Garage Door Perimeter Weatherstrip: step by step

When the work is finished you have a door that closes against a soft, continuous line of contact on both sides and across the top. From inside with the lights off there is no daylight at the edges; from outside, the new stop matches the trim colour. The door moves through its full travel without the fin catching or squealing. You are told what profile, colour and lengths were fitted, so a match is simple later, and shown the few habits that keep the seal supple: no paint on the fin, a silicone wipe before freezing rain, and slush kept off the bottom of the jambs.

A daylight test from inside

The first check needs no tools. The door is closed, the garage lights go off, and the technician stands inside looking along each side and across the header for lines of daylight. A bright, even line means the fin has shrunk back or hardened; a wedge that widens toward the top or bottom points to the door sitting out of square; a gap only at a corner means the pieces were never overlapped. On a windy day a hand or a smoke pencil along the edge finds drafts that daylight misses. The pattern of the gaps is what tells the technician whether the seal alone is the answer or whether the door needs a small adjustment first.

The header piece goes on first

With the door closed, the header length is cut to the full width of the opening and lifted into place, a two-person job on a double door. It is positioned so its fin lies against the top section with a slight, even deflection along the whole width, then fastened from the centre outward with galvanized or stainless nails or exterior screws at regular spacing, which keeps the length straight rather than letting it wander. The ends are left to receive the side pieces beneath them. Fitting the header first means both sides are cut to meet it exactly, and the corners close properly.

If the door changes, the seal is re-checked

The seal was set against the door as it sits today. If the door is later adjusted, has its springs or rollers replaced, or is swapped for a new one, the contact can change: a door that now sits a few millimetres further out presses the fin harder, and one that sits further in leaves a gap. After any such work, do the daylight test again and ask the technician doing that job to check the perimeter seal while they are there. Re-setting a length is a small task and keeps the two parts of the system working together.