01 / DOORS
How to stop a draft coming under a door
Measure the gap, pick the part that reaches it, fit it so it touches without dragging. That is the whole job, and it takes under an hour.
Measure the gap under the door at three points and take the largest. Under a quarter inch, fit a slim blade sweep. A quarter to three quarters, fit an aluminum sweep with a rubber blade. Over that or on an uneven floor, fit a brush sweep. If you cannot drill the door, use an adhesive sweep or a slide-under stopper.
A draft under a door is the easiest air leak in a house to fix, and the one people most often fix twice. The reason is always the same: the part was chosen before the gap was measured. Do these steps in order and it is a one-shot job.
Step 1: measure the gap, in three places
- 1Close the door. Kneel so your eye is at floor level on the inside.
- 2Slide a tape measure into the gap at the latch side. Note the number.
- 3Do the same in the middle of the door and again at the hinge side.
- 4Take the largest of the three — that is what your seal has to close.
- 5If the largest and smallest differ by more than about a quarter inch, your floor is not level and you need a brush sweep. This one check saves most of the failed installs in this category.
Step 2: pick the part that reaches
| Your gap | Buy this | Why |
|---|---|---|
| Under 1/4 in | Slim vinyl blade sweep | A short face is enough and it looks like trim |
| 1/4 in to 3/4 in | Aluminum sweep with a rubber blade | The standard exterior fix; rubber works cold |
| Over 3/4 in, or floor uneven | Aluminum and brush sweep | Bristles bend to a changing floor height |
| Any gap, cannot drill | Adhesive silicone sweep | Trims to the gap; needs a smooth clean door face |
| Any gap, renting, textured door | Slide-under draft stopper | Attaches to nothing. See our stopper picks |
Quick picks
Ranked for fit, not for hype. Tap a row to jump to the full write-up, or go straight to the listing.
| # | Product | Best for | Gap range | Price |
|---|---|---|---|---|
| 1 | Frost King A79/36H Premium Aluminum and Reinforced Rubber Door SweepA screw-on aluminum carrier with a reinforced rubber blade — the version of this part that survives a winter of a storm door slamming into it. | Exterior doors, screw-mounted | Roughly 1/4 in to 3/4 in | CHECK PRICE |
| 2 | Suptikes Door Draft Stopper Under Door SweepA silicone blade on a strong adhesive strip — the sweep you use when drilling the door is not an option. | Renters and no-drill installs | Roughly 1/8 in to 1 in | CHECK PRICE |
| 3 | Frost King SB36 Extra Aluminum and Brush Door SweepBristles instead of a blade, which is the difference between sealing a floor that is flat and sealing a floor that is not. | Uneven floors and carpet | Roughly 1/2 in to 1 in | CHECK PRICE |
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Exterior doors, screw-mounted
Frost King A79/36H Premium Aluminum and Reinforced Rubber Door Sweep
Published gap range
Roughly 1/4 in to 3/4 in
#ad · how we are funded · no live price right now
A screw-on aluminum carrier with a reinforced rubber blade — the version of this part that survives a winter of a storm door slamming into it.
Where the number comes fromFrost King does not publish a numeric working range for this sweep. The 2-inch face and the rubber blade's projection put it in the quarter-inch-to-three-quarter-inch band once mounted; the blade must touch the threshold under light compression, not bend flat. Measure before you buy.
- Carrier
- Aluminum
- Blade
- Reinforced rubber
- Published size
- 2" x 36"
- Mounting
- Screws (supplied)
- Maker's claim
- Lifetime guarantee on weathersealing ability
- Mounting
- Screws through the door face, above the threshold
What it does well
- Screws, not adhesive — nothing to peel off in July
- Cuts down with a hacksaw for a narrower door
- The rubber blade is replaceable in practice; the carrier is what lasts
Where it fails
- You are drilling into the door face — renters should look at an adhesive or slide-on option
- No published gap range, so measuring first is not optional
- Aluminum shows a hard line on a painted door; the finish choice matters
Who this is forAn exterior door you own, with a gap you can see daylight through and a threshold that is basically flat.
Renters and no-drill installs
Suptikes Door Draft Stopper Under Door Sweep
Published gap range
Roughly 1/8 in to 1 in
#ad · how we are funded · no live price right now
A silicone blade on a strong adhesive strip — the sweep you use when drilling the door is not an option.
Where the number comes fromThe seller publishes 2" W x 39" L and no numeric gap range. The blade is trimmed to your gap on install, which is where the flexibility comes from: too little and it drags, too much and it does nothing.
