How to install a garage door bottom seal

What you need

• The correct seal, in the right profile and length
• A utility knife
• Dish soap or a bar of soap, plus water
• Pliers
• A second person — not strictly required, genuinely easier
• A wire brush, if the retainer is corroded

If you are not certain what profile you need, identify it before you buy.

Step 1: Open the door to a comfortable height

You want the bottom edge at roughly waist height so you can see into the retainer track from the end. Leave the opener engaged, or if you have released it, make sure the door is held securely — a disengaged door can run down its tracks.

Step 2: Pull the old seal out

Grip one end with pliers and pull it along the track. It usually comes out in one piece. Age, grit and corrosion can make this the hardest part of the job; if it tears, keep working from whichever end still has material to grip. Do not lever against the retainer lips hard enough to bend them, because a bent retainer will not hold the new seal.

Step 3: Clean the track

Years of grit, leaves and dried mud live in there. A wire brush and a rinse are enough. Corrosion inside an aluminum retainer needs the brush, because the new seal has to slide the full width of the door and it will jam on anything raised.

Step 4: The soap trick

This is the whole job, honestly. Mix dish soap with water and coat both the beads on the new seal and the inside of the track generously. A dry seal fights you for the full width of the door. A soaped one slides. It is the difference between fifteen minutes and an hour of swearing.

Step 5: Feed it through

Start both beads into the slots at one end, squaring the seal so it is not twisted. One person feeds and keeps the beads aligned; the other pulls steadily from the far end. Pull straight along the track, not downward — downward pull is what drags a bead out of its slot halfway across.

If it stops, do not force it. Something in the track is catching. Back it off a few inches, find the obstruction, clear it, add more soap.

Step 6: Trim, and check the fit

Leave a half inch or so proud at each end and trim with the utility knife. Then close the door and look along the bottom from inside with the light off. You want even contact across the whole width. A gap in the middle usually means the seal is twisted; gaps at one end mean the floor is not level, and that is the case a floor-mounted threshold exists to solve.

Step 7: Now do the jambs, because you are already out here

This is the step people skip and then wonder why the garage is still cold. Jamb weatherstrip nails or screws to the door frame so that a flexible flap bears against the face of the closed door.

1. Pull off the old strip. It is usually nailed and comes away easily.
2. Close the door. You are fitting the new strip against a closed door, so the flap sits at the right compression.
3. Start at the bottom of one jamb and work up, nailing every 16 inches or so, with the flap just touching the door face.
4. Do the header last, overlapping the tops of both side pieces.

The single most common mistake here is over-compressing the flap. Pressed hard against the door, it drags, wears through in a season and can make the door bind. It should touch, not squash.

Step 8: Check your work in the dark

Close the door, turn the garage light off, and stand inside on a bright day. Any daylight is an unsealed gap, and you now know exactly where it is. On a job done properly there is none.

If there is still a line of daylight along the bottom, measure the gap at both ends and the middle — the measurement guide explains what each pattern means and what to buy next.