Water shows up across most of the opening
A damp strip or shallow puddle runs along the inside edge of the closed garage door after rain.
Start here: Start with the garage door bottom seal and the floor slope just outside the opening.
Garage Door Leak
Garage Door Water Coming Under Door
Direct answer: Water coming under a garage door is usually caused by runoff hitting the door, a flattened or torn garage door bottom seal, or a slab that slopes back toward the garage instead of away from it.
Most likely: Most of the time, the first thing to check is the garage door bottom seal and whether the wet line runs evenly across the opening or only at one corner.
Start outside and trace where the water is actually traveling. A garage door can look like the leak source when the real issue is driveway runoff, a low spot at one corner, or a door that is not sitting flat on the slab. Reality check: even a good seal will not hold back standing water for long. Common wrong move: adding more sealant before checking whether the slab is pitching water straight at the opening.
Don’t start with: Do not start by smearing caulk across the threshold or replacing random door parts. If the water path is wrong, caulk just hides the real problem for one storm or two.
Wet across the full width?Check the garage door bottom seal first, then look for a slab low spot or back-pitch toward the door.
Wet at one corner only?Look for a twisted bottom section, side gap, or runoff concentrating at that corner before replacing anything.
Last reviewed: 2026-04-05
What the leak pattern is telling you
Water comes in at one bottom corner
One corner gets wet first, while the rest of the opening stays mostly dry.
Start here: Check for concentrated runoff, a side gap, or a bottom section that is not touching evenly.
Water appears even when rain is light
A small amount of rain still leaves a wet line inside the garage.
Start here: Look for a hardened or flattened garage door bottom seal that no longer conforms to the slab.
Water only comes in during heavy storms or wind-driven rain
The garage stays dry in normal rain but leaks when water is blowing sideways or pooling outside.
Start here: Check for standing water at the driveway edge, side weather seal gaps, and whether the door opening is taking direct runoff.
Most likely causes
1. Worn or flattened garage door bottom seal
This is the most common cause when water tracks under the full width or when the seal looks hard, cracked, or compressed flat.
Quick check: With the door closed, look from inside for daylight under the bottom edge and feel for spots where the rubber is stiff or torn.
2. Driveway or slab slopes water toward the garage
If water pools outside the door or rushes toward the opening during rain, even a decent seal can be overwhelmed.
Quick check: During or right after rain, look for a wet path flowing toward the door instead of away from it.
3. Gap at one side from uneven door contact or damaged side weather seal
Corner leaks usually point to a localized gap, not a full-width seal failure.
Quick check: Close the door and inspect both bottom corners and side edges for visible light, uneven contact, or missing side seal.
4. Door bottom section is out of line or the opening is not sealing evenly
If the bottom edge touches in the middle but not at one end, water will find that low corner every time.
Quick check: Stand outside with the door closed and compare how the bottom edge meets the slab from left to right.
Step-by-step fix
Step 1: Watch where the water is coming from before touching the door
You want the source path, not just the wet spot inside. Most wasted fixes happen when people seal the opening without checking whether runoff is being driven straight at it.
- Look outside during rain if you can do it safely, or hose the driveway lightly and watch where the water travels.
- Check whether water is pooling against the garage door, running down the driveway toward it, or only collecting at one corner.
- Mark the first wet area inside with painter's tape or a pencil so you can match it to the outside path.
- If the water is clearly coming from one corner, focus the rest of your checks there first.
Next move: If you can clearly trace the water path, you will know whether to focus on the seal, a side gap, or outside drainage. If you cannot tell where the water starts, move to the closed-door gap check and inspect the seal itself.
What to conclude: A full-width wet line usually points to bottom seal contact. A single-corner leak usually points to runoff concentration, side gap, or uneven door contact.
Stop if:
- Water is entering fast enough to threaten stored items, drywall, or outlets near the floor.
- You find water coming from the wall, jamb, or ceiling instead of under the door.
Step 2: Check the garage door bottom seal with the door fully closed
A bottom seal that is torn, hardened, or flattened is the most common direct failure on this symptom.
- Close the garage door fully and disconnect the opener only if you need to move the door by hand for a closer look.
- Inspect the garage door bottom seal from end to end for splits, missing sections, brittle rubber, or a shape that has gone flat.
