Draft Under the Door? Find the Gap, Then Fix It Cheaply
Most door drafts are a threshold set too low, a worn sweep or a latch that never pulls the door tight. Find the gap first and the fix usually costs very little.
A draft under the door comes from one of four places: the gap over the threshold, a worn door sweep, the latch side where the door never pulls tight, or the hinge side of a door that has sagged. Each has a different fix, and the cheapest ones cost nothing. Find which gap is leaking before you buy anything, because a new sweep does nothing for a door that is not closing against its seal.
Key takeaways
- Look for daylight around the closed door with the room dark. A line of light along the bottom means the threshold or sweep is not touching.
- Many exterior thresholds have adjustment screws. Turning them raises the strip to meet the door, for free.
- A sheet of paper closed in the door shows where the weatherstripping is not compressed.
- A latch that catches too early leaves a gap down the whole side. Moving the strike plate pulls the door tight.
- If you rent, a draft snake and stick-on seals block most of it and come away without damage.
Why doors leak in the first place
A door has to move, so it cannot be sealed shut like a window frame. The US Department of Energy's air-sealing guidance separates the two: caulk for gaps that never move, weatherstripping for parts that open and close. Weatherstripping only seals when it is pressed. A strip that the door never touches, or one worn flat after years of use, leaves the gap open.
The bottom of an exterior door is sealed by two parts meeting: the threshold on the floor and a sweep or rubber bottom on the door. If either sits too low, or the rubber has hardened and split, there is a gap the full width of the door. The sides and top are sealed by the strip in the frame, and that only works if the latch holds the door firmly against it.
Find the gap before you fix anything
Do these on a cold or windy day, when the pressure difference makes leaks easy to find.
- The daylight check. Turn off the lights in the room on a sunny day, close nearby curtains, and look around the closed door, lying on the floor for the bottom edge. Family Handyman notes that a sliver of light at the two bottom corners is normal on many doors. A line of light along the threshold is not.
- The paper check. Close the door on a sheet of paper at several points: along the bottom, up the latch side, up the hinge side and across the top. Where it slides out with no resistance, the seal is not compressed.
- The hand check. On a windy day, move the back of a damp hand slowly around the edges. You will feel a cold line where air is coming through.
Note where each leak is. Most doors leak in one or two places, not all four.
How to stop a draft under the door, gap by gap
| Where the draft is | What you see | Fix | Cost | Renter-safe |
|---|---|---|---|---|
| Along the bottom, exterior door | Light along the threshold | Raise an adjustable threshold | Free | Usually, it is an adjustment |
| Along the bottom, any door | Light under a door with no seal | Fit a door sweep | Low | Stick-on sweeps, yes |
| Latch side | Paper slides out by the lock | Move or adjust the strike plate | Free to low | Ask the landlord first |
| Hinge side or top | Light at the hinge side, door rubs | Tighten hinge screws, then replace worn strips | Free to low | Tightening screws, yes |
Raise an adjustable threshold
Many exterior doors have a threshold with a row of large screws along its top. Family Handyman's guide sets out the method:
- Find the screws nearest the light you saw.
- Turn them anticlockwise a little at a time. That lifts the strip.
- Lay a straight edge along the strip so it stays level across the door.
- Close the door and check again. Repeat until the light is gone.
Stop once the light disappears. Raised too far, the strip presses hard on the door's bottom seal, the door drags, and the rubber wears out fast.
Fit a door sweep
Where the threshold is fixed, or the door is an interior one with no seal at all, a sweep closes the gap. Measure the door's width, cut the sweep to length, and fix it to the inside face at the bottom. Set it so it just touches the floor or threshold when the door is shut. Set too low, it makes the door hard to open and the rubber wears quickly.
Screw-on sweeps last longest. Self-adhesive ones are quicker, leave the door undamaged when removed, and suit a rental or an interior door.
Pull the door tight at the latch
If the paper slides out along the latch side, the latch is catching before the door reaches its weatherstripping. Start with the screws holding the metal strike plate in the frame. Loose screws let it shift. If a screw just spins, Home Depot's guide suggests gluing a wooden golf tee into the hole, trimming it flush and driving the screw back in.
If the plate is tight and the door still closes loose, the strike needs to sit slightly further toward the weatherstripping, so the door has to close further before the latch catches. That means moving the plate a few millimetres and enlarging its recess with a chisel. Adjustable strike plates do the same job with a screw. On a rented home, ask before you cut the frame.
Fix the hinge side
Light along the hinge side, or a door that rubs at the top corner on the latch side, usually means the door has dropped. Tighten every hinge screw first. It is the same check as when a door starts squeaking, and a loose top hinge causes both. If the weatherstripping in the frame is flattened, split or missing, replace it. Pull a short piece out and take it to the shop to match the profile.
Mistakes that leave the draft in place
- Fitting a sweep to a door that does not close tight. The bottom seals and air keeps coming in down the side. Do the paper check first.
- Setting the sweep or threshold too high. The door drags, someone forces it, and the seal tears within weeks.
- Caulking the gap the door moves through. It cracks the first time the door opens and stops the door closing properly.
- Buying new weatherstripping before tightening the hinges. A sagging door will not meet new strips any better than old ones.
If you rent
A fabric draft snake along the bottom of the door is the quickest fix and goes with you when you move. Self-adhesive sweeps and foam strips come off with care. Tightening loose hinge or strike screws is ordinary upkeep. Raising a threshold is an adjustment rather than an alteration, but moving a strike plate means cutting the frame, so ask first. Report a door that will not close properly early in the season, along with any drafty windows. It is usually the landlord's to fix.
A door that seals properly is one of the cheapest items in lowering your heating bill without being cold. Start with the threshold screws, because they cost nothing and fix the most common leak.
Frequently asked questions
How do I stop a draft under my door without a door sweep?
On an exterior door, check for an adjustable threshold first. Many have large screws along the top that raise a strip to meet the door, and that costs nothing. If you rent or cannot screw anything to the door, a fabric draft snake laid against the bottom works on any door and lifts away when you leave.
Why is there a draft at the side of my door when it is closed?
The latch is probably catching before the door presses into its weatherstripping. Close the door on a sheet of paper at the latch side. If the paper pulls out easily, the seal is not compressed there. Moving the strike plate toward the weatherstripping, or tightening loose hinge screws, usually closes it.
How much light under a door is normal?
On a sunny day with the room dark, a sliver of daylight at the two bottom corners is normal on many exterior doors. A line of light along the threshold is not. That means the bottom seal is not touching, and the threshold or the sweep needs adjusting.
Should I caulk around my door to stop drafts?
Caulk the gaps around the fixed frame, where trim meets wall, but never the gap the door itself moves through. The US Department of Energy's guidance is that moving parts like doors and opening windows are sealed with weatherstripping, which compresses when they close and lets them open again.
