Short answer

If you can see daylight under or around a closed garage door, or water, dust, leaves or bugs are getting in, a seal is worn, torn or the wrong size. The bottom seal is the one that wears fastest and is usually a straightforward replacement, provided you match it to the retainer on your door. After any bottom seal change, check that the door still closes fully and passes the 2x4 reversal test.

Where the seals are on a garage door

A garage door usually has several separate seals, and each one wears out on its own schedule:

  • Bottom seal. A rubber or vinyl strip along the bottom edge of the door that presses against the floor when the door closes. On many steel doors it slides into an aluminum or vinyl channel called a retainer. On older wood doors it may be nailed or screwed on.
  • Perimeter weatherstripping (stop molding). Strips along both sides and across the top of the door opening, attached to the door frame, with a soft flap that rests against the face of the closed door.
  • Threshold seal. An optional raised strip glued to the garage floor under the door. It gives the bottom seal something to press against and can help with an uneven floor or a slab where water tends to run toward the door.
  • Between-panel seals. Some insulated doors have seals in the joints between sections. These are part of the door's design and are not usually replaced separately.
Where garage door weather seals areOutside view of a closed sectional garage door. Stop molding with a rubber flap runs across the top of the opening (1) and down both sides (2), pressing against the face of the door. The joints between panels (3) close against each other when the door shuts. A rubber bottom seal, often called an astragal, slides into an aluminum retainer along the bottom edge of the door (4). A threshold seal is a raised strip glued to the garage floor under the door (5). The inset shows a cut through the bottom edge: the retainer, the bottom seal and the threshold strip it presses against.123451Stop molding, top2Stop molding, sides3Joints between panels4Bottom seal in its retainer5Threshold seal on the floorCut through the bottomretainerbottom sealthreshold
Seal styles vary by door. Daylight or water at any of these points usually means a seal is worn, torn or out of adjustment.

Signs a seal needs replacing

Stand inside the garage with the door closed and the lights off on a sunny day. Light is the easiest giveaway. Also look for:

  • Daylight along the bottom, especially at the corners or in the middle of the door
  • A bottom seal that is cracked, flattened, brittle or has chunks missing
  • A seal that has pulled partly out of its retainer and hangs in loops
  • Water pooling inside the door after a storm
  • Leaves, dust or insects collecting just inside the door
  • Perimeter strips that are split, stiff or no longer touch the door face

The outside edges of the seals take the full sun, so it is worth a look each spring and again after summer.

Why it is worth doing

Comfort and energy. The US Department of Energy describes caulking and weatherstripping as two simple, effective air-sealing techniques, with weatherstripping used for parts that move, such as doors. The same DOE article notes that gaps between the house and an attached garage can be sealed as part of air sealing, which matters because a leaky garage is hotter in summer and colder in winter.

Water and debris. A worn bottom seal lets rain blow under the door and lets leaves and dust in.

Pests. A gap under the door is an open invitation for insects and small animals looking for shade.

If your garage is attached, the door between the garage and the house matters too. Its weatherstripping and door sweep are separate from the garage door seals and are worth checking at the same time.

Choosing the right bottom seal

Bottom seals are not universal. Family Handyman's overview of garage door bottom seal types describes several common profiles, including:

  • T-style, with T-shaped edges that slide into matching channels in the retainer
  • Bulb-shaped, a closed loop of rubber that flattens against the floor
  • J-style, a flap that bends into a J shape when the door closes
  • U-shaped beaded, a folded strip with beaded edges that fit the retainer channels
  • Self-adhesive or nail-on strips, for doors without a retainer

The key advice from that guide: if your door has a retainer, check the shape of its channels before buying, because rounded and T-style channels are not interchangeable. Measure the width of the door and the size of the largest gap between the door and the floor. A thicker seal can close a bigger gap on an uneven floor, but there are limits, and a badly sloped or cracked slab may need a threshold seal as well.

Easiest route: cut a small piece off the end of the old seal and take it with you, or photograph the end of the retainer, so you can match the profile.

Doing it yourself vs calling a technician

Replacing perimeter weatherstripping on the frame is usually a straightforward job with a saw and nails or screws.

Replacing a bottom seal in a retainer is often manageable too, but it is more awkward than it looks. The door usually has to be partly open to slide the old seal out and the new one in, and the seal can be stiff in cool weather. Keep these points in mind:

  • Unplug the opener or disconnect it so nobody closes the door while you are working under it. If you disconnect it, only pull the release cord with the door closed. See how to open a garage door manually.
  • Do not remove or loosen the bottom brackets at the corners of the door. On most doors the lift cables attach there and they are under high tension.
  • Do not rely on the opener alone to hold a door open while you work under it. Clamp locking pliers on the track just below a roller so the door cannot come down.

Call a local garage door technician if the retainer itself is bent, torn or corroded, the door is wood and the bottom rail is rotting, you are not sure which profile you need, or the bottom corners of the door look damaged.

After replacing the bottom seal: check the door

A new bottom seal can be thicker or softer than the old one, and that changes how the door meets the floor. Chamberlain's travel and force adjustment hub lists problems like a door that comes down, hits the floor and reverses, which can happen when the close limit no longer matches the door. It also says to perform the safety reversal test whenever any adjustment is made.

  1. Run the door down and watch whether it closes fully and stays down, or touches the floor and goes back up.
  2. Run the reversal test: lay a 2x4 flat on the floor in the middle of the doorway and close the door. It must reverse on contact. The federal owner instructions in 16 CFR 1211.16 call for this test monthly and after adjusting the force or travel.
  3. Check the light gap again from inside.

If the door now reverses at the floor, or fails the 2x4 test, the opener's limits need adjusting. That is often simple on newer openers, but if you are unsure, have a technician do it and re-test before you leave the door in use. More on this in opener repair.

What to ask a technician

  • Which seal profile does my door take, and is the retainer in good condition?
  • Is the gap even across the door, or is the floor or door out of level?
  • Would a threshold seal help with water getting in?
  • Will you adjust the opener's close limit if needed and run the 2x4 test?
  • Are the perimeter strips worth replacing at the same time?

If the door has deeper problems, such as damaged bottom panels, see panel replacement. For choosing someone to call, see choosing a technician.

Frequently asked questions

How do I know which garage door bottom seal to buy?

Check the retainer channel shape on the bottom of your door and measure the door width. According to Family Handyman, rounded and T-style channels are not interchangeable. Taking a piece of the old seal with you is the easiest way to match it.

Why does my door reverse after I put on a new bottom seal?

A thicker seal can make the door hit the floor sooner than the opener expects, so it treats the floor as an obstruction. The close limit usually needs adjusting, followed by the 2x4 reversal test. See Chamberlain's adjustment guide.

Can a new seal fix water getting in under the door?

Often, if the old seal is worn. If the floor is uneven or slopes toward the door, a threshold seal glued to the floor may be needed as well. A technician can check whether the gap is even across the door.

Is replacing the weatherstripping worth it in Texas?

It can make the garage more comfortable and keep out dust, water and pests. The Department of Energy calls weatherstripping one of the simplest effective air-sealing steps. For heat, also see garage door insulation and R-value.