Water Leaking Under the Garage Door
Water seeping under your garage door is almost always one of two things: a worn-out bottom seal that no longer presses tight against the floor, or grading and drainage outside that's funneling water straight at the door. Start by checking the rubber bottom seal and the threshold for gaps, then look at where the water is actually coming from outside. A fresh seal or a threshold strip fixes the majority of cases for under $40, but if water is pooling because of how the driveway or yard slopes, you'll need to redirect it.
Step by step
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1
Find out where the water is actually getting in
Before you buy anything, watch what happens during the next rain (or hose down the apron with a garden hose). Is water coming straight under the middle of the door, creeping in at the corners, or running down the driveway and pooling against the threshold? Water at the corners usually means worn weatherstripping on the sides; water under the center points to a bad bottom seal or a low spot in the slab; a sheet of water flowing toward the door is a drainage problem outside, not a door problem. Knowing which one you have saves you from fixing the wrong thing.
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2
Inspect the bottom rubber seal (the astragal)
Close the door and look at the flexible rubber strip along the very bottom from the inside. It should mash flat against the floor and seal the whole width. Run your hand along it, hold a flashlight on the far side at night, or look for daylight. If it's cracked, brittle, torn, or has flattened out and stopped springing back, it's done. Bottom seals are cheap (roughly $15-$30 for a universal kit) and slide into the retainer track on the bottom of most metal and many wood doors. Match the T-style or bead-style end to your existing retainer so the new one slides in.
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3
Check whether the floor itself is the problem
Lay a level across the garage floor right at the door. A lot of older slabs settle and develop a low spot or dip right at the opening, so even a brand-new seal can't make full contact. If you find a dip, a rubber or aluminum threshold seal glued to the floor is the fix. It builds up a small dam (about a half inch) that the door closes against and that blocks water from rolling in. Threshold kits run about $25-$50 and install with adhesive on a clean, dry floor — just know they also create a small lip you'll roll over with a car.
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4
Replace or upgrade the weatherstripping that's failed
For a worn bottom seal, pull the old rubber out of the retainer (spray a little soapy water in the track and it slides), then feed the new seal through. For side and top gaps, replace the vinyl weatherstrip nailed to the doorstop molding. If you've confirmed it's a slab/threshold issue, install the threshold strip from the previous step instead — or use both a new bottom seal AND a threshold for a stubborn leak. Many homeowners get the best results combining a fresh astragal with a threshold.
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5
Redirect the water coming from outside
If water is flowing toward the door across the driveway or apron, no seal will hold it back forever — you have to give the water somewhere else to go. Options, cheapest first: re-grade the soil along the sides so it slopes away from the door, clean out or extend gutter downspouts that dump near the driveway, install a trench drain (channel drain) across the apron in front of the door, or add a small concrete or rubber speed-bump-style berm to deflect runoff. A trench drain is the gold-standard fix for a driveway that pitches toward the garage, but it's a bigger job that usually means cutting concrete.
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6
Seal up the small stuff and test
Caulk any cracks in the concrete apron and along the bottom of the door frame where water can wick through. Make sure the door is closing fully and squarely — a door that's out of level on one side leaves a wedge-shaped gap that lets water in at one corner. Then test with a hose before the next storm so you know the fix actually worked rather than waiting on the weather.
When to call a pro
Call a pro if water keeps coming in after you've replaced the seal and threshold, if your garage floor has a significant dip or the slab is cracked and heaving, if you need a trench drain or concrete cut to fix driveway drainage, or if the door is visibly out of alignment and won't close level — those last two are jobs where a botched DIY costs more than the repair.
Call (888) 290-7421Frequently asked
Why is water coming under my garage door when it didn't used to?
Almost always because the rubber bottom seal has aged out — it gets brittle and flattens over a few years, so it stops pressing tight against the floor. Settling of the concrete slab (creating a low spot at the opening) and changes in your yard's drainage, like a downspout that got redirected or landscaping that changed the grade, are the other common culprits. The leak appearing 'suddenly' usually just means the seal finally crossed the threshold from worn to failed.
How much does it cost to stop water from leaking under a garage door?
The DIY fixes are cheap: a universal bottom seal kit runs about $15-$30, and a threshold seal kit is roughly $25-$50, both installable in an afternoon. If the real problem is drainage, costs climb — a professionally installed trench drain across the apron typically runs several hundred to over a thousand dollars depending on length and whether concrete has to be cut. Start with the seal and threshold; most people never need the bigger job.
Should I use a bottom seal or a threshold seal?
A bottom seal attaches to the door itself and is the right first move when the seal is simply worn out. A threshold seal glues to the floor and is the better choice when your slab has a low spot or dip that a door-mounted seal can't bridge. For a tough leak, using both together gives you two lines of defense. The one tradeoff with a threshold is the small raised lip you'll drive over.
Can water under the garage door cause real damage?
Yes, over time. Standing water rusts the bottom of a steel door and corrodes the rollers and hardware, it can ruin anything stored on the floor, and in a garage with drywall or wood framing it invites mold and rot. In cold climates, water that freezes at the threshold can seal the door to the floor and strain the opener. It's worth fixing promptly rather than mopping after every storm.
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