How to Seal Basement Windows

a basement window
  • 3-4 hours
  • Beginner
  • 35-100
What You'll Need
Caulk softener
Polyurethane caulk
Putty knife
Small dust broom
Small dust pan
Trash bag
Old wet rag

No matter if you use your basement as a storage facility or as a living quarters, drafts at the seams of your basement windows can rob your home of heat or cold, resulting in an increased utility bill.

Sealing your basement windows is easy to do yourself and can save money on your monthly utility costs. With the proper materials, technique ,and instruction, you can make your basement an energy efficient domain by following these steps.

Step 1 - Inspect Windows for Drafts

To find air that is seeping into your windows, you hold a lit candle close to the seams of each window in the basement. If the flame of the candle bends, it is an indication of a draft coming into your home. It is a good idea to check the condition of the caulk both inside and outside your windows.

Caulking on the outside of your windows will dry out over a period of time due to the heat during summer months. Evidence of an abundance of gaps and cracks in your caulking is a signal to re-caulk your basement windows.

Step 2 - Remove Old Caulk

To make removing the old caulking from your window seams easier, wait 2 hours after applying the caulk softener to the windows. Doing so allows the softener ample time to work on the caulk. After the time has elapsed, use your putty knife to remove the caulk from the windows.

Make every effort to remove as much of the old caulking as you possibly can in order to ensure that the new caulking can adhere properly to a clean surface. After removing the caulking from each window, use the small dust broom and small dust pan to sweep up the caulking and dispose of it in the trash bag.

Step 3 - Prepare Areas To Be Caulked

With a wet rag, wipe the areas around each window to remove any debris from the old caulking and excess caulk softener. Doing so helps the new caulk stick to the surface. Ensure that the areas are dry before applying new caulk.

Step 4 - Apply New Caulk

The number of windows you will be caulking determines the number of tubes of polyurethane caulking you will need. One tube is sufficient for one window. You will be caulking the inside and outside of your windows.

WARNING: When caulking the inside of the windows, be sure that there is good ventilation in the basement by keeping the door open to the area.

If necessary, place a fan facing the open door to help with ventilation. Apply the caulking in a steady motion along the seams of the window. When you encounter areas with large gaps, slow your motion to ensure the gap is sufficiently filled. Once you have caulked the window, wet your finger in a small cup of water to smooth the caulking. Allow the caulking 15 hours to dry.