Newly Install Windows Leaking
We installed all our windows over the last few weeks in our new construction house. We have exterior foam and outie windows. We did the flashing exactly like Matt Risinger did in this video except we haven’t installed the head flashing: https://youtu.be/W5zR3GeUjG4
Because we don’t yet have our head flashing we left the sheathing exposed at the tops of the windows. I’m hoping this is where the water came in but I am not sure. About half of our windows leaked after the deluge of rain and wind last night.
I have a ripped piece of beveled siding the width of window on the sill for the slope which has zip stretch tape over it. You can kind of see it in the pictures.
My question is, without the head flashing and foam above the window, is it not surprising that it leaked? Can flashing tape alone be expected to keep a window from leaking? I just don’t want to install head flashing and button up the wall only to find out it is continuing to leak.
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Your Zip tape does not appear to be properly rolled or squeegeed. It will stick with hand pressure but it won't stand up against water unless the adhesive is fully activated, which requires more pressure than you can exert with your hand.
Ideally sill pans would also have a backdam, which probably would have masked this problem. Water is likely getting onto the top of the jamb and running down the sides; otherwise it wouldn't have flooded over the sloped sill. Unless, that is, you're in a very windy location where the pan can't drain to the exterior due to wind pressure.
Hey Michael,
Thanks for the reply. We did roll the tape with the j-roller. It does look like there’s bubbles where the zip tape is going from the buck over the window nailing flange in the picture but it’s all rolled pretty well. We will try to reroll even so. We are in a very windy area on a hill top. It’s definitely possible wind wasn’t allowing the water to drain out. If trimmed out properly, would that prevent wind pressure?
I could try to do a back dam with some caulking. Or would there be another good method for a back dam with windows already installed?
OK that's good to know. A high percentage of builders don't think rolling is necessary but it really is.
I've only seen wind preventing windows from draining twice; both were directly on the Maine coast, on top of a bluff, which accelerates wind speed. One had conventional windows and even after removing all siding and adding a rain screen gap that should have allowed drainage, we eventually had to resort to caulking the windows shut.
The other project has windows similar to yours. We caught the issue early and ended up installing the exterior sill above the weep holes, draining into a wide rainscreen gap, which isn't recommended but solved the problem.
It might be a blessing that you don't have a back dam; you wouldn't want that amount of water getting to the sill pan on a regular basis. But I'd probably add a rip of 1x1 or 1x2 and use a sticky tape like 3M 8067 or one of the European tapes to make the back dam. Or, ideally, peel what you have off the framing if it's not completely stuck yet.
Why is there water on the inside of the window vinyl itself? It looks like it came from the top of the inside of the window.
Dry everything off. I know it sounds crazy, but you have to duplicate the leak with a spray bottle or even a hose to pinpoint the leaks.
That was my question too. The exterior doors aren’t installed yet so maybe wind was driving the pooling water into the windows. We will have to pull out the hose and do a leak test.
With the doors open, especially if they are on the lee side of the house, there could have been a very strong negative pressure inside which would draw water in through the drainage gap and any other opening.
A first point is that the windows only have an exterior seal, and no interior seal. Having both an exterior and interior seal is critical for keeping out wind-driven rain from the window-to-wall interface, creating a "weeped/drained two stage joint." Joe Lstiburek writes all about this concept in this article--check out the "cup in the rain" analogy.
BSI-004: Drainage, Holes and Moderation
https://buildingscience.com/documents/insights/bsi-004-drainage-holes-and-moderation
In short: expecting a window to keep out wind-driven rain with only the exterior line of waterproofing is like expecting to win a drag race while towing an Airstream. With the current condition, all of the wind pressure is pushing through any imperfection it can find in the outer ZIP tape seal. With a two-stage joint, minimal pressure occurs across the outer joint, so there's less force pushing water into the drained gap.. and even if it gets through, it should be weeped away.
In terms of retrofitting a backdam: one option is to cut a piece of ~3/4" x 3/4" aluminum angle, and stick it down with sealant to the ZIP tape sill pan. It also requires some fiddly detailing at the ends. Also, don't forget that an interior air seal needs to join the sill pan to the window unit. More on sill pans here:
Info-302: Pan Flashing for Exterior Wall Openings
https://buildingscience.com/documents/information-sheets/pan-flashing-for-exterior-wall-openings
Hannaiiii,
Like Kohta I’m not terribly surprised the windows leaked at that stage. Apart from the internal air-sealing he mentions, and lack of a head-flashing, they also aren’t yet covered by the cladding, which is their primary layer of protection. A rain-screen cavity also helps alleviate both wind-blown rain, and pressure imbalances.
Thanks everyone! The cup in the rain makes a lot of sense. I feel better about it now. Hopefully we don’t get anymore crazy driving rains until we get our trim and siding up….
My next question is, for the head flashing, we had planned to do it just above the windows. Should we also do it above the trim? If so would the flashing above the trim need to go back to the WRB? I saw this video (https://youtu.be/PPYhcOcLcvE?si=eAxV-xxkbvOQNu7J) where a slit was cut in the foam over the trim and the head flashing stuck into that slit. Would that be an appropriate way to do flashing above the trim (if required)?
Hannaiii,
Where the head-flashing goes depends on whether the window trim will be installed directly onto the sheathing, or is mounted on top of the cladding. If it’s the former the flashing goes above the trim, if the latter then it goes below.
If you are using a rain-screen remember that the head-flashing needs to run back behind the furring strips, and needs end-dams.
Flashing above the trim is required if the trim is wood and it's not a bad idea for other materials. Inserting a flashing into the foam as shown in that video really only works if the surface of the foam is the WRB. Otherwise, water running down the face of the WRB will bypass the flashing.
I second the concern of NyNick above that there is water showing high on your windows in the photos and that suggests the leak is farther up and not necessarily backing up the sill dam. Of course both are possible. Also, to me that's a LOT of water, not a little bit. While I agree that installation of the vented and drained siding and trim will help, I would not be comfortable with leaks like this. Water testing with a hose can be fast and cheap. If the house is tight enough for a blower door, depressurizing the house during testing can simulate a pretty substantial wind and it really activates small leaks. Work slowly with the hose from the bottom of the window to the top and even the walls above so that you can see exactly where the wall starts leaking. You photos don't show it, but if these are first floor windows in a 2-story wall, the leaks might be coming from the windows above. Check the back side of the sheathing above the windows for water during spray testing and make sure to wet the wall for its full height. Your leaks may actually not be related to the windows at all.
Most of my windows had similar leaks at the same stage of construction and have been fine without changing the flashing.
If it would make you feel more confident haul some 5-gallon buckets of water to the site and use a watering can to wet down the windows and check for leaks. My guess is without the wind the water will not get in.
Walta