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  • Writer's pictureMatt Weber

Three Ways to Seal a Door

Conditioned air wasted through leaky doors can drive up power bills for even the most energy-efficient HVAC system. All the small gaps and unsealed joints in a leaky house can add up to the equivalent of an open window.

A poor weather seal can leave a substantial gap between the door and the jamb. Can you feel a draft inside even when an exterior door is closed? A general rule of thumb: If you can see light around the edges of a closed door, you have a problem.

Making Repairs

The plastic weather-stripping had deteriorated around the exterior door shown in this article. The caulk joints surrounding the door had also begun to crack and detach.

My first step was to remove the old stripping and carefully cut out the failing caulk bead with a utility knife.

One trick to removing caulk: Use a razor to cut along the opposite edges of the bead. Once the bead is detached along the sides, the whole thing often pulls out of the joint like a rope. You can cut out the leftover material with the razor.

Use a paint scraper to remove any remaining film that will interfere with the adhesion of new caulk.

#1 - Start with Insulation

For new installations or remodels in which you can access the interior of the door frame, take the opportunity to seal any gaps in the framing with spray foam insulation. Spray foam stops air and water intrusion through the building envelope and creates a thermal break to reduce heat loss.

When using spray foam to seal around windows and doors, it’s important to choose a product specifically labeled for “Doors & Windows,” which utilizes a low-expanding foam. Standard spray foam can expand so much that it warps the jamb or frame, which can then impede the opening and closing of the door or window. A low-expanding foam will fill gaps without the problems of over-expansion.

#2 - Apply Caulk/Sealant

Seal all seams and joints around the construction. The more elaborate the trim is around the door, the more seams you’ll need to caulk. All these smaller gaps can allow substantial heat loss during winter, and loss of cool air during summer.

Make sure to use a high-performance, exterior-grade sealant that offers reliable adhesion, flexibility and elasticity to accommodate the natural movement of construction materials as temperatures fluctuate. Remember that not all sealants are paintable, so check your product label if you plan to change its color.

For gaps wider than 1/4 inch, insert foam backer rod into the gap before applying the caulk. The caulk bead will have its strongest bond when tooled into an hourglass shape over the backer rod.

#3 - Install Rigid Aluminum Weather-stripping

Once the surrounding construction was sealed, I still had to deal with the gap between the jamb and the edges of the door, which measured up to 1/2 inch.

Hardware stores sell several types of weather-stripping, but I prefer the kind with a rigid aluminum bar lined with a soft rubber gasket, called a bulb. When attached to the jamb, the bulb compresses against the closed door to prevent the passage of air and moisture. The kits include three pieces, one for the top and two for the door sides, all of which can be trimmed to size.

Use a tape measure to find the length from the bottom of the door frame to the top of the jamb. Use a hacksaw to cut the aluminum and a utility knife to cut the rubber gasket. When cutting, err on the side of too long and adjust as necessary.

Position the strip against the closed door. Close the door and press the weather-stripping firmly against it. Insert the screws that came with the kit through the holes in the strip and start driving them into the door frame. Don’t tighten them all the way down at this time. Leave them proud so the weather-stripping remains loose until all the screws have been started.

(Note: If installing in a metal door frame, first mark the screw holes in the weather-stripping with a pencil. Metal door frames will require pilot holes to be drilled for the screws with a 1/16-in. spiral tip bit.)

Measure, cut and fasten the second strip onto the opposite side of the jamb. With the side strips in place, measure between them to find the length of the top piece, then cut to fit and install the same way.

Once the three strips are in place, latch the door closed and position the strips so the bulbs are compressed against the door surface. Close the door a few times to check the seal and make minor adjustments. The oblong screw slots enable you to back out the fasteners, move the strip as necessary and then re-tighten until you’ve completely closed off the gap. (Don’t compress the bulb more than 50 percent or you could damage the gasket.)

When you’re satisfied with placement, use a screwdriver to tighten the screws by hand to complete the job. A powered driver risks over-driving the screws, which could deform the metal strip.

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