New Windows Leaking? It's The Install, Not The Window

New windows are supposed to end your draft and water problems, not start them. But we keep getting called to Calgary homes where windows only a year or two old are already leaking. Almost every time, the window itself is fine. The install is the problem.

The Call We Keep Getting

It starts the same way. A homeowner replaced their windows, often chasing a good price, and everything looked great. Then the water showed up under the window. Drywall stains and soft spots below the sill. Damaged flooring along the wall. On two-storey homes, discoloration spreading across the ceiling of the room below.

By the time you can see any of that, water has usually been running behind the wall for a while. The stucco outside can look perfect the entire time. That is what makes these leaks expensive: they hide until the interior finishes start telling on them.

What A Proper Window Install Looks Like In A Stucco Wall

A window in a stucco or EIFS wall is not sealed by caulking. It is sealed by a layered system that has to connect to the wall around it. When we install or reseal a window in stucco, the job looks like this:

1. Open up the wall. Chip the stucco back far enough around the opening to actually work. This is the step cheap installs skip, because it is the slow, dusty, skilled part.
2. Use a window with a flange. The flange (the fin that runs around the frame) is what lets the window tie into the wall's waterproofing instead of just sitting in the hole.
3. Flash it properly. Flashing and reverse flashing, tied in with Blueskin, a self-adhered membrane, layered so that any water that gets near the frame is directed back out of the wall instead of into it.
4. Connect the new stucco to the old. The patch around the window has to bond into the existing stucco and its moisture barrier so the wall works as one system again.
5. Caulk last, as extra protection only. Caulking where needed is the finishing layer on top of a sealed system. It is never the seal itself.

What The Cheap Install Does Instead

Pull the old window out. Set the new one in the hole. Run a bead of caulking around it. Done by lunch.

No flange doing its job, no flashing, no membrane, no connection between the window and the wall's drainage. That bead of caulking is now the only thing standing between Calgary weather and your framing.

Why Caulking Alone Always Fails Here

Caulking is a maintenance product, not a waterproofing system. In Calgary it gets punished: freeze-thaw cycles, chinook swings that move the wall and the frame at different rates, and UV baking it all summer. It shrinks, cracks, and lets go, often within a couple of seasons.

When it lets go, gravity does the rest. Water tracks down the frame and shows up under the window, in the drywall, in the flooring, and in the ceiling below. The window gets blamed. The window was never the problem.

The Part Nobody Mentions: Tied-In Stucco Doesn't Crack

Connecting the new stucco and the window sealing into the old wall does more than stop leaks. It also prevents the cracking you see around so many replacement windows, where the patch and the original stucco move separately and a crack traces the outline of the install. A tied-in patch moves with the wall.

Who Is Doing These Installs

Some of this is volume window companies working to a price. A lot of it is the sealing work being handed to subcontractors, sometimes the stucco sub who was supposed to seal the window properly and did not. The homeowner has no way to see the difference on day one. Both installs look identical from the curb.

If you are getting windows replaced on a stucco home, ask one question before you sign: "How do you tie the window and the new stucco into the existing wall?" If the answer is some version of "we caulk it really well," keep shopping.

"A tube of caulking costs a few dollars. The drywall, flooring, and ceiling repairs behind a badly sealed window cost more than the proper install ever would have. The right way was never the expensive part."

Already Leaking? How We Find It And Fix It For Good

Leak chasing is diagnostic work, and guessing is how these jobs go wrong twice. Our process on a leaking window call:

• Assess on site. We look at the damage pattern inside and out and estimate where the water is actually getting in, which is often not where it shows up.
• Open it up systematically. We give you a plan to open the wall in stages, following the water back to its source instead of tearing off stucco on a hunch.
• Fix the source, then rebuild. Flashing, membrane, and stucco tied back into the existing wall, so the repair never leaks again. Not a caulking touch-up over the symptom.

Not sure which system is on your walls? Our guide to telling EIFS from traditional stucco takes 30 seconds. And for everything else that lets water behind stucco, see our stucco repair Calgary page.