A strip of daylight under the door. A puddle after every rain. Leaves and the odd mouse finding their way in. The rubber seal on the bottom of the door wears out long before the door does, and replacing it is a modest job.
In short: If you can see light under a closed door, the bottom seal is worn, the floor is uneven, or both. A new seal fixes most gaps. A sloped or settled floor may also need a floor threshold or a door adjustment. We look at it in person and price it before any work starts.
Wait for a sunny afternoon, close the door, and turn off the garage lights. Walk along the inside of the door and look at the bottom edge. Any light you see is a gap. Then look up each side and across the top. Light there points to the weatherstrip on the frame.
Next, look at the seal itself. Healthy rubber is soft and springs back when you press it. A seal that is stiff, cracked, flat, or chewed at the ends is done. Note where the gap is widest. That tells us a lot.
| Where the gap is | Likely cause | Usual fix |
|---|---|---|
| Even gap the full width | Seal flattened, torn, or shrunk with age | New bottom seal |
| Gap at one end only | Floor slopes, or the door sits out of level | Taller seal, threshold, or door adjustment |
| Gap in the middle | Slab has settled or cracked in the center | Threshold, or a thicker seal to fill the dip |
| Light along the sides or top | Frame weatherstrip is cracked or pulled away | New stop molding weatherstrip |
| Seal hangs out of the channel | Retainer bent or rusted open | New retainer and seal |
Wisconsin winters are rough on rubber. Slush from the car melts in front of the door and freezes the seal to the slab overnight. The next morning, the door lifts and tears the rubber loose from the ice. Do that enough times and the seal comes apart in strips. Road salt dries out the rubber and eats at the metal retainer that holds it. Summer sun on a south-facing door cracks it from the other side.
A frozen seal is also a common reason an opener balks on a cold morning. The door is stuck to the floor, the opener feels the resistance, and it reverses. The steps for breaking it loose without tearing anything are in the frozen-door post.
A gap under the door lets cold air into the garage. In an attached garage, that cold sits against the house wall and the door into the kitchen or mudroom. Water runs in with every storm and pools where you park. Leaves and road grit blow in and pile up in the corners. Mice follow the warm air in the fall.
A seal job is also a good time to look at the bottom section. Rust along the lower edge often hides behind a worn seal. If the steel is gone, the panel replacement page covers the next step.
For more detail on the seal types, see bottom seal replacement in Wisconsin. The frame weatherstrip has its own write-up in weatherstripping replacement.
We replace seals and close gaps for homes in Madison, Fitchburg, Middleton, Sun Prairie, and Verona.
Send us two photos: one of the gap from inside with the lights off, and one of the end of the bottom retainer up close. That is often enough to know which seal to bring. The estimate is free. Seal work fits well into a tune-up visit if one is due.
Look at the metal channel along the bottom edge of the door, called the retainer. Its shape decides the seal. Some take a seal with a round bead on each edge that slides into two slots. Others take a T-shaped edge. An old scrap of the seal, or a close photo of the retainer's end, is usually enough for us to match it.
A floor threshold is a rubber strip glued to the slab under the door. It helps when the floor dips or slopes and a bottom seal alone cannot reach. It also helps keep water from running in. It can get in the way of snow shoveling, so think about where you push the snow.
New rubber is thicker, so the door meets the concrete a bit earlier on its way down. The opener takes that early contact for an obstacle. A small change to the down-limit setting cures it, and we make that change before we leave.
It closes the biggest opening. Mice fit through very small gaps, so cracked weatherstrip along the sides and top of the frame needs attention too.
Early fall suits it. Warm rubber slides into the channel more easily, and a new seal goes into the first freeze at full thickness.
