How to seal an exterior door from rain

Water seeping through the cracks around or below an exterior door can cause significant and expensive damage to door trim, carpet, tile, and even the foundational structure of the floor and walls. Fortunately, preventing moisture from entering through door cracks is relatively simple and can also improve the energy efficiency of your home. That saves you money in fuel costs and potential damage, and saves the earth by depleting less fossil fuels.

Find the leaks. Before you seal the door, you'll need to determine exactly where the leaks are. Anywhere air can get through, so too can water. To test for leaks, take a piece of thread in your fingers and let it dangle in front of the crack along the edge of the door. Slowly move your hand around the full perimeter of the door and note where the drafts are entering by paying attention to the movement of the thread. Keep in mind that the thread may be drawn toward the door or blown away from it; the direction is irrelevant. Movement in either direction indicates air flow.

Measure the sides and the top of the door frame carefully.

Cut self-adhesive foam weather stripping to fit the sides and top of the door frame. Each section of weather stripping should be cut in a single piece--one for each side and one for the top, bringing the total to three. Inaccurate measuring may require using two or more pieces on a single side, which increases the likelihood of leaks.

Wash and dry the moulding of the door frame to prevent any dirt or grime from interfering with the adhesive on the weather stripping.

Peel the backing away from the self-adhesive foam weatherstrip and adhere it to the inside of the door frame.

Measure the length of the door across the bottom.

Cut the door sweep weather stripping to the exact size of the door. Door sweep weather stripping is different from the self-adhesive weather stripping: It attaches directly to the door by way of a metal groove that slides onto the bottom of the door.

Slide the sweep onto the bottom of the door and lower or raise the sweep for maximum efficiency. If the gap at the bottom of the door is significant, for example, you may need to lower the sweep in order to seal the leak. If, on the other hand, the gap is small, you may need to raise the sweep in order to ensure proper door operation.

Screw the sweep to the door. The groove on sweep weather stripping comes pre-drilled, so determining screw placement is easy. Make sure, however, that the door is closed when you screw the strip on; otherwise, it might not fit right.

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