01 / DOORS
How to stop a draft from a pet door
A pet flap is a hole in an exterior door with a rubber curtain over it. There are two separate leaks and they need different fixes.
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A pet door leaks two ways: around the frame where it was cut into the door, and through the flap itself. Test them separately with a lit incense stick. Frame leaks are sealed with weather stripping or caulk from the inside; flap leaks are fixed by adding a second flap, weighting the existing one, or fitting a magnetic strip.
It is worth being honest about the ceiling here. A pet door is a deliberate hole in the building envelope with a flexible cover, and it will never seal like a solid door panel. What you can do is close the frame gap completely and cut the flap leakage substantially, and between them that usually removes the cold spot people notice.
Separate the two leaks in two minutes
- 1Light an incense stick or a match and blow it out so it smokes.
- 2Hold the smoke slowly around the outside edge of the pet door frame, where it meets the door panel. Watch for the smoke pulling sideways.
- 3Now hold it at the bottom edge of the flap, then the sides of the flap.
- 4Note which one moves the smoke. Usually it is both, and the frame is worse than people assume.
Fix 1: the frame gap
When a pet door is installed, a hole is cut through the door and the frame is screwed on from both sides. If the cut was rough or the door has flexed since, air moves straight through the gap between the frame and the panel — and this path is completely unobstructed, unlike the flap.
- Take the interior frame off if you can. It is usually four screws.
- Run a bead of thin foam tape or a V-strip around the cut edge so the frame compresses onto it when you refit.
- If you cannot remove the frame, run a fine bead of removable rope caulk in the joint from the inside. It is reversible and invisible from a normal viewing distance.
- Check the screws. Half the frame leaks in pet doors are just loose fasteners letting the two halves separate.
Fix 2: the flap
A single vinyl flap hanging on a hinge seals under its own weight and nothing else. Three things improve it, in increasing order of effort:
- 1Clean the flap and the frame's contact strip. Grit and hair on the sealing edge holds the flap open by a millimeter along its whole width, which is a bigger hole than it sounds.
- 2Check or add the magnetic strip. Most pet doors have a magnet at the bottom of the flap and a steel strip in the frame. If the magnet is weak or the strip has been painted over, the flap floats. Replacement magnetic strip is cheap.
- 3Add a second flap. A dead air gap between two flaps does far more than one heavier flap, for the same reason double glazing works. Some frames take a second flap directly; otherwise a strip of clear vinyl fixed above the opening on the inside acts as an inner curtain. If the frame takes neither, the replacement doors built around two or three flaps are in best insulated dog doors.
The rest of the door
A pet door sits in the lower panel of a door that is often old and often drafty in its own right. Once the flap and frame are dealt with, do the bottom and the sides: best door sweeps for the gap underneath and weather stripping for the frame. On most houses those two are larger leaks than the pet door ever was.
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 |  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 | $8.98 · CHECK ON AMAZON |
| 2 |  fowong Open Cell Foam Weather Stripping, 1 in x 1/2 in x 13 ftHalf-inch-thick open-cell foam for the gap nothing else reaches — an AC surround, a loose sash, a warped frame. | Large, irregular gaps | Published 1/2 in thick; fills gaps of roughly 1/8 in to 3/8 in | $16.99 · CHECK ON AMAZON |
| 3 |  M-D Building Products V-Flex Window Seal Weatherseal, 3/8 in x 17 ft, WhiteV-strip folds into the gap and springs back, so it seals a jamb that never closes to exactly the same place twice. | Door and window frame sides | Published 3/8 in wide x 17 ft; M-D publishes no gap range | $8.62 · CHECK ON AMAZON |
#ad · how we are funded · price as of October 17, 2026
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 · price as of October 17, 2026
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.
Large, irregular gaps
fowong Open Cell Foam Weather Stripping, 1 in x 1/2 in x 13 ft
Published gap range
Published 1/2 in thick; fills gaps of roughly 1/8 in to 3/8 in
#ad · how we are funded · price as of October 17, 2026
Half-inch-thick open-cell foam for the gap nothing else reaches — an AC surround, a loose sash, a warped frame.
Where the number comes fromfowong publishes 1" wide x 1/2" thick x 13 ft. Open-cell foam compresses much further than rubber, which is why it covers a wider range — and also why it is not a long-life exterior seal.
- Material
- PU foam, PE cover
- Published width
- 1 in
- Published thickness
- 1/2 in
- Published length
- 13 ft
- Mounting
- Strong adhesive
- Mounting
- Self-adhesive
What it does well
- Half an inch of squash covers gaps rubber sections cannot
- The PE facing sheds water better than bare foam
- Cheap enough to over-buy and cut down
Where it fails
- Open-cell foam holds water if the facing is cut or torn
- Shortest life of any seal here in direct weather
- Too thick for a door that latches tightly
Who this is forA portable-AC surround, a basement sash, or any gap you can push a finger into.
Door and window frame sides
M-D Building Products V-Flex Window Seal Weatherseal, 3/8 in x 17 ft, White
Published gap range
Published 3/8 in wide x 17 ft; M-D publishes no gap range
#ad · how we are funded · price as of October 17, 2026
V-strip folds into the gap and springs back, so it seals a jamb that never closes to exactly the same place twice.
Where the number comes fromM-D publishes the strip width (3/8 in) and the roll length (17 ft), not a gap range. Our reasoning, stated as reasoning: a V-strip is folded along its crease and stands off roughly half its flat width, so a 3/8 in strip suits a hairline gap up to somewhere around 1/8 in. Past that it stops making contact and you want a bulb or D-section instead.
- Profile
- V (tension) strip
- Published width
- 3/8 in
- Published length
- 17 ft
- Mounting
- Self-adhesive
- Color
- White
- Mounting
- Self-adhesive, folded along the crease onto the jamb
What it does well
- Springs back after every close, so it keeps sealing as the door settles
- Nearly invisible once the door is shut
- A named manufacturer that publishes the width, which most V-strip listings do not
Where it fails
- 17 ft only just covers one standard door frame, so there is very little margin for a mis-cut
- Narrower than the 1/2 in strips, so it reaches a smaller gap
- Adhesive fails on rough, dusty or freshly painted wood
Who this is forThe sides and top of a door or a double-hung window, where the gap is thin and uneven.
How we picked
- The two leak paths are separated first, because they need different parts.
- Products are placed by published section against the gap at each point.
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 cold air coming through my pet door?
- Test the frame and the flap separately with incense smoke. Seal the frame-to-door joint with thin foam tape or rope caulk, then clean the flap's sealing edge and check the magnetic strip. Adding a second flap creates a dead air gap and does more than any single upgrade.
- Do draft-proof pet doors work better?
- Dual-flap models genuinely seal better than single-flap ones, because the air gap between the flaps does the work. Whether the upgrade is worth it depends on how much of your leak is the flap versus the frame — test first.
- Can I use weather stripping around a pet door?
- Yes, on the joint between the pet door frame and the door panel. Use a thin foam or V-strip so the frame still pulls up tight when you refit the screws. Do not put weather stripping on the flap's sealing edge, where it will hold the flap open.
- Should I remove the pet door in winter?
- Only if the pet no longer uses it. Refitting a pet door properly is more work than sealing it, and a badly patched hole in an exterior door leaks more than the pet door did. Use the maker's locking cover panel instead.
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
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