How to Stop Cold Air Coming In Under Your Front Door

To stop cold air coming in under a front door, find out which of three things has failed: the door sweep on the bottom of the door, the threshold it closes against, or the door itself, which may have dropped on its hinges. In most Metro Detroit homes the fix is to raise an adjustable threshold a quarter turn at a time or to replace a worn sweep, and both are afternoon jobs. If the gap is wider at one end than the other, or the wood under the door is soft, a new seal will not hold and the frame needs attention first. October is the month to check: the first freeze usually reaches Wayne, Oakland and Macomb counties in the second half of the month, and DTE Gas base rates went up in mid-September after a Michigan Public Service Commission order dated September 10, 2026, so heat lost under a door costs more this winter than it did last winter.

Find exactly where the air is getting in

Do not buy anything until you know where the leak is. A draft you feel at your ankles can come from under the door, from the two bottom corners, or from the latch side of the frame, and each has a different fix.

Wait for a windy evening and run the back of your hand slowly along the bottom of the closed door, then up both sides. A stick of incense or a strip of tissue held near the gap shows the same thing more clearly. After dark, have someone shine a flashlight along the bottom of the door from outside while you look from inside with the hall light off. Any line of light is a line of cold air.

Then do the paper test. Open the door, lay a strip of paper across the threshold, and close the door on it. If the paper slides out with no drag, the sweep is not touching the threshold at that spot. Repeat it at the hinge side, the middle and the latch side. Drag at one end and none at the other tells you the gap is wedge shaped, which matters later.

• Light or air along the whole bottom edge: sweep worn out or threshold set too low
• Light only at the two bottom corners: the corner pads are missing or crushed
• Tight at one end, open at the other: the door has dropped or the frame is out of square
• Soft, dark or crumbling wood at the sill: water damage, not a sealing problem

Raise the adjustable threshold first

Most steel and fiberglass entry doors fitted in the last thirty years close against an adjustable threshold. Look for a wood or composite strip running along the top of the sill with three or four round plugs or screw heads in it. Those screws raise and lower the strip.

Pop the plugs if there are any, and turn each screw counterclockwise a quarter turn to lift the strip. Work along all the screws evenly, close the door, and repeat the paper test. Stop when the paper pulls out with light, even drag along the full width.

Do not overdo it. A threshold set too high makes the door hard to latch, grinds the sweep away in one winter, and can leave the deadbolt out of line with its strike. If the screws are stripped, rusted solid or the strip is cracked, the threshold cap needs replacing, not adjusting.

Replace a worn door sweep

If the threshold is already as high as it will go, or the rubber fins on the bottom of the door are torn, flattened or hard, the sweep is finished. Road salt, grit and a few Michigan winters are enough to do it. Sweeps come in three main kinds, and you need the one that matches your door.

Take the old one to the store with you, or a clear photo of the door bottom and the door width. A kerf sweep usually means lifting the door off its hinges, which is a two-person job with a heavy entry door. Cut the new sweep to length, fit it, rehang the door, and reset the threshold so the fins just compress.

Older houses in Detroit, Dearborn and Royal Oak often have something different: an aluminum saddle threshold with a vinyl bulb down the middle, and a plain wood door above it. The vinyl insert pulls out and a new one presses in. If the aluminum is bent or the insert size is no longer sold, the threshold itself is due for replacement.

• Kerf sweep: pushes into two slots cut in the bottom of a steel or fiberglass door
• Wrap-around sweep: a U-shaped channel that slides over the door bottom and screws to the inside face
• Surface strip: screws to the inside face of a wood door and brushes the threshold
• Vinyl bulb insert: sits in the threshold, not on the door, on many older wood doors

Check the corners and the hinges

The two bottom corners are where a sweep and the side weatherstripping meet, and they rarely meet perfectly. Factory doors have a small foam wedge, called a corner pad, stuck to the jamb at each bottom corner to plug that spot. They get kicked off, painted over or crushed flat. New ones are self-adhesive and take a minute to fit.

If the paper test was tight at one end and loose at the other, look at the hinges before the seals. Open the door and lift gently on the handle. Movement at the top hinge means loose screws. Tighten them, and if they spin without gripping, replace one screw in the top hinge on the jamb side with a three-inch screw that reaches the framing behind the jamb. That often pulls a dropped door back up and closes the gap on its own.

A storm door in front of the entry door adds a second layer of still air in winter and takes the wind off the main seals. It does not fix a failed sweep, but it makes a sound one work better. Our storm door installation page covers what suits a Michigan entry.

When a new seal will not fix it

Some drafts are not sealing problems. Freeze-thaw cycles, snowmelt and wind-driven rain work on the bottom of a door frame for years, and what they leave behind cannot be solved with rubber.

A wedge-shaped gap that stays after the hinges are tight means the frame has moved out of square. A sweep can only bridge an even gap, so new weatherstripping helps a little and then fails again. Soft or stained wood at the sill or the bottom of the jambs means water has been getting in, and the rot will keep travelling. A door that has warped so one corner stands off the stop will leak whatever you fit to it.

In those cases the order matters: make the frame sound and square, then seal it. That is door frame repair, and it is usually a smaller job than people expect when it is caught before winter. A door that sticks, sags or will not latch as well as letting in air is a door repair visit. Our guide to whether to repair or replace a door frame explains how we decide.

• The gap is wider at one end even with the hinges tight
• Wood at the sill or jamb bottoms is soft, dark or flaking
• Daylight still shows at a corner after new pads and a new sweep
• The door rubs at the top and gaps at the bottom, or the deadbolt no longer lines up
• The threshold rocks, is cracked, or water stains the floor inside after rain

Get it done before the first hard freeze

Rubber and vinyl stiffen in the cold, adhesive pads do not bond well below about 40 degrees, and nobody wants a front door off its hinges in January. A frost advisory was already issued north of I-69 on October 6, so the window for an easy fix in Metro Detroit is the next couple of weeks.

What a repair costs depends on what the paper test finds: a sweep or a threshold cap is a short visit, a frame that has to be squared or a rotted sill is more work, and the door material and the age of the house both change the parts involved. We do not publish prices on this site because every opening is different. Call (313) 236-4558 for a price on your job.

We fix drafty, sagging and sticking doors across Wayne, Oakland and Macomb counties, including Detroit, Royal Oak, Troy, Warren, Dearborn and Southfield. Call (313) 236-4558, Sunday to Thursday 9am to 5pm and Friday 9am to noon, or contact us and we will call you back.