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Community and Q&A

Flashing and Taping Existing Windows

megnchris | Posted in General Questions on

Hello again.  We are at the final stages of having our home re-sided in Hardie siding (we live in Ohio).  We previously had stucco, and after two separate instances of water intrusion, we decided to remove the stucco and get Hardie.  We also had new replacement windows installed 2 years ago (for clarity, the original windows’ nail flanges remain).  We have had the window company’s installation manager out to our home several times when we thought the windows were leaking (which turned out to be the 2nd time the stucco leaked), so he’s very familiar with our situation and is extremely sympathetic.

Our Hardie contractor’s crew installed capping on the windows, but in doing so they blocked (or caulked shut) the weep holes on the sills.  They’ve agreed this was wrong and are willing to recap all of the windows.  However, in the meantime we asked our window company’s installation manager to take a look at the capping.  He of course was in agreement that the capping was wrong, but he brought up another issue – since the stucco was in place when the replacement windows were installed in 2018, they couldn’t see how the nail flanges had been sealed/taped or how the house wrap was handled around the windows…..but after removing all of the stucco, the current Hardie contractor COULD see those details and ideally should have flashed/sealed/taped the windows appropriately.  NOW for the real question – can someone please define what would be appropriate for EXISTING windows, NOT a new construction?

I know that the nail flanges were not taped with flashing tape.  However, the Hardie Wrap (house wrap) was brought up to the edge of the windows and taped with Hardie tape to those nail flanges.  Is this enough?  There is flashing above the trim at the top of the window….it was not placed behind the Hardie wrap, but the top of the flashing was taped (again w/ Hardie tape) to the house wrap.  This tape isn’t anything special IMO….seems like packing tape but a little thicker and certainly isn’t very sticky.

We created a punch list for the contractor, and the window re-capping is a major component, but our contractor won’t agree on how to do it with our window company’s installation manager, and we’re reluctant to go against his recommendation (to clarify, window guy is suggesting that when they re-do the capping, they create a nail flange along the jambs that could be nailed to the sheathing then taped).  The contractor (who also installs windows but didn’t do ours) says they know what’s acceptable and what they did is correct.

We would love some advice, bearing in mind that 1.) We still owe the contractor 2/3 of the total bill, so now’s the time to get it done right, and 2.) we still have no drywall in 3 rooms of our home because of water intrusion and we NEVER want to go through it again (i.e., we want some peace of mind in knowing the windows aren’t going to leak).  Thanks!

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  2. Expert Member
    Akos | | #2

    The capping doesn't necessarily need to be redone provided there is a head flashing above it. That head flashing needs to go BEHIND the WRB not in front as it is in the small gable window. Not critical that close to your roof overhang but should be fixed for the windows lower down.

    I would also make sure they install proper step flashing for the roof of your entrance and a kickout flashing for the gutter there.

    With the siding completely removed, your install is pretty much how you do WRB after the windows is installed for new construction. See video here :

    This is pretty common practice, so there is no special details here. The WRB gets taped to the existing nail flange. The capping goes on and gets taped over the WRB. On the bottom it should be taped with 1/4" gaps to allow drainage. Top should go lapped by the WRB than taped in place. If you are in a place with a lot of rain, a kick out flashing above the windows might be a good idea.

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  8. Expert Member
    Akos | | #8

    They did things mostly right. Lot of installations show the top flange being taped to the WRB, which works but no ideal.

    WRB should always be lapped so that gravity moves water away from your structure and not rely on tapes. At least they did put in the head flashing.

    Since they are capping your windows, it should extend over the trim around your windows. It doesn't make sense to have two different materials there in terms of looks. Not sure why the did it this way in the first place.

    Make sure they tuck the capping above the top of the window under the head flashing. You don't want this new capping channeling water into your house again.

    At the sides it should just wrap around the trim and be caulked against the siding.

    Wrap the bottom the same way and caulk with 1/4" gaps every foot or so.

    Caulking over weep holes is a rookie mistake, so I would be careful with how they wrap it up.

    1. Deleted | | #9


  9. Expert Member
    Akos | | #10

    Your install falls into an unusual category. Normally when windows are replaced the trim is capped over because the trim tends to be in bad shape. When you replace the siding, the trim goes right up to the existing windows and there is no metal capping.

    It doesn't really matter how it is finished now, mostly up to your personal preference. It looks like the color match is pretty close so it is only noticeable up close.

    The hardie wrap is a WRB and it is mostly detailed properly underneath. The tape is not the best but as good as any of the budget acrylic adhesive based ones. As long as the flanges are taped, it should work (a better tape would have been nicer but I doubt it will cause water leaks).

    The important detail is the head flashing. Should be installed, slightly sloped to drain, the siding above it has a small gap and this gap is not caulked, there is an end dam (or caulked at the end) most of your water issues are dealt with.

    There is no need to bring the capping back to the WRB. Clap board siding is pretty forgiving, even questionable installs hold up well.

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