The short answer
Trace the gap with the door closed, then observe the opening and closing behavior without reaching near moving parts. Side seals can deteriorate, but a persistent gap may reflect jambs, tracks, rollers, door sections, floor slope, or spring balance. A thicker seal can hide the symptom and make the door bind.
Check the boundary
| Area | Observation | What it separates |
|---|---|---|
| Side seal | Compression, cracks, and continuity | Material failure versus alignment. |
| Jamb | Straightness and attachment | Framing movement or damaged trim. |
| Track | Parallel, secure, and clear | Track movement versus seal condition. |
| Door sections | Even contact at multiple heights | Door out of square or damaged hardware. |
| Floor | Slope, gap, and threshold | Building geometry versus door hardware. |
Photograph the gap from a safe position, note whether it appears on one side or both, and record weather or seasonal changes. Do not remove cables, loosen spring hardware, force a stuck door, or disconnect safety features to test the seal.
What a service estimate should separate
Ask whether it includes seal replacement, jamb repair, track alignment, roller or hinge work, door balance, floor or threshold work, and opener safety testing. A weatherstrip estimate should not quietly include high-energy spring work without identifying it.
Related guides
Limits
This is a planning guide, not a garage-door repair procedure. Damaged cables, springs, tracks, or an uncontrolled door need a qualified garage-door professional.