Weatherstripping

How to Replace Weatherstripping on a Door

Replacing weatherstripping is one of the few door repairs a handy homeowner can do well. The trick is matching the right profile and getting even compression all the way around — a gap at one corner undoes the rest.

Confirm the seal is the problem

Close the door on a sheet of paper and pull. If it slides out easily anywhere, the seal is not compressing there. Do this at the top, both sides, and the latch corner. If the paper grips everywhere except one spot, that spot is your leak. If it slides out everywhere, the whole run is worn — or the door is sitting loose and needs front door adjustment first.

Gather what you need

Most weatherstripping jobs need very little: a tape measure, a sharp utility knife or scissors, and a rag to clean the channel. Kerf-in bulbs press in by hand with no glue. Nail-on strips want a hammer and small finish nails; adhesive-backed strips need a clean, dry, room-temperature surface to stick, which is one reason this is a job for a mild day rather than a deep freeze. If you are doing the door sweep at the same time, add a screwdriver and possibly a hacksaw to trim it to width. Buy a little more length than you measure so you have room to cut the corners square.

Pick the right type

The common profiles are V-strip, compression bulb (the kind set into a kerf slot on newer steel and fibreglass doors), and foam tape. For Ottawa winters, a compression bulb or a good silicone seal outlasts foam by years. If your door has a kerf slot, buy the matching kerf-in bulb — it presses in without adhesive and seats cleanly. Our guide to the best weatherstripping for Ottawa winters covers which holds up to the cold.

Measure and cut

Measure the two sides and the top of the frame and add a little for trimming. Replace the full run, not just the worn section — a patched seal almost always leaks at the joint. Cut the corners square so the strips meet without a gap. Buy a metre or so extra; trimming off a clean end is easy, but coming up short means a second trip to the store and a splice you do not want. If you are replacing a kerf-in bulb, take a short offcut of the old one with you so you match the barb size and bulb diameter — kerf profiles vary between door brands, and a bulb that is even slightly too small will not stay seated.

Install for even compression

• Pull the old strip out and clean the channel so the new one seats flat.
• Press the bulb or strip in starting at one top corner, working down each side.
• Close the door and check that it compresses the seal evenly — snug, not so tight the door is hard to latch.

Test the result the same way you tested the old seal: close the door on a sheet of paper at the top, both sides, and the latch corner. If it grips everywhere, the new seal is doing its job. If one spot still slips, that strip needs to seat a little deeper or the door needs a small alignment tweak there before the seal can bite.

While you are there, check the bottom. The sweep wears separately from the side seals; if there is daylight under the door, replace it too, and read the signs you need a new door sweep.

Do the corners right

Corners are where most DIY seals leak. Where the top strip meets the sides, the two pieces have to butt together without a gap and without overlapping so much that the door cannot close. Cut each end square, hold it in place before committing, and test-fit the door. On a kerf-in bulb, leave the corners just shy of touching so the door is not forced; on a nail-on strip, mitre or square-cut the ends so they meet cleanly. A clean corner is worth more than an expensive material, because a single millimetre gap at one corner undoes the whole run.

Pick the right time of year

In Ottawa, the best time to reseal a door is early fall, while it is still mild. Adhesive-backed strips will not bond to a cold surface, and you want the work done before the first hard frost reveals the leak the worst way — with cold air pouring across the floor in January. Doing it ahead of the season also lets you check the door's alignment in comfortable conditions, since freeze-thaw can shift a frame over the winter and reopen a gap you thought was fixed. If you are sealing in cold weather out of necessity, choose a kerf-in or nail-on profile that does not depend on adhesive.

When to call instead

If the seal is new but a draft remains, the slab is not meeting the frame evenly — that is alignment, not weatherstripping, and it is the reason a drafty front door keeps leaking after a DIY reseal. The slab may have dropped on its hinges, which is a sagging door repair, or the frame may have racked out of square and need frame repair to bring the jamb back true. We handle the seal and the alignment in one visit through our weatherstripping service, flat-rate and guaranteed across Ottawa and the Valley.