Weatherstrip
The flexible seal along the bottom, sides and top of a garage door that closes the gap between door and opening.
- Outer steel skin, facing the street
- Insulating foam core — this is what R-value measures
- Inner steel skin, facing the garage
- Aluminium retainer holding the seal
- Bottom seal, compressed against the floor
The bottom seal — sometimes called an astragal — is a rubber or vinyl strip in a retainer along the base of the door. It compresses against the floor to keep out water, draughts, leaves and rodents, and it is the part that perishes first because it takes the most abuse.
Replacing a bottom seal is inexpensive and is genuine homeowner work on most doors: the old strip slides out of the retainer and the new one slides in. Side and top seals are nailed or screwed to the frame.
A door that leaves a visible gap at one end when closed is more often a levelling or limit problem than a seal problem, so check the floor is level before buying a thicker seal.
Replacing a bottom seal is one of the few garage door jobs that is genuinely straightforward. With the door closed, the old strip slides out of the aluminium retainer at the base and a new one slides in, often helped by a little soapy water. Buy by the retainer profile rather than by eye, since the T-shaped and bead-shaped types are not interchangeable. Before buying a thicker seal to close a stubborn gap, check whether the floor is level and whether the door is sitting square, because a gap at one end only is usually a levelling or limit problem wearing a seal-shaped disguise.
Bottom seals come in a few incompatible profiles — T-ends, bead-ends and U-shapes — and the retainer on your door accepts only one, so take a short offcut with you or photograph the end profile before buying. Cold matters too: vinyl stiffens and cracks in freezing weather, so a seal that has survived several winters is often perished rather than merely dirty. Where the garage floor slopes or has settled, a threshold seal bonded to the floor is the better answer than a thicker bottom seal; it rises to meet the door instead of asking the door to close onto an oversized strip.