Weatherstripping is the cheapest part of a door and the one most often bought wrong. The hardware aisle offers half a dozen profiles that all claim to stop draughts, they are not interchangeable, and fitting the wrong one is why a door that was merely draughty ends up draughty and hard to close.

Start With the Gap, Not the Product

Every profile is designed for a particular gap size and a particular kind of movement. Before choosing anything, work out what you are sealing.

Close the door on a sheet of paper and pull. If it slides out with no resistance, there is a gap at that point. Doing this at several points down the latch side, the hinge side and the top tells you whether the gap is even or whether one area is doing all the leaking.

Then look at where the current seal sits: in a groove in the frame, tacked to the face of the stop, or attached to the door itself. That determines what can physically be fitted.

The Question That Decides Everything

Is the gap consistent or variable? A door that sits squarely with an even reveal can take a compression seal, which gives the best seal but needs a predictable gap. A door with an uneven reveal needs something more forgiving, because a compression seal on a variable gap either fails to touch at one end or binds at the other.

This is why so many weatherstripping jobs disappoint. The product was fine; the door was out of square, and no seal fixes geometry.

The Four Profiles, and Where Each Belongs

V-strip, also called tension seal. A folded strip that springs open against the door. It is thin, it fits in tight spaces, and it is tolerant of small variations in gap. It works well on the hinge side and the top, and on older doors with slightly irregular frames. It is not the best at sealing a large gap, and the adhesive-backed versions lose grip in cold weather. The metal versions, fastened rather than stuck, last far longer.

Compression seal, usually a bulb or Q-lon profile. A soft bulb that squashes when the door closes. This gives the best air seal of the four and is what most modern doors come with from the factory, typically sitting in a kerf groove in the frame. It needs a consistent gap, and it needs the door to latch firmly enough to compress it. On a door with a weak latch or a worn strike, a compression seal makes closing harder without sealing properly.

Magnetic seal. Works like a fridge door, pulling itself closed against a steel door or steel frame. Excellent seal, no compression force needed, so it does not fight the latch. The obvious limitation is that it needs ferrous material to grip, so it is not an option on fibreglass or wood doors, or on aluminium frames.

Brush seal. A row of dense bristles, usually used where something slides rather than swings. This is the right answer for sliding doors and for the bottom of some doors, and it tolerates uneven surfaces well. It is the weakest of the four at stopping air, so it is a poor choice for a main entrance where a bulb would fit.

Quick Matching

• Modern door, even gap, kerf groove in the frame: replace like for like with a compression bulb.
• Older door, uneven gap, flat stop: metal V-strip, fastened not stuck.
• Steel door or steel frame, want the best seal with the least closing force: magnetic.
• Sliding door, or a surface that is not flat: brush.
• Bottom of the door: a sweep or an adjustable threshold, which is a different family from all of the above.

The Mistakes That Cause Call-Outs

Adding a second layer over the old one. Two seals do not compress evenly. The door either stops latching or needs forcing, which wears the latch and the strike. Remove the old one.

Oversizing to be safe. A bulb that is too thick for the gap stops the door latching. Then the usual response is to move the strike plate to compensate, which leaves a door that latches but is permanently under tension and a seal that is crushed flat within a season.

Adhesive-backed strip on a cold or dusty surface. It needs a clean, dry, above-freezing surface to bond. Applied on a cold day to an unwashed frame, it will be hanging off by spring.

Sealing the bottom gap with side-profile product. The bottom of a door is a different problem, handled by a sweep or by the threshold, and the threshold on most modern doors is adjustable with a screwdriver before any product is needed at all. Where the door itself has been forced or damaged at the bottom rail, no sweep will seat properly until that is put right, which is damage repair rather than weatherproofing.

Treating a misaligned door as a sealing problem. If the gap is wide at the top and tight at the bottom, the door is not square in the frame and the honest fix is alignment. This is where tightening hinge screws, or a proper residential door repair, does what no weatherstripping can.

Frequently Asked Questions

How do I know which profile my door originally had?

Look at the frame where the door closes. A narrow slot cut into the stop means a kerf-in compression seal, and replacements push straight into the same slot. A flat stop with staple or nail holes means a surface-mounted strip. Taking a short offcut of the old seal to the shop beats measuring.

My new seal made the door hard to close. What now?

Almost certainly oversized for the gap. Fit a thinner profile rather than moving the strike plate. Forcing the latch is what wears the hardware and crushes the seal, and within a year you will have a hard-to-close door that also leaks.

Is foam tape ever the right answer?

For a temporary fix on an interior door or a window, it is fine. On an exterior door in an Ontario winter it compresses permanently, absorbs water and fails within a season. It is a stopgap, not a repair.

Can weatherstripping fix a cold draught at floor level?

No, that is the threshold and the sweep. Many thresholds are adjustable and have simply never been turned up. That costs nothing to try and resolves a surprising number of floor-level draught complaints. If water is also getting in, the sill is involved, and a draught paired with water is worth looking at properly through door repair rather than more product.

How often does weatherstripping need replacing?

By condition rather than by date. Press it: if it springs back, it is working. If it stays compressed, has gone hard, or has cracked at the folds, it has stopped sealing regardless of how it looks. In this climate, checking each autumn is the useful habit.

The Short Version

Measure the gap with a sheet of paper before buying anything. Even gap and a kerf groove means a compression bulb; uneven gap on an older door means metal V-strip; steel door or frame means magnetic is worth considering; sliding doors mean brush. Never layer a new seal over an old one, never size up to be safe, and never try to solve a door that is out of square with a thicker seal.