Replace a Garage Door Bottom Seal

Goal

Replace the rubber bottom seal (astragal) on a residential sectional garage door. Compressed, cracked, or rodent-damaged seals let in water, drafts, insects, and rodents - common issues from a 5 - 10 year-old seal. 30-minute repair that fixes a measurable customer pain point (cold garage, mice, leaking on rainy days).

Prerequisites

• New bottom seal matched to the door's track type (P-bulb, T-style, or Cinch-style - three common shapes; bring all three OR confirm at quote)
• Soapy water in a spray bottle (lubricant for sliding new seal in)
• Razor knife OR scissors for trimming
• Tape measure
• 30 - 45 minutes

Steps

1. Identify the seal type. Door track shape determines what seal slides in:

• T-track: T-shaped slots in the bottom rail; T-style seal slides in
• P-track: P-shaped retainer; P-bulb seal slides in
• Cinch / single-channel: one slot; either flat seal or specific brand seal

1. Open the door fully. The bottom rail must be accessible.
2. Remove the old seal. Slide it out one end of the track. May need a flathead screwdriver to start it; once moving, hand-pull works.
3. Clean the track interior with a rag - accumulated dirt prevents the new seal from sliding cleanly.
4. Measure the door width + add 1 - 2". Don't trim until you've test-fit.
5. Spray soapy water into the track as a lubricant.
6. Slide the new seal in from one end. Push steadily; the soap helps. If it binds:

• Check the track for dirt
• Verify you have the right seal profile
• Add more lubricant

1. Center the seal. A small overhang at each end is fine; the seal seats against the track ends.
2. Trim flush with the door edges. Don't trim short - overshooting by 1/4" actually seals better.
3. Close the door. Verify:

• No daylight visible underneath when door is closed
• Seal compresses 1/4" - 1/2" at the floor
• Seal flexes around any floor unevenness

1. Run the door full open + close 3 cycles. Make sure the seal doesn't get pinched at any point in the travel.

Verification

• No daylight at the bottom edge
• Seal compresses appropriately at the floor (not too soft, not too rigid)
• 3 full cycles with no seal binding or pinching
• Customer can feel the difference in draft (open palm test inside the garage on a windy day)

Troubleshooting

• Seal still leaks water in heavy rain: floor isn't level OR door's bottom rail is bent. Inspect with a level. A bent rail = quote a section replacement.
• Seal damages itself within weeks: door is misaligned + comes down off-square. Adjust spring tension + track alignment (separate HowTo).
• Seal won't slide in: wrong profile OR track damaged. Match seal exactly to track profile; a forced-in wrong-profile seal will fail in a year.
• Daylight visible at corners: door panels not aligned. Quote door realignment OR section replacement.

References

• Door manufacturer specifications (each brand has matching seal profiles)
• Manuall internal: Annual Garage Door Service