When addressing air leakage around an exterior door, the underside of the threshold is often overlooked.

As homes shift with weather and age, gaps form beneath the door threshold. Hidden underfoot, these gaps are difficult to see.

Eventually, moisture seeps in, and the issue becomes more evident. By then, damage to the underside of the door jamb may be extensive, while the years of accompanying air leakage can be costly.

Installing a foam threshold sealer beneath the door threshold will prevent damage and create a weather-tight seal, helping to keep weather and water at bay. Tite Seal makes a durable self adhesive foam threshold sealer that is perfect for the job. The sealer boasts an almost irremovable adhesive, is about a 1/4-inch thick and comes on a roll approximately 5 inches wide and 42 inches long.

Step 1: Remove the existing door threshold. Thresholds are typically held in place by a series of screws. These screws are often located beneath the rubber seal that runs along the center of the threshold.

Step 2: Clean the area beneath the threshold. Remove any debris, and fill gaps with a waterproof putty. Bondo lightweight body filler works great for most applications. Rockite Expansion Cement works well on concrete, and Durham’s Rock Hard Water Putty or Abatron WoodEpox are good choices to replace rotted sections of wood.

Step 3: Once the area beneath the threshold is clean, dry and smooth, measure the length of the doorjamb and add 1 inch to the overall measurement.

Step 4: Unroll the foam sealer and cut it to size, lengthwise.

Step 5: Center the sealer along the door jamb and allow the ends of the sealer to extend a half inch up either side of the doorjamb.

Step 6: With the door sealer in position, carefully peel away the release paper, a few inches at a time, pressing the seal into place as you go. Work slowly down the length of the door jamb until the seal is adhered permanently and the release paper has been completely removed.

Step 7: For larger gaps, a second layer of foam seal may be added atop the first layer. Remove the release paper before adhering the foam seal to itself.

Step 8: Reinstall the door threshold, pressing firmly to properly adhere it to the new foam gasket. Screw the threshold into place, and enjoy a more draft-free entryway.