Install nailing fin over rigid foam?

Having the house sided and have a question about nailing the new construction windows. Does the window fin get nailed through the 1/2 rigid foam or does one need furring strips?

Thanks!

Ken

You can technically nail through the foam but I prefer to build out the box for a secure hold at the fin.

Thanks WOW. Since techically you can nail through the foam I let him.

This is what the contractor did with the first few windows. Windows are Simonton 5500 with factory installed nailing fin and J channels.

Tyveked house including the window jams, remove tyvek from sill and up jam a bit to expose wood.

Installed membrane on sill and up the jams about 6 inches and wrapped out and over the tyvek. Of course on the verticals he overlapped the Tyvek over the membrane.

Attached rigid foam on house.

Nailed the nailing fin into the wood frame through the rigid foam.

Then attached membrane on top of the nailing fin and rigid foam to create a seal. Did not membrain bottom to allow weep, and attached the membrane in the right order on the sides and top so that it overlapped correctly.

When I asked him why he did not use sealant under the nailing fins he stated that with the J channels and the membrane there will not be any issues.

True? Am I going to have an issue with water infiltration? If so then wouldn't one need to apply sealant not only between the nailing fin and the foam, but also between the foam and the Tyvek? What about between the Tyvek and the sheathing? Seems that the foam does create many dimensions to the equation.

If sealant is prefered should he just do it on the remaining windows or should I insist he remove the ones he already did? Not crazy about the thought and I imagine there could be some damage by ripping the membranes off and pulling the nails out? But if there are serious issues with the install I guess I will ask him.

Thanks!

Ken

Edit: just had a thought...

State of house at beginning of current work. House has its original wood windows. House was built in the mid 60's. Back in 1989 the previous owner removed the asbestos shakes on the sides and back of the house and had vinyl siding installed. Front of the house had the original cedar shakes. There was no moisture barrier under the 1989 vinyl siding, just rigid foam, with one inch gaps between foam in areas! There were no membranes at all around the windows, nor any sealant between the house and the window.

The few windows that were just installed were on the sides of the house, which had the 23 year old vinyl siding. I have a ranch and there are only 3 windows total on the both sides. The window jams were fine on all three windows, but the wood faces on the window frames were a bit soft at the bottom. One sill looked like it was wet at one point, but no rot. The aluminum trim on that window had been pressed in at the corner and there was a small gap and I am thinking this is where the water got in. Looking at the stain on that sill I am thinking it was recently damaged.

Considering the fact that what is there now is so much better than what was installed 23 years ago I am thinking it should be okay. That is unless the old wooden windows were better about keeping water out than the newer vinyl windows with built in J channels.

It is preferable to caulk the flange but you should be okay with the sealed flanges via the membrane tape.

Don't caulk the Tyvek as you can trap moisture against the home in some cases.

Have him caulk the remaining units.

Thanks WOW!!! That was a fast response!

If it is bad to chalk between the tyvek and the sheathing then should the membrane not be attached directly to the wood on the top of the sill? Would it be better to have the tyvek between the membrane and the wood on the top of the sill?

Should I have him caulk between the Tyvek and the foam too?




I was just reading a thread on the web where two people were arguing on what should go on the house first, Tyvek or the foam.

My contractor stated Tyvek should go first. He was telling me to save money by not using the 1/2 foam at all as the 3 r value would not do much anyways. Most ppl here in the north east use the foam, so I spent the extra money on it. Hope it was the right decision.

I imagine that the caulk will ooze out the nail holes even if used sparingly. Wouldn't this make the membrane not stick to the fin?

Ken

I think that you might be slightly over-analyzing it Ken, although I commend your voracity in wanting to make sure that this is done right. By your description, the flashing detail sounds proper. Caulk on the flanges would have been one more level of "cya", but its not completely necessary.
The WRB (tyvek) should be on the outside of the foam in this case. I suppose it can work either way, but its function is as a Weather-Resistant-Barrier, so generally you want that directly under the siding to shed moisture away from all insulation and ro's.

+1

Ideally it should be sheathing, foam, window flange, tyvek.

You are fine the way you are right now.

Bottom line on caulking is simple. If Simonton calls for it on their "Installation Guidelines", they better be caulked! If not it could void your warranty. We must remember the Code is very specific on who is right and who is wrong. Installation Guidelines come with every window (hopefully). This is the bible for installing that window. As installers we have to follow these to a Tee. Good Luck!!!