unless you have reasonable rain and overhangs but should be avoided if you do something silly like no overhangs or open cladding.
Thank you Akos! I think this is similar to what our contractor was trying to explain to us. They intend to bring Tyvek all the way to the window bucks and tape it with Zip tape.
My question is — at the top of the windows if Tyvek overlaps FortiFlash, it shouldn’t be a concern if FortiFlash separates from the plywood underneath Tyvek?
My second question is chemical compatibility - are acrylic tapes ok to use with asphalt based FortiFlash?
This is our first build, so we are new to all this. Trying to do everything the right way and learning a lot along the way. Thank you so much for your help!
So it looks like the the windows were installed with reverse lap on the bottom only, under the window buck. It was properly lapped elsewhere. Looking back, they should have installed the bottom roll of housewrap before they even flashed the windows rough openings with FortiFlash.
Is this something I need to press to be redone? Or just let it go at this point? The reverse lap is under the window buck, how much water gets there? We are in New York, so do get a fair amount of rain, and our overhangs are only 12”-16”.
Thank you.