Unfortunately, a door's weather seals, if it has any at all, can rip, compress, bend, or wear out over time, leaving chilly winter air free to enter (or expensive air-conditioned air to leave). Fortunately, attaching new weather seals is a straightforward exercise, far cheaper and faster than installing a new door.
It costs approximately $100 for materials and labor to seal a door. And when you consider that even a tiny 1/8-inch gap around a typical entryway door is the equivalent of drilling a 5 ½-inch-diameter hole through an outside wall, closing that gap is well worth the effort.
How Do You Seal a Gap in a Door?
Any well-sealed door requires two components: weatherstripping, which covers the sides and top of the door, and a sweep, which fills the space between the threshold and the door bottom. Hardware stores and home centers sell an array of metal, foam, felt, and plastic products for this purpose.
Tom prefers a weather seal system that includes a tubular silicone weatherstripping that fits against the doorstop and a twin-fin silicone sweep that fits beneath the door. Silicone makes an ideal weatherstripping because it's durable, soft, and has no "compression memory"; it remains tight as the door swells and shrinks. The following steps will teach you how to weatherstrip a door to keep cold drafts from entering your home.
Ian Warpole
Before ordering weatherstripping, measure the gap between the door and jamb and the door and stop with the door closed. Make sure to take measurements along both side jambs and the head jamb, then choose weatherstripping for each side that's big enough to fill the largest gap along its run (3/8-inch maximum).
Step 2: Cut a groove
Kindra Clineff
Pull a paint scraper along the stop and jamb to make sure that both surfaces are smooth, flat, and free of protruding nails. Fit the grooving tool's V-shaped base into the corner formed by the jamb and the stop, with the bit pointing up.
Turn on the motor and push the tool up to the head jamb. This creates a slot 1/8 inch wide and 3/16 inch deep. At the top, turn off the motor and remove the bit from the slot. Reinsert it at the starting point, but this time with the bit pointing down. (Retracing your path in the slot can widen it too much to grip the weatherstripping.)
A steady push to the bottom of the jamb with the motor revving finishes the slot on that side. Repeat the process on the opposite side jamb and the head jamb. If the shop vacuum leaves any wood chips in the slot, Tom gently cleans them out with a small screwdriver before he continues to weatherstrip the door.
Step 3: Insert the weatherstripping
Kindra Clineff
Tom takes one end of the weatherstripping and pushes its barbed tongue into one end of the slot. As he works up the slot, he's careful not to stretch the weatherstripping; it will return to its original length and leave gaps.
A couple of inches from the slot's opposite end, he gauges the proper length and cuts the strip with scissors. (Another method eliminates the possibility of stretching: Cut the product to length first, fit its ends into the ends of the slot, then push in the barb at the halfway point. Continue to push at each of the quarter points, and so on until the entire strip is secure.)
It's not necessary to miter the ends where they meet at the head jamb; a butt joint seals best. To finish, drive the weatherstripping into its slot with a spline roller. Check the installation by shutting the door from the outside and looking for gaps.
Step 4: Rout the dado
Kindra Clineff
To seal the door gap in the bottom, place the door on sawhorses and use a square to mark out a 5/8-inch-wide dado centered on the door's bottom edge. Tom sets the router's guide so a ½-inch bit will cut next to the top mark when the guide rests on the door's top face. On the first pass, move the router from left to right. On the second pass, the guide rides on the door's opposite side as the router moves from right to left. Make multiple passes to reach full depth (1⅛ inch).
Step 5: Attach the channel
Kindra Clineff
Coat the exposed wood in the dado with primer and paint. Then cut the sweep's two aluminum channels just 1/8-inch shy of the width of the door (to allow for end caps to be installed later). To make sure the cut is clean, Tom clamps the channels in a miter box and uses a hacksaw with a waxed blade. Insert one channel into the dado, center it end to end, and screw it in place, as shown.
Kindra Clineff
After he fits the black silicone sweep into the free channel, Tom slides the glides into the channel in the dado, then carefully rehangs the door. (To avoid the possibility of damage to the sweep, hang the door first, then install the sweep.)
Adjust the glides until no light shows between the sweep and the threshold when the door is closed. To seal the ends of the dado, snap plastic caps into the ends of the channel and stick squares of adhesive-backed pile against the bottom of the jambs.
