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Why Is My Window Leaking?

(Hint: It’s Not Always About the Window)

Most people assume water leaks only happen with old windows, or when there’s some sort of product defect or installation mistake, but that’s not always the case. It can be a maintenance issue, which is one of the most common reasons a window starts to leak, or caused by something above the window. This can create a drainage point at the window, but the window isn’t the cause of the leak.

According to the experts at DunRite Windows & Doors, the location of the leak often identifies what’s happening.

Water in the window tracks

When there’s water in the tracks of a window, clearly visible from inside the home, what you are seeing isn’t actually a leak at all: it’s a sign you have windows with a weep hole drain system, and the window is working properly. When it rains, water sheets down the glass to the track below, then down through a built-in drainage system. You might see signs of dampness in the tracks of your windows, or if it’s filling up faster than it can drain due to heavy rain, you might even notice standing water.

This is normal, it’s just taking a little time for the water to work its way outside, exactly as it’s supposed to do.

Windows commonly have two types of drainage systems: sloped sills, where the sill is slanted towards the ground away from the house, allowing gravity to drain the water; and pocket sills, which have a u-shaped channel drain through the weep holes. Sloped sills may have weep holes, even though they work slightly differently than a pocket sill, and it’s important to keep the tracks clean on both types of window.

If you see water, don’t try to mop it up or place towels in the track, since that can wick water out onto the sill and cause damage. Instead, just wait it out, and the water will eventually drain through holes on the exterior of the window frame.

Go ahead and test this when it isn’t raining. Open the window, then go outside and stand in front of the open window. Slowly pour about a half cup of water directly in the track where the operating window slides. You should see it collect in the tracks, enter the frame, then exit from two or three small holes at the bottom of the window’s exterior.

If you see the weep holes aren’t draining, or water is rising above the tracks and spilling onto the sill, it’s an indication they might be clogged or blocked. Clean out any debris in the tracks and ensure the exterior holes are clear, then test it again. They should be able to drain properly.

Water between the panes of glass

While it’s completely normal to see touchable condensation on glass inside or outside the home, which is caused by humidity and rapid temperature changes, it’s not normal to see water or fog collecting between the panes of glass.

If you can’t touch it, there’s probably an issue.

Condensation between panes of glass indicate a broken seal, where moisture is working its way inside the sealed glass unit, and argon gas insulation has leaked out. It isn’t likely to damage the window, unless that window is made of wood, but it does mean the window is no longer providing the energy efficiency you expect.

If the windows may be covered by a warranty, the solution is to contact the windows and doors company who installed the window. You can also determine the brand of windows by looking for a manufacturer stamp or logo on the window, and call to see if they are covered. If not, or if you cannot determine the manufacturer, contact a glass repair company to replace the glass. They can swap in a new sealed glass unit with double (or triple) panes and argon gas, leaving the rest of the window intact.

You don’t have to replace the entire window.

Water leaking around the window

If you see water damage or leaks around the top or sides of a window that’s a replacement, not original to when the home was built, most often it’s a basic maintenance issue. If it’s been years since the installation, often the caulking (sealant, actually) has dried out, losing adhesion and cracking, which allows water to enter. It needs to be scraped out and replaced.

If leaks are in the corners of the window, causing damage to drywall inside the home, and it’s an old aluminum window, the problem may originate where the bottom track is screwed to the side leg of the frame. When installed, that joined area is protected by a sealant, which wears down over time. When this happens, and the sealant is allowing water to enter, you’ll see moisture damage (and possibly mold) in the bottom corners of the window sill.

If you’ve inspected the windows and don’t see any issues with sealant, they aren’t aluminum windows with potential sealant issues and the weep holes aren’t blocked, then check above the window. Water can travel down or across the wall and exit around the window, but have nothing to do with the window itself. You might find caulking that needs to be replaced or repaired around the fascia, roof or gutters, or debris might have caused the gutters to back up and overflow. Any of these things can reroute water where it shouldn’t go.

It’s a good idea for homeowners to inspect the interior and exterior of their windows and doors, and their roof, annually to catch any caulking problems early on.

If these inspections didn’t identify the source of the leak, there is one other situation to consider if the window is original to when the home was built—and that’s when the leak has to do with the construction of the house AROUND the window. This isn’t common, and it can take years, or even decades to show up.

When this is the case, replacing the window won’t help. You have to find and repair the source of the leak. It’s usually caused by missing or incorrectly installed flashing, Tyvek wrap that doesn’t extend over the nail flange of the window, or siding/stucco that’s been installed incorrectly. (Great video explanation below!)

If this is the problem, it may not be a fast or easy repair, requiring a contractor or third-party to get involved. Instead of a typical installation where we cut the window out of the opening, leaving parts of the original frame and nail flange (or fin) embedded in the wall, and sliding a replacement window over the cutout, the exterior wall needs the stucco or siding removed to reveal the interior wall where the window was attached. If that doesn’t reveal the issue, a contractor has to continue removing exterior walls until the issue is found and repaired.

Depending on where the leak originates, this can require a substantial amount of labor.  No homeowner likes that kind of estimate, but it’s certainly better than replacing the window in a leaking opening. The new window won’t solve the leak.

It might help initially, but not for long, since replacement windows are made to slide into a water-tight opening. Because it isn’t water tight, the homeowner ends up with the same leak on a new window, along with further damage inside the wall, possible insect and mold issues, and potential damage to the interior walls and flooring. Once the leak enlarges, the repair costs can get very, very serious.

And of course, this kind of leak is not covered by a product or installation warranty, since it’s not caused by the window.

DID YOU KNOW: Homeowners insurance may cover the repair if it was an issue related to original construction of the home, but not if it was a result of poor maintenance, neglect or normal wear-and-tear.

We’ve had situations where a homeowner adamantly insisted on window replacement after being told the issue was in the wall and above the window—either because their builder denied it was their fault, or because the homeowner was hoping the diagnosis was incorrect and the new window would solve the problem—but, of course, the leak reoccurred the very next time it rained.

The leak was still there.

This isn’t a good situation for either the homeowner or the installer. If you’re having replacement windows installed and the installer expresses concerns about a leak that doesn’t originate with the window, it’s best to resolve the issue before moving forward.

And if it’s a leak that just showed up on newly installed replacement windows? Naturally you’ll want to contact the installer. It might be a product or installation issue that needs to be resolved.

DunRite Windows & Doors has more than twenty years of expertise installing replacement windows and doors across the Phoenix Metro area, including brands like Andersen, Pella, Thermatru, Anlin, Milgard and Arcadia. Request an appointment today if you’d like a quote!

Published April 3, 2023

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