# window flashing over tar paper



## olsonjh (Sep 10, 2012)

I recently had to remove an entire bay window.....or rather bay room as it starts at the floor and runs the entire length of the wall to the ceiling..extends about 3 feet off the house and aprox. 12 feet wide at the house....due to extreme rotting....I completly reframed and sheathed the entire thing.....I didn't think I wanted to buy an entire roll of house wrap to due a fairly small section of house so I just tar papered the walls...I am installing three separate windows and my question is if the adhesive window flashing will stick to the tar paper and if I can use the same method to flash the Windows as if i had used house wrap instead......thanks for any input in advance


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## Windows on Wash (Aug 30, 2011)

Theoretically that is correct but in the retrofit applications I prefer sticking it to the substrate where it can really hold on to something that it can bite into.


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## olsonjh (Sep 10, 2012)

Ok.....well my next question is if you place it under the moisture/weather barrier ( minus the top of the window of course) doesn't that defeat the purpose as moisture will still run under the tar paper and rot out the wall


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## Gary in WA (Mar 11, 2009)

I agree (with Window's post); http://www.buildingscience.com/docu...od-frame-wall/?topic=/doctypes/researchreport
If a weather-side, add another layer of paper with joints/laps staggered, if it rains much there.
Head flashing; http://www.buildingscience.com/docu...penings/files/bscinfo_302_window_flashing.pdf

Gary
P.S. Welcome to the forums!


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## olsonjh (Sep 10, 2012)

If there is a different method could you please explain.....


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## olsonjh (Sep 10, 2012)

Ill check out your link....


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## HomeSealed (Jan 3, 2008)

olsonjh said:


> Ok.....well my next question is if you place it under the moisture/weather barrier ( minus the top of the window of course) doesn't that defeat the purpose as moisture will still run under the tar paper and rot out the wall


No. The idea is to have everything lapped properly. The inner most layer of any material should be overlapped by each subsequent layer above it. By putting the flashing tape under the tar paper/wrb, any moisture that did runs down the wrb will not get in past that flashing tape. If you had the tape on top the wrb, the water has a clear path to get into the opening should the adhesive ever fail. That would be akin to attaching metal flashing to the exterior of the siding... and incidentally, I have seen that done before.:laughing:


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## olsonjh (Sep 10, 2012)

Ok I understand the idea of overlapping each layer so moisture runs over and onto the face of the layer before that and not behind and down between the osb and weather barrier.....im just wondering.....since I have already tarpapered the wall....to the window opening.....if I can use the adhesive sill pan on the bottom and will it stick to the tar paper? And then overlap it with the side flashing...and if it will stick to the existing tarpaper....then overlap those with the head flashing and finally flip the tarpaper on top down over the head flashing? .....what confused me was when the first reply said to stick the flashing directly to the osb....so peel back the paper on the sides and flash the window? Obviously the sill pan will overlap the tarpaper....then overlap with the side flashing and then lay the tarpaper back across the top? The head flashing will have to overlap both the side layers and flashing and then also covered with the top layer of tarpaper?? Im well aware of the idea of how to shed water im just mostly wondering how modern housewrap methods and systems work with old school tarpaper.....I apologize for making this sound more complicated than it is haha....I thank you guys for your patience and answers...also im curious about your views on housewrap vs tarpaper.....like if you cut housewrap at the head flashing you tape it ....if you cut the tarpaper do you then run another layer of paper from the cuts to the top of the wall....or at least to and then under the next layer??


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## HomeSealed (Jan 3, 2008)

olsonjh said:


> ..since I have already tarpapered the wall....to the window opening.....if I can use the adhesive sill pan on the bottom and will it stick to the tar paper? And then overlap it with the side flashing...and if it will stick to the existing tarpaper....then overlap those with the head flashing and finally flip the tarpaper on top down over the head flashing? ?


Sounds like you've got it... To answer your other question , the tar paper= house wrap for this purpose so treat it the same. Yes, the flashing tape will stick just fine if not better than it does to most housewraps.


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## Duckweather (Mar 26, 2012)

I would check the fine print on the product. If it is made by Grace it has chemicals that will dissolve the asphalt in the paper. Look for if it says apply to wood. (Grace also had a warning not to inhale the vapors as you peeled the backing off.)


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## olsonjh (Sep 10, 2012)

Alrighty thanks guys......I appreciate the replys


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