Step 7: Adjust the glides
Ian Warpole
The secret behind this sweep's adjustability is its glides, which lift or lower the sweep by as much as ¼ inch. To adjust the fit, simply open the door, remove the end cap from the latch side, and slide out the sweep. Turning the glides clockwise raises the sweep; counter-clockwise lowers it. Then slide the glides back into the attached channel.
A gap under a front door results in higher heating and cooling costs, as the air you're paying to heat or cool escapes beneath the door while the outdoor air seeps in. A gap also provides a convenient access point for insects or rodents. Thankfully, a door gap is easily remedied by adding a door sweep, which can be found at a home improvement store. These sweeps are available with many options and in numerous sizes; some even have a peel-and-stick backing for simple installation.
Slide-On and Stick-On Door Sweeps
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Slide-on and stick-on door sweeps require no tools for installation, but you may need to cut the sweep to length (using a hacksaw) if it's too long for the door. Measure the width of the door, or both the width and thickness for a slide-on model to determine which size sweep to buy. The stick-on type installs by peeling off the backing, then sticking the adhesive along the bottom of the door. Sweeps install on the side of the door that is pulled, not pushed. A slide-on sweep has a channel that slides onto the bottom of an open door.
Screw-Based Models
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Many sweeps include screws and have pre-drilled screw holes for installation. Line this type up along the bottom of the door so it just touches the threshold, then mark through the screw holes in the sweep. Once pilot holes have been drilled on the marks, install the sweep, adjusting its height as needed with the screws loosely in place.
By Dale Yalanovsky Updated December 27, 2018
Door gaps, especially on exterior doors, can be serious energy wasters. In the winter they let cooler air in, and in the cooling season when your air conditioner is running, they let cool air out. If you have individual heating and cooling for each room, the same situation applies for interior doors too. However, unless you want to raise the entire floor beneath the door, there are ways to close the gap that are do-it-yourself methods and are cost-effective.
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Screw on a door sweep. This is done from inside the home on an exterior door, and the sweep will effectively block the gap under the door. There are several types available, from an actual bristle-type sweep that hangs below the door and blocks the gap, to rubberized types that bulge slightly to fill the gap.
Measure the width of the door and transfer that measurement onto a door sweep with a marker. Put on a pair of safety glasses and cut the sweep to length with either a hacksaw or a jigsaw. Place the sweep at the bottom of the door and align the sweep edge so that it blocks the door gap. Make marks through the pre-drilled attachment holes onto the door proper. Pilot hole the marks with a drill and drill bit, then insert a screwdriver bit into the drill and screw the sweep down through the drilled holes. All sweeps will come with mounting screws for ease of application.
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Add-on a slide-on or wrap-around type of door sweep. These are the easiest types to install and they either slide onto the bottom of the door or flex so that they wrap around the door bottom edge. Although you won't have to remove the door to do this, it will need to remain open during installation.
Measure the width of the door and transfer the measurement to the slide-on door sweep. Put on a pair of safety glasses and cut the sweep to the measured length using either a hacksaw or a jigsaw. Open the door fully and slide on the door sweep at the bottom of the door. If you have a large gap beneath the door, use a wrap-around door sweep. They have long adjustable sides that can be moved up and down along the width of the door. When the bottom of the sweep fills in the door gap, drill pilot holes through the sides and screw it down.
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Put in a door threshold. These gap sealers mount directly to the floor and have a rubberized gasket that protrudes upward that comes into contact with the bottom of the door. They are the most labor-intensive but they blend in nicely and don't look like they have been added on.
Measure the distance between the door frames at the floor. Transfer this measurement to the threshold, put on a pair of safety glasses, and cut it to this length with a hacksaw or jigsaw. Place the threshold onto the floor between the frame members and drill pilot holes for the mounting screws. Mounting holes in the threshold will have been pre-drilled at the factory to facilitate this action. Turn in the mounting screws and tighten them securely. Slide or push in the gasket into the channels on the threshold to effectively seal the gap beneath the door.
Things You Will Need
Door sweep
Tape measure
Marker
Safety glasses
Hacksaw or jigsaw
Drill with drill bit
Screwdriver drill bit
Slide-on door sweep
Threshold
If you have an old threshold that you are going to replace, unscrew it from the floor, pry it up, gently, with a screwdriver or pry bar, and use that as a template for the correct measurement on the new threshold.