The short answer
Water under a garage door is a water-path problem, not automatically a gasket problem. Look at the door’s bottom seal, side seals, threshold contact, slab slope, driveway, gutters, and nearby downspouts together. A new rubber seal cannot stop water that flows around the jamb or ponds against an uneven floor.
Check each boundary
| Boundary | Observation | What it separates |
|---|---|---|
| Bottom seal | Cracks, flattening, gaps, or light under the door | Door-to-floor contact. |
| Threshold | Continuous contact and secure edges | Water that runs toward the door. |
| Side seals | Compression and gaps at both jambs | Wind-driven rain and splash. |
| Slab | Low corner, crack, or standing water | Building drainage versus door hardware. |
| Exterior runoff | Downspout, driveway, and roof water | The source may be outside the door. |
Clean the contact area and photograph it closed. Do not place fingers near hinges, rollers, cables, or a moving door. If the door is difficult to balance, reverses unexpectedly, or has damaged cables, stop the weather-seal project and call a garage-door professional.
Compare replacement materials
Measure the existing retainer, seal profile, door width, and threshold height before ordering. Bottom seals either fasten directly to the door or slide into a retainer. M-D’s 03749 , for example, is a 16-foot by 2-inch by 1-inch black rubber strip that fastens with nails or screws, so it doesn’t replace an insert on a door built with a slide-in retainer track; that door needs the matching insert profile. A thicker seal may reduce clearance or change the door’s closing force. The estimate should separate seal, retainer, threshold, slab or drainage work, and any opener or alignment service.
Related guides
Limits
This guide does not authorize spring, cable, track, or opener adjustment. Those components can cause serious injury when handled incorrectly.