A door can be solid, well hung, and still leak like a screen. The seal around it is a wear item: foam flattens, rubber cracks, and corners that were never sealed leak year after year. Most doors take under an hour and under $30 in material to reseal, and you can feel the difference the same evening.
Close the door on a dollar bill so half of it sticks out, then pull gently. A good seal grips — you feel steady drag. A tired seal lets the bill slip free with almost no pull. Test the top corners, both sides, and the bottom, and mark weak spots with painter's tape. One weak corner often means a missing corner seal; a loose slide down a whole side means that strip has flattened.
| Type | How it fits | Typical cost | How long it lasts | Best for |
|---|---|---|---|---|
| Kerf (slot-in) | Barbed fin presses into a thin groove in the frame | $10–$25 per door | 5–10 years | Most modern prehung doors |
| Adhesive foam tape | Peel-and-stick foam on the door stop | $5–$15 per door | 1–3 years | Renters and doors with no groove |
| V-strip (tension seal) | Folded V that springs open against the door edge | $8–$20 per door | 5+ years | Uneven gaps and older doors |
| Door sweep | Screws to the bottom of the door and seals the threshold | $10–$30 | 5–10 years | The bottom gap, which frame strips do not cover |
Look for the kerf groove before you buy. A thin slot in the frame means the kerf type, the neatest and longest-lasting frame option. No slot means adhesive foam or V-strip. Take a piece of the old strip to the store — matching the profile by eye beats guessing from a package photo. Doors are one stop on a whole-house leak hunt; the same logic applies at windows and hatches, as laid out in our guide to finding and sealing air leaks in your home.
Kerf type: grip one end and pull firmly — the barbed fin walks out of the groove. A flat screwdriver under the first inch helps start it. Go slowly at corners, where the fin can tear and leave a stub in the slot.
Adhesive and V-strip types: peel the strip off, or pull its small nails with pliers, then clear sticky residue with rubbing alcohol on a rag. New tape stuck over old glue fails within a season, so this cleaning step is the job, not a nicety.
Measure and cut the top piece. Measure across the head of the frame and cut the strip about 1/8 inch long — you will trim the final fit at the corners in step 5. For kerf strip, press the fin into the groove with your thumb, working from one corner to the other. A wallpaper seam roller or the handle of a screwdriver helps seat it fully.
Do the latch side next, then the hinge side. Press each side strip in so it just touches the door face along its whole length. Too loose leaks; too tight makes the door hard to latch and crushes the seal flat within months. Stick adhesive foam to the door stop — the narrow strip the door closes against — not the frame face.
Fit the bottom. If daylight shows under the door, add or replace the sweep. Close the door, hold the sweep so its flexible edge lightly brushes the threshold along the full width, mark the screw holes, and cut it to length with a hacksaw if needed. It should drag faintly, not scrape hard enough to fight the door.
Most kits are three straight strips, and most leaks that survive a reseal live in the corners where those strips meet. Butt joints open as the material shrinks with age, leaving a pinhole that passes a surprising amount of air. Two habits fix it. First, cut the ends of the top and side strips at matching 45-degree angles so they meet like a picture frame. Second, add foam corner pads — small self-stick pads sold for this spot — at the bottom corners, where the frame strips end and the sweep begins. Retest each corner with the bill; corners should grip like everywhere else. The same gap shows up on windows, which is why our drafty window fixes start with finding the leak before buying material.
Repeat the dollar-bill test at every marked spot, plus each corner. Then check at night from outside with the hall light on: thin lines of light show any gap the bill test missed. A door that latches with a normal pull, grips the bill on all four sides, and shows no light lines is done. Expect the new seal to feel slightly firm for the first week before it takes a light set to the door.
Look at the seal on the frame. In a thin groove: kerf type. A spongy strip glued to the door stop: adhesive foam. A folded strip that springs back in the frame channel: V-strip. Take a piece of the old one to the store to match it.
Adhesive foam lasts roughly 1–3 years. Kerf, V-strip, and sweeps commonly last 5–10 years. Sun and slamming shorten those ranges. Run the dollar-bill test each fall to tell when a strip is done.
Check the corners first — unsealed butt joints are the usual leftover leak — then the bottom gap and the threshold. If the door is warped or the latch no longer pulls it tight to the stop, adjust the latch plate so the door closes snugly; no seal can compensate for a loose latch.
Yes, for kerf and V-strip, which do not rely on glue. Adhesive foam needs a clean surface above about 50°F for the backing to bond well, so warm the frame with a hair dryer first or wait for a milder day. The job itself is easier to test in winter, when drafts announce themselves.
Material for one exterior door usually runs $10–$30, depending on type, plus $10–$30 if the sweep needs replacing too. A handyperson will typically charge $75–$150 per door, parts and labor. Most doors take a first-timer under an hour.