When water in the ground freezes and thaws, the slab and driveway in front of a garage can move unevenly. That leaves gaps under the door, uneven seal contact and places where meltwater pools and freezes. Look at the threshold each winter, keep water draining away, and call for service if the door binds or the gap keeps changing.
What freeze-thaw does to the ground
The Federal Highway Administration says three things must be present for frost heave: frost-susceptible soil, freezing temperatures in the soil and a source of water. If one is missing, the ground does not heave. It also warns that when conditions are not uniform, differential heaving occurs and causes surface irregularities and cracking.
A driveway apron and a garage slab are pavement sitting on soil, so the same physics applies. One corner can lift while another stays put.
Why the door notices
A garage door seals along a straight line. When the slab or apron moves unevenly, the gap under the door changes from one end to the other. A seal that fit in summer can leave an open corner in February, or it can be crushed on the high side.
FHWA also notes that thawing can weaken the ground, with bearing capacity dropping during mid-winter and spring thaws and recovering over weeks or months. A door that closes cleanly in January may behave differently in March.
Water at the threshold
The ground is only part of it. Garaga warns that water pooling under the door can freeze and make the door stick, which strains the electric opener, and that sand can help for a short time but loses its effect once it is wet. The same page says never to put salt under the door, because it damages the concrete and the rubber seal.
If the door stops partway or will not lift, check the bottom edge for ice before you press the button again. Free it by hand, then run the door once and watch the track. A door that jerks or tilts needs a technician, not a second try.
What to look for each winter
- A gap under the door that is wider at one end than the other
- A seal that is flattened on one side or lifting on the other
- New cracks or a raised edge on the apron just outside the door
- Puddles that sit at the threshold after rain or melting snow
- A door that closes smoothly in the afternoon but sticks in the morning
Take a photo of the gap in the same spot each season. It makes change easy to see and gives a technician something to work from.
Quick answers
Why is there a gap under my garage door in winter?
Freezing and thawing can lift or settle the slab and apron unevenly, so the floor no longer meets the seal along its whole length. A worn seal can cause the same symptom.
Why does my garage door freeze to the ground?
Water that collects under the door freezes and bonds the seal to the slab. Keep the threshold clear and free the door by hand before using the opener.
Is a gap under the door a door problem or a floor problem?
Either. Check whether the gap changes across the width of the door. A gap that is uneven usually points to the floor, and a worn or flattened seal points to the door.
Can freezing damage an opener?
Forcing an opener against a frozen door strains it. Garaga notes that a stuck door can strain the electric opener, so free the door first.
What helps
Keep gutters, downspouts and the driveway slope pointed away from the garage, so water does not feed the ground at the threshold. Clean the bottom seal and treat it with a silicone-based lubricant, as Garaga advises. A seal that bridges small differences, or a threshold seal that sheds water, may be worth asking about when the gap keeps changing.
If the slab itself has moved a lot, that is a paving or foundation question, not a door question. We can tell you whether the door or the floor is at fault. See garage door repair.
Who to call
Emil Garage Doors repairs garage doors, springs, cables and openers and installs new doors in Massachusetts, including Amherst, Chicopee and Pittsfield. Call or send your details with a photo of the gap under the door and we book the soonest visit. See also snow and garage doors.
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