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Where fluid applied meets WRBs

user-6610113 | Posted in Energy Efficiency and Durability on

Building in climate zone 3 in southern california roughly 20 miles from the ocean. 

We have a complex recessed detail that is best flashed with a fluid applied approach. 

My question is: if you fluid flash the window do you have to use fluid applied flashing for the rest of the wall?  If not how do you marry the WRB to the fluid applied areas?



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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Matt,

    I'd be interested to see a drawing of the detail to get my head wrapped around what you need to do.

    You could certainly use a fluid-applied product to flash the rough opening, but if you are going to be using a mechanically fastened housewrap for the WRB, you'll still want to detail it so that water is directed out to the surface of the WRB where ever it integrates with flashings, in other words shingle style laps. One of the biggest water management mistakes is reverse lapping the layers.

  2. jberks | | #2

    I think I get what your saying.

    You want to use a roll WRB like tyvek, for the walls but transition to liquid at the rough openings.

    As Brian said, the basic principal, in whatever you do, is to make sure the materials shingle down. As in the upper layers come overtop of the bottom one.

    To your questions:

    -if you fluid flash the window do you have to use fluid applied flashing for the rest of the wall?
    I personally don't think so. Of course It would be better to do the whole house in liquid applied. But I don't do it for cost reasons (but I put rockwool insulation overtop of my roll wrb)

    -If not how do you marry the WRB to the fluid applied areas?
    Flashing tape. I prefer 3M flashing tape, as a Canadian I can buy it on Amazon for a reasonable price. I think Americans have better access to siga wigluv and the like. I've never tried it so I can't say much about the differences. Other can comment if you ask.

    you liquid applied rough openings first. Apply give a good foot perimeter around the rough opening. After it dries, roll the wrb from the bottom up, cut 3" around the windows and tape the wrb to the liquid flash. Unfortunately, the bottom of the rough opening will not be properly shingled. If you don't want to rely on the flashing tape for longevity, or your OCD like I am, you can apply another layer of liquid flashing from the bottom of the rough opening overtop of the flashing tape and roll wrb. Make sure you don't seal the bottom of the windows if they are in at the time.

    Just my opinion. Others on here have more experience.

  3. AlexPoi | | #3

    Prosoco recommends a transition sheet under the window. You can reverse lap the wrb on the window top and side edges.
    See page 15 :

    EDIT: Page 19 also presents another approach for a new construction. Don't know what liquid applied flashing you are using, but I would check the manufacturer instructions.

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