- Blade
- Silicone
- Published size
- 2" W x 39" L
- Mounting
- Adhesive, no drilling
- Trim
- Cut to door width with scissors
- Doors
- Exterior and interior
- Mounting
- Self-adhesive strip on the inside face of the door
What it does well
- No holes, so no deposit argument at move-out
- Silicone stays flexible far below freezing where cheap vinyl stiffens
- Trims to width in one cut
Where it fails
- Adhesive needs a clean, smooth, dry surface — it will not hold on a textured or freshly painted door
- A door that gets kicked open will peel it eventually
- No published gap range; you are sizing it by eye against your own gap
Who this is forRenters, and anyone who wants the draft gone tonight without a drill.
Uneven floors and carpet
Frost King SB36 Extra Aluminum and Brush Door Sweep
Published gap range
Roughly 1/2 in to 1 in
#ad · how we are funded · no live price right now
Bristles instead of a blade, which is the difference between sealing a floor that is flat and sealing a floor that is not.
Where the number comes fromFrost King publishes the 2 in x 36 in size but no numeric gap range. A brush seals by bending, so it tolerates a gap that changes across the door swing — which is exactly the case a rubber blade fails at. Set it so the bristle tips just brush the floor.
- Carrier
- Aluminum
- Seal
- Nylon brush
- Published size
- 2" x 36"
- Mounting
- Screws
- Slotted holes
- Height adjustable after mounting
- Mounting
- Screws through the door face
What it does well
- Brush deals with a floor that rises across the swing; a blade cannot
- Sweeps over carpet and tile transitions without dragging
- Slotted mounting holes let you drop it a few millimeters after the first test
Where it fails
- A brush leaks more air than a compressed rubber blade on a flat threshold
- Bristles flatten with heavy traffic over a few seasons
- Not the pick if you are chasing a fully airtight seal on a flat sill
Who this is forA door that scrapes on one side and swings free on the other, or one that opens onto carpet.
Step 3: fit it so it touches, not drags
- 1Clean the bottom of the door face. Old adhesive residue is the number one reason a new sweep fails.
- 2Hold the sweep up against the closed door and mark where the blade just touches the floor under light pressure — not squashed flat.
- 3Cut to width. Hacksaw for an aluminum carrier, scissors for an adhesive strip. File the cut end so it does not catch.
- 4Fix the top screw only, close the door, and feel the drag. Adjust in the slotted holes before driving the rest.
- 5Open and close ten times. If it drags, drop it an eighth of an inch. If daylight shows at one end, you have an uneven floor and a brush sweep is the right part.
If it still feels drafty afterwards
The bottom of the door is usually the most obvious leak and rarely the biggest. Once it is sealed, run the back of your hand slowly down the latch side of the frame, then across the top. If you feel air there, the frame needs weather stripping — which is a separate part and a separate twenty minutes.
And if the whole room still feels cold, the door may not be your main leak at all. How to find drafts in your house walks through the tests that find the ones you cannot feel.
How we picked
- Every recommendation on this page is placed by the gap it can physically close, using the manufacturer's own published dimensions.
- Where a maker publishes no working range, we say so rather than inventing one.
We have not tested these products and we do not claim to have. The full method, including what we refuse to claim, is on how we pick.
Questions people actually ask
- How do I stop a draft under my front door without drilling?
- Fit an adhesive silicone sweep to the inside face of the door, or slide a draft stopper under it. The adhesive version seals better but needs a smooth, clean, fully cured door face to hold.
- How big a gap under a door is normal?
- Around half an inch is common on an interior door, allowing for flooring. On an exterior door the gap should be small enough that the sweep or bottom seal touches the threshold — if you can see daylight along the whole width, something is missing or worn.
- Will a rolled-up towel work?
- For one evening, yes. It also gets kicked aside every time the door opens, and against an exterior door it will get damp and stay damp. A ten-dollar sweep is the actual fix.
- Should the door sweep touch the floor?
- It should just touch under light pressure. A blade compressed hard against the floor drags, wears out fast and eventually stops the door latching. Fit it, test it, then drop it an eighth of an inch if it drags.
Sources
Every specification on this page traces to a published manufacturer or retailer listing. Where a maker publishes no working gap range, we say so rather than estimating one.
Read next
The best door sweeps, sorted by the gap they actually close
Six sweeps placed by the gap they close, from a slim vinyl blade to a brush for uneven floors.
How to measure a door gap properly
The index-card method, the three-point rule, and how to read your number against a published seal size.
The best door draft stoppers when you cannot drill the door
No-drill stoppers ranked by published fit, including the one that states an actual gap range.