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Community and Q&A

Liquid Flashing Over Tar Paper

sunrisehomestead | Posted in General Questions on

Hello all-

I am starting a project in the coming weeks pulling some old windows out of a 60’s build cabin and replacing with some new sierra pacific windows. The WRB is likely old tarpaper. Because of the horizontal lap siding we’re hoping to not have to remove any siding to make this happen. I’ll end up cutting back the siding around the existing windows to make room for new trim.

I feel as if liquid flash might be a good candidate for this project to flash the rough openings, out onto the existing sheathing/WRB layer (tarpaper) and overtop of the flange to flash the flange to the WRB.

My question lies here-has anyone used liquid flash in a scenario like this with old and new? Has anyone reliably adhered to older tarpaper with liquid flash? Is there any particular sequence for flashing or basically just use the liquid flash to bridge from the RO/framing out onto the wall plane overtop of the tarpaper and we’re good? And then again overtop of the flange to the WRB?

I read somewhere that zip/prosoco don’t recomend using their liquid flash as a sealant behind the flange and we should use something different for that part like a quad max (this is what I usually use behind the flange).

Any advice on this would be super helpful!


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  1. sunrisehomestead | | #1

    anyone care to weigh in on this?

  2. GBA Editor
    Kiley Jacques | | #2

    Hi Nick,

    I looked around the site for a situation like yours but didn’t find anything. I’ll give your question a bump and point you to this post, which includes notes on specific liquid flashing products as well as links to many related articles (and reader comments) that might be useful: Liquid-Applied Flashing. I suspect it is a good product for your proposed use, and look forward to seeing what the pros say.

    1. sunrisehomestead | | #4

      Hey Kiley! Thanks! Hopefully someone chimes in! I have seen folks pull back the tarpaper, apply liquid flash, lay the tarpaper back down embedded in the wet liquid flash, and then flash the openings out onto the face of the tarpaper. I called ZIP tech support and they said they haven't tested the liquid flash product on tarpaper but recommended doing tests of my own. I actually really like the ZIP liquid flash product. It is super durable and one of the most elastic products I have encountered. I suppose if zip has no recs or testing on tarpaper and prosoco does maybe best to go with prosoco since its been proven. I'd still like to learn more from others on general methods, compatibility with tarpaper, and nail fin-using another sealant vs. using the same liquid flash product as the rough opening to adhere the nail fin to the wall.

  3. user-2310254 | | #3


    I would call the technical support line at Prosoco (800-255-4255). They must of encountered this issue a few times.

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