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Prevent Basement Window From Leaking With the Proper Seal

Prevent Basement Window From Leaking With the Proper Seal

Windows in the basement are great — sometimes. They add light and make your basement living space seem less like a dungeon. In some cases, they provide a necessary and legal egress from the home in case of an emergency. But if your basement window is leaking, it may be more of a problem than a feature.

Leaky basement windows introduce water into your basement, which can destroy your carpet, walls, and property. It also creates mold and mildew, a dank and musty smell, and even can create problems with your home’s foundation over time. A leaking basement window is no joke, and it’s important for people to learn to seal a basement window correctly.

A proper window seal will help stop both air and water leaks. The seal around any window will degrade over time and need replacing, but this is especially true for basement windows that are often dealing with groundwater and potential foundation shifts that affect the shape of the window.

How to Seal a Basement Window

Woman sealing around window

Sealing a basement window is relatively simple, requires no major tools, and takes around 10 minutes per window.

You’ll Need:

  • Putty knife
  • Utility knife
  • Silicone latex-based caulk
  • Caulking gun
  • Damp cloth
  • A steady hand
  • Patience


  1. First, remove any old caulk from around the window frame using the putty knife. Loosen the caulk by sliding the putty knife under it and lifting gently. Peel the caulk away with your fingers.
  2. Wipe the edges with the damp cloth to remove any loose caulk, dust, or dirt.
  3. Insert your silicone-latex caulk into your caulking gun. Follow the directions on the caulk. A 45-degree angled cut on the caulk tip works best. Make this cut, angled down, with your utility knife on a hard surface.
  4. With the cut tip at a 45-degree angle, place it against the window seam.
  5. Squeeze the trigger of the caulk gun to release the caulk steadily. The caulk should be about ¼” or ½ cm wide and deep.
  6. Pull the caulking gun as you release the caulk until you have covered one seam in one long motion. Release the trigger and stop when you reach the corner.
  7. Smooth the caulk by wetting the tip of your finger and pressing and dragging it along the product, creating a u-shaped indentation. Wipe off any excess caulk with the damp cloth.
  8. Repeat this process for the other window seams.

Finding a Permanent Solution to Basement Window Leaking

Worker hand removing old window replacing the old wooden window,

Sealing basement windows will help prevent unwanted water and air from entering your home. Proper sealing will not stop window leaks permanently, however. If the grade of the ground or problems with the window well continue to direct water to the window, the seal will break down again. Often this happens because a building’s foundation shifts over time.

Basement Repair Specialists installs high-quality replacement basement windows, including glass block windows.  These glass block windows are available with vent ports, dryer vent attachments, and come in clear, frosted or wave patterns. They are mortared into place, and prevent leakage and the entry of insects and pests, and have great insulative qualities.

Leaky windows that allow water into basements can create many other problems for your footings and foundation. They also decrease your home’s energy efficiency and make you vulnerable to outdoor vermin entering the house. While window sealing is an excellent temporary or short-term solution, should you find yourself needing a more comprehensive fix, contact Basement Repair Specialists for a consultation.

For more information about your basement repair needs, visit our Basement Repair Blog.