- Look from inside for daylight under the bottom edge, especially at the corners.
- Run your hand along the inside bottom edge and note any spots where the seal is not touching the slab at all.
Next move: If the seal is visibly damaged or there is a clear gap under the door, replacing the garage door bottom seal is the right next move. If the seal looks good and contact is even, the leak is more likely being driven by slope, pooling, or a side gap.
What to conclude: A bad seal is a real repair path. A good-looking seal with heavy pooling outside usually means the water load is the bigger problem.
Step 3: Separate a side-gap leak from a bottom-seal leak
Corner leaks get misread all the time. If water is sneaking around the edge instead of under the middle, the fix changes.
- With the door closed, inspect both side edges from inside and outside for missing, curled, or crushed garage door side weather seal.
- Check whether one bottom corner sits higher than the other or whether the bottom section looks slightly twisted.
- Look for rub marks, dirt trails, or a clean water track at one jamb where water has been slipping past repeatedly.
- If one corner leaks, compare that corner's seal contact to the dry side.
Next move: If you find a clear side gap or damaged side seal at the leaking corner, that is the repair to make first. If the sides look tight and the corner still leaks, the slab may dip there or runoff may be concentrating at that corner.
Step 4: Check the slab and driveway for back-pitch or a low spot
A garage door seal is meant to shed normal runoff, not hold back a small pond. If the concrete pitches the wrong way, the leak will keep coming back.
- Lay a straight board or level across the threshold area and check whether the surface outside falls away from the garage or back toward it.
- Look for a birdbath low spot where water stands after rain, especially near the leaking corner.
- Check whether downspout discharge, landscaping, or a driveway rut is sending water directly at the opening.
- If the door seal is decent but water pools against it, correct the drainage path before expecting the door to stay dry.
Next move: If you find standing water or back-pitch, address the drainage issue first and treat the door seal as secondary unless it is also damaged. If the slab drains away properly and there is no pooling, go back to door fit and weather seal contact.
Step 5: Make the repair that matches what you found, then test it with controlled water
Once you know whether the problem is seal failure, side leakage, or drainage, you can fix the right thing and verify it before the next storm.
- Replace the garage door bottom seal if it is torn, hardened, or not contacting the slab evenly.
- Replace the garage door side weather seal if one side is visibly damaged or leaving a corner gap.
- If runoff is the main issue, redirect water away from the opening and clear any simple obstructions that are concentrating flow near the door.
- After the repair, close the door and run a gentle hose test starting low and slow outside the opening. Do not blast water directly upward into the seal.
- If the door still leaks at one corner after seal replacement, the door may need adjustment by a garage door pro rather than more parts.
A good result: If the inside stays dry during a controlled test and the next rain, you fixed the actual entry path.
If not: If water still comes in with good seals and no pooling, the door is likely not sitting square on the slab and needs professional adjustment.
What to conclude: A successful hose test confirms the repair. A repeat leak after good seal replacement usually points to door alignment or slab shape, not another random part.
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FAQ
Why is water coming under my garage door even with a new seal?
A new garage door bottom seal will not solve pooling water or a slab that pitches back toward the opening. If the seal is new and the leak remains, check for standing water, a low corner, or a side gap before replacing anything else.
Can I just caulk the bottom of the garage door shut?
No. The door needs to move, and blind caulking usually traps dirt, wears off quickly, and hides the real source. Fix the water path or replace the correct weather seal instead.
Why does my garage door only leak at one corner?
That usually means the problem is localized. The common causes are runoff concentrating at that corner, a damaged garage door side weather seal, a low spot in the slab, or a door bottom edge that is not sitting flat there.
Is a garage door threshold seal the first thing to try?
Not usually. A threshold can help in some situations, but it should not be your first move if the bottom seal is damaged or the driveway is sending water straight at the opening. Diagnose the water path first.
How do I know if the slab slope is the real problem?
If water visibly runs toward the garage, stands against the closed door, or keeps leaking past a decent seal, the outside slope is likely the main issue. A level or straight board across the threshold area will usually make that clear.
Should I adjust the garage door to press harder on the floor?
Only with caution. Too much downward force can create other problems and still will not fix standing water. If the door is obviously out of square or not sitting evenly, a garage door pro is the safer call.