Home Improvement Articles

Why is My Window Leaking ? Common Causes and Solutions
When you have water leaking in the top of your first floor windows, and you have second floor windows above with a vinyl siding exterior, there is a pretty good chance, your window and siding contractors made some serious errors in the installation of the exterior cladding on your home. We recently received a call from a concerned customer regarding water leaks in their first-floor windows, particularly at the top side. If you are experiencing similar leaks with windows both above and below, there are several important factors to consider through diagnosing this common home problem.
Monday, July 3, 2023

House Wrap and Flashing:


Firstly, check if your house has a proper house wrap or if it is built with straight OSB plywood. Older constructions may lack the Tyvek layer behind the siding, which is now a requirement. Look for flashing strips at the bottom corners of the windows as well. These strips play a crucial role in preventing water from seeping behind the J-channel. By extending the flashing onto the nailing flange of the siding below, any water that finds its way behind the J-channel will be directed outside, through the weep holes located at the bottom of the siding.

 Window Installation:


Proper window installation is essential for preventing leaks. Verify if the window is correctly flashed to the house and if it is layered properly with the house wrap, drip cap, and other necessary components. Ensuring these elements are installed correctly will prevent water from seeping behind the siding and causing leaks.

 Identifying the Source of Leaks:


To begin addressing the specific issue at hand, the first step is to remove any shutters that may be obstructing your view. Once the shutters are off, proceed to peel back the siding around the first-story windows to expose the problem areas. During our investigation, we observed that the Tyvek was not getting behind the aluminum flashing, revealing the bare wood. The water staining on the Tyvek seemed to be coming from the bottom corner of the J-channel, indicating a buildup of water. Ideally, the house wrap, Tyvek, and paper layers should include a flashing layer over the nailing flange of the window to prevent water from seeping behind the siding through the J-channel. We noticed streak marks where water had been allowed to pass behind the window, onto the frame, and eventually into the house, causing the leaks.

Similar issues were found on the other window. It seems that either the original installation was better, with proper sealant behind the nailing flange, or there was a previous repair on one side that wasn't performed on the other, leading to the current leakage. When the layers are not correctly aligned, leaks are bound to occur. For example, if the Tyvek had been two inches longer or if different measures were taken with the paper layer, the issue could have been avoided.

Correcting the Layers:


To rectify the situation, the correct installation of the layers is crucial. If the paper is only behind the window, it is necessary to remove the tarp Tyvek over it. This will allow for a direct approach to the other layers, bringing us closer to the desired result. Using blue skin window tape against the nailing flange of the window and onto the OSB behind it, followed by Tyvek tape across the J-channel, will help seal the layers and ensure any water that comes down is directed to the outside. Once the layers are properly fixed, the siding can be reinstalled.

 Completing the Repairs:


After successfully reconstructing the lower half of the window, adjust the aluminum scaffold to extend higher. Continue bringing the siding up a few more courses and install flashing underneath the bottom of the windows where the J-channel is located. This step ensures proper drainage onto the nailing flange of the vinyl siding. Correctly positioning the Tyvek, with the J-channel placed over it, prevents water from seeping between the J-channel and the window flange, avoiding any potential damage. By adhering to these steps, water should be pushed to the outside and allowed to escape through the weep holes.

 CopeBUILT Proper Head Flashing 


We recieve over 100 calls per year asking us to help stop Exterior Water Leak mysteries that are destroying local homes. One of our most popular videos on Youtube is titled "why is the top of my window leaking?".  If your windows are missing this critical piece of head flashing, you can be unknowingly allowing expensive water damage to infiltrate and destroy your home. This video explains the provisions we use to protect your Forever Home and what a proper head flashing looks like. What Problem can we SOLVE for you?


Water leaks from the top side of windows can be a complex issue, but by addressing house wrap, flashing, and ensuring proper window installation, you can effectively prevent future leaks. It is important to fix the layers correctly, ensuring that water is directed outside and not allowed to seep behind the siding. By following these steps and conducting a thorough inspection, you can eliminate leaks and maintain a dry and secure home. If you require further assistance or encounter any similar issues, our team of experts is available to provide support and ensure the long-term integrity of your home.