Water Coming Under the Garage Door? Find the Cause Before You Buy a Seal

Question 01

Why is water coming in under my garage door?

Most leaks under a garage door come from one of five things: a bottom seal that has cracked or flattened, a door that stops a little above the floor, a door that sits crooked, gaps at the sides, or water running down the driveway toward the door. The pattern of the water on the floor tells you which.

Question 02

How do I find where the water is getting in?

Look on a dry day, then again while it rains. With the door shut and the garage lights off, daylight shows every gap along the bottom and sides. Next rain, watch where the water first appears. A wet line along the whole door points to the seal, and a wet corner points to a gap there.

1. 01Close the door fully and stand inside with the lights off. Note where light shows along the bottom and up each side.
2. 02Look along the bottom of the door from one end to the other. An even gap means the door stops short. A gap that tapers means the door or the floor isn't level.
3. 03Check the seals by eye. B&D says to pay attention to the bottom seal, the side seals and the top strip.
4. 04In the next heavy rain, look at where the water first comes in, and whether it's coming under the seal or running down the driveway.
5. 05Clear any leaves, sand or grit from under the bottom seal. Debris stops the seal sitting flat on the floor.
6. 06Watch the door close once on the opener. If it stops early, bounces back up or sits crooked, the seal isn't the first thing to fix.

Question 03

How do I know if the bottom seal is worn out?

A worn bottom seal is cracked, brittle, flattened or pulling away from the door. B&D says rubber flattens after years of use and leaves small channels for water to seep in. Water pooling inside the door after a downpour, more draughts and a door that rattles as it closes are the other signs.

B&D describes the bottom seal as a barrier between the door and the floor that keeps out rain, dust, pests and draughts. It needs to stay flexible to seal along the full width of the door. According to B&D, the signs it has aged out are:

• Cracks, brittleness or flat spots, or sections pulling away from the door.
• Water pooling along the edges just inside the door after heavy rain.
• Draughts or a hotter garage in summer. B&D says even a few millimetres of gap lets air in.
• Pests getting in, with chew marks or fraying along the bottom edge.
• Rattling or vibration as the door closes, because a hardened or warped seal no longer cushions the door.

Salt and sand wear seals faster near the beach. Rinsing the grit out of the seal line is part of the routine in the salt air and rust guide.

Question 04

Which garage door seals keep rain out?

Four kinds work together: the bottom seal on the door, a threshold seal fixed to the floor, brush or bristle seals along the top and sides, and sealant around the frame. A threshold helps where water runs in, though B&D says some can still get past in heavy rain.

Steel-Line says its nylon brush seal is rated UL94-V2 and suits ember protection under AS3959, the bushfire building standard. That matters more on bush blocks than on the coastal strip.

No seal fixes a door that doesn't reach the floor, or one that sits crooked. Sort that first, or a new seal just wears unevenly.

Question 05

Why does my garage door stop short and leave a gap at the floor?

A door that stops a little above the floor often has an opener problem or a door problem, not a seal problem. Merlin's manual says that when the door stops and the light flashes, the door was obstructed and couldn't reach its normal stopping position, or it has become very heavy to operate. A door that binds in its tracks or has lost its balance can make the opener stop early.

Merlin's troubleshooting guide says a door that can't reach its normal stopping position has been obstructed or has become very heavy, and it lists changed force or travel limit settings among the reasons a door stops part way. Its advice is to pull the manual release and check the door moves easily by hand through its full range, and to have the door repaired or serviced if it's heavy to move by hand. A door that's stiff or heavy by hand needs repairing before anything is changed on the opener.

Merlin also says force sensitivity should only be adjusted by a professional installer able to test the force at the bottom edge of the door. Turning the force up to push the door down further takes away the protection that stops it on a person, a pet or a car.

If the door reverses as soon as it touches the floor, read how the safety sensors and auto-reverse work. Every Deadlock garage door service tests the opener's limits, force and safety reverse.

Question 06

How do I fix the gap at the bottom of my garage door?

Go by the shape of the gap. An even gap along the whole door can mean the opener's close limit has shifted or the door is binding, so check it moves freely by hand first, and test the safety reverse after any change. A worn seal means a new seal that fits your door. A gap wider at