How to replace a garage door bottom seal

On most steel garage doors the bottom seal is a rubber or vinyl strip that slides into a metal channel on the bottom edge of the door, so replacing it means sliding the old strip out of that channel and feeding a new one of the same shape back in. With the opener unplugged, the door held partway open, some soapy water and a helper, it is usually an afternoon job. The two things that catch people out are buying the wrong profile for the channel, and a door that will not close properly afterward because the new seal is thicker than the old one.

October is when this question comes up here. The first seasonal freeze in the Pikes Peak region usually arrives in the first week of the month, and that is when a cracked or flattened seal starts letting in cold air, blowing leaves, snowmelt and the occasional mouse. Below is how to tell whether the seal is really the problem, how to replace it safely, and the Colorado Springs details that wear seals out faster than in most places.

First: is it the seal, or is the door not sitting level?

Close the door, turn off the garage light in daytime and look at the bottom edge from inside. Where the light shows tells you what you are dealing with.

• Light along the whole width, and the rubber is cracked, flat or torn. That is a worn seal. Replacing it is the fix.
• Light only in the middle, or only in one low spot. The slab has a dip, which is common where concrete has settled. A taller bulb-style seal, or a threshold seal on the floor, closes that gap better than a straight swap.
• A gap that tapers from nothing on one side to wide on the other. The door itself is not level. That usually means the lifting cables are wound unevenly or a spring is out of balance, and a new seal will not hide it for long. Do not try to adjust the cables or the bottom brackets yourself; they hold the spring's tension.
• The metal channel is bent, rusted through or pulling away from the door. The retainer itself needs replacing. On most doors it sits right next to the bottom brackets where the cables attach, so this part is a service call rather than a weekend job.

Which bottom seal fits your door

Bottom seals are not universal. The rubber has to match the shape of the channel it slides into.

• Look at the end of the door. With the door partly open, look at the end of the bottom edge. You will see either an aluminum channel with two slots (most common on steel doors), a single slot, or no channel at all with the seal nailed or screwed to a wood door.
• Match the edge shape. The strip's edges are made to fit the slots: T-shaped, bead-shaped or flat. Cut a short piece off the old seal and take it to the store, or send a clear photo of the end.
• Match the width and size. Measure the channel width and the door width. Buy a strip a little longer than the door.
• Pick the profile for the gap. A standard flat or J-style seal is fine on a level slab. A bulb or taller profile handles an uneven slab better.

How to replace a garage door bottom seal, step by step

1. Unplug the opener. Nobody should be able to press a button while you are working under the door.
2. Raise the door to about chest height and lock it there. Clamp a pair of locking pliers on the track just under a roller on each side so the door cannot drift down. If the door will not stay put on its own or feels heavy, stop: that is a spring problem, and you should not be working under it.
3. Slide the old seal out. Pull it out from one end of the channel. If the ends of the channel are crimped, open them gently with pliers. Old rubber that has fused to the channel may need cutting out in pieces.
4. Clean the channel. Wipe out the dirt, grit and old rubber so the new seal slides freely. Check that the slots are not pinched closed anywhere along the width.
5. Warm and lubricate the new seal. Cold rubber is stiff and fights you. Let it sit indoors first, then wipe the edges with soapy water.
6. Feed it in with a helper. One person lines up both edges in the slots at one end and feeds; the other pulls from the far end. Keep it straight so it does not twist inside the channel.
7. Trim and secure the ends. Cut the strip so it covers the full width of the door, then lightly crimp the ends of the channel so the seal cannot walk out over time.
8. Close the door by hand first. Remove the pliers, lower the door slowly and look at the seal. It should compress a little along the whole width, not be crushed flat.

The step people skip: the opener and the safety reverse

A new seal is often thicker than the flattened one it replaces. The opener can read the extra thickness as an obstruction and send the door back up just before it closes. That is why "garage door won't close after replacing seal" is such a common search.

• Adjust the close limit, not the force. Follow the opener's manual to set where the door stops on the way down. Turning up the force to push past the seal makes the safety reverse less sensitive.
• Run the reversal test afterward. Lay a flat 2x4 on the floor under the middle of the door and close it. The door should touch the board and reverse. If it crushes the board and stays down, do not use the opener until it is adjusted.
• Check the photo eyes. Make sure nothing you moved or knocked while working is blocking or misaligning the sensors near the floor.

If the opener still will not close the door properly after the limits are set, our garage door opener repair page covers the usual causes.

Threshold seals: when a bottom seal is not enough

A threshold seal is a raised rubber strip glued to the floor where the door lands. It works with the bottom seal, not instead of it, and it helps most on a slab with a dip, or where melting snow runs back toward the garage. Two cautions here: it needs a clean, dry slab and a mild day for the adhesive to cure, so it is a fall job rather than a January one, and a snow shovel catching the edge can tear it loose.

The Colorado Springs part

• Sun at altitude. At around 6,000 feet, UV dries out rubber faster. South- and west-facing doors usually need a new seal sooner.
• Freeze, thaw, freeze. A fall day can start below freezing and end mild. Snowmelt that runs under the door in the afternoon can freeze the seal to the slab overnight. Each time the door tears it free, the seal loses a little more.
• Wind and dust. Wind pushes dust, leaves and snow through a small gap, which is also how mice get into garages in the fall.
• Higher up, colder sooner. Homes in Monument, Woodland Park, Black Forest and Palmer Lake usually get hard freezes earlier and longer than central Colorado Springs, so a worn seal shows up there first.

If the seal is frozen to the floor

Do not let the opener rip it free; that tears the seal and strains the opener. Loosen it with gentle warmth, such as a hair dryer, or a plastic scraper along the edge, then open the door. Clear slush from the line where the door lands before a cold night. A light coat of silicone spray on the rubber makes it less likely to stick. If you hear crackling or popping as the door lifts on cold mornings, our guide to why a garage door is loud in cold weather explains which noises are harmless.

When it is worth a visit instead

• The gap is wider on one side than the other, or the door hangs crooked.
• The bottom channel is bent, rusted through or loose, or a cable at the bottom corner looks frayed.
• The door will not stay put when held partway open, or it feels heavy to lift by hand.
• The door will not close properly even after the opener limits are set.

We check and replace bottom seals during a visit for garage door maintenance in Colorado Springs. That visit also covers the balance test, rollers, hinges, tracks and the opener safety check. Uneven doors, damaged retainers and cable problems are part of garage door repair.

The short version

To replace a garage door bottom seal, unplug the opener and lock the door partway open. Slide the old strip out of the bottom channel and clean the channel. Then feed in a new seal of the same profile, using soapy water and a helper, and crimp the channel ends. Before you use the opener again, set its close limit and run the 2x4 reversal test. If the gap is uneven from side to side, or the channel or cables are damaged, the seal is not the real problem.

Frequently asked questions

Can I replace a garage door bottom seal myself?

On most steel doors, yes, as long as the door is locked in place, the opener is unplugged, and you leave the bottom brackets and cables alone. Replacing the metal retainer channel is a different job, because it sits next to parts under spring tension.

Why won't my garage door close after replacing the seal?

The new seal is usually thicker, so the opener reads it as an obstruction and reverses. Reset the close limit using the opener's manual, then run the reversal test with a flat 2x4. Do not fix it by turning up the force.

How do I know which bottom seal to buy?

Match the shape of the edges to the slots in the channel, and match the channel width. Taking a short piece of the old seal to the store is the easiest way to get it right.

How often should a garage door bottom seal be replaced?

There is no fixed schedule. Check it every fall before the first freeze, and replace it when it is cracked, flattened, torn, or letting in daylight. In this climate, doors facing strong afternoon sun usually need it first.

Should I add a threshold seal too?

Only if the slab has a dip or water runs in under the door. On a level slab with a good bottom seal it adds little. Install it on a mild, dry day so the adhesive cures.