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How to Seal a Leaking Window

Updated April 17, 2017

A leaking window can be an annoyance for any homeowner. It can lead to increased heating and cooling costs, by allowing draughty air to pass through the cracks. Also, water can seep in and cause damage to the frame, sill and surrounding walls. Mold can be a result of this damage. For these reasons, it is best to repair the damaged window before the leak gets out of control. Early repairs can save time and put and end to the hassle of living in discomfort.

Remove the old window caulking from around the leaking area of the window. Use a putty knife to scrape the caulking off the surface. Also, scrape any dirt and debris from the area. Use a utility knife to cut the bad caulking from the good caulking. You will not have to remove all of the caulking from the window frame unless the whole frame is leaking.

Insert foam insulation into any holes or cracks that are causing the leak. Make sure the leaking area is dry at the time of insulation. Insert the nozzle of the insulation canister into the holes and cracks. Spray the insulation until it is overflowing from the hole or crack. Allow it to dry for the suggested time listed on the canister. Then, use a utility knife to cut away any excess hardened foam.

Spread a bead of caulking around the damaged part of the window frame and in any cracks or holes. Use the caulking gun to spread a bead that is approximately 1/8 inch wide. Use a damp finger to smooth the caulking into place. Apply pressure to the caulk, as you drag your finger along the bead. Allow the caulking to dry for the suggested amount of time listed on the packaging.

Things You'll Need

  • Rag
  • Utility knife
  • Putty knife
  • Silicone caulk
  • Caulking gun
  • Putty knife
  • Foam insulation
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About the Author

Kim Sarah has been a writer since 2000. Her work has appeared on NECN, WCTR-TV3 and in the "Torch" university newspaper, among other publications. Sarah received a Bachelor of Arts in communications from Worcester State University and a Master of Arts in journalism from Roosevelt University. She is also studying nursing and computer science at Indiana State University.