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Community and Q&A

ZIP sheathing with asphalt felt: Window and door flashing

user-6651407 | Posted in General Questions on

We have ZIP Sheathing and have used the ZIP Tape for the Flashing around Windows and Doors.

Gearing up to start siding the home, will be using LP Smart Siding on the majority.

Our plan is to add a layer of Asphalt Felt first, then 1/4 plywood as the furring strips.
I have been searching for details on how to make sure the flashing is correct around the doors and windows, now that we are adding a layer of felt.

I might be overthinking it, but would rather be safe than sorry.

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  1. GBA Editor
    Martin Holladay | | #1

    There are lots of ways to flash window rough openings and door rough openings, and the various methods change depending on what type of WRB is used.

    In your case, it's not clear whether you are using the Zip sheathing or the asphalt felt as your WRB. Before you can come up with a plan for installing window flashing, you need to know where your WRB is.

    For more information on flashing windows, see this video series: Flash Rough Openings for Windows and Doors (8-part video series).

  2. user-6651407 | | #2

    We originally intended to have the ZIP as the WRB, and flashed the windows/doors accordingly. Now we are adding asphalt felt as the WRB.
    I am trying to find information regarding how to properly re-flash. Was hoping someone else has done the same and can offer insight or tips.

  3. GBA Editor
    Martin Holladay | | #3

    If you want to use asphalt felt as your WRB, you'll be depending on laps for watertightness. So at the window head, the asphalt felt needs to lap over the window head flashing.

    At the rough sill, the sill pan flashing needs to lap over the asphalt felt.

    The jamb details depend on circumstances -- but as long as the jamb flashing directs leaks to the sill pan, and as long as the sill pan directs leaks to the asphalt felt, you should be OK.

  4. user-2310254 | | #4


    I'm curious why you are topping the ZIP with felt. After all, ZIP is a premium product with an integrated WRB, and most people pay Huber's upcharge to eliminate steps in the construction process. If you are set on using asphalt felt, why not just use regular (and cheaper) OSB as your sheathing.

  5. user-6651407 | | #5

    Ok, I just found out they only want to add Asphalt Felt below the windows down. This is due to our stone cladding requirement. I thought they wanted to add to the entire home, but it is not needed under the lap siding. Our WRB would still be our ZIP.

  6. user-6651407 | | #6

    I am reading more articles, which state it might be added insurance to install the felt paper, to add an extra layer between the ZIP and the siding.
    If I were to ask for this, any special considerations? Could I keep the ZIP as the WRB and lay the felt over top?

  7. GBA Editor
    Martin Holladay | | #7

    There is no harm in adding asphalt felt on top of your Zip sheathing. When it's time to flash your windows and doors, however, it's important for the builder to know which of these two layers is the home's WRB. The flashing has to be integrated with the WRB, and it makes sense to be consistent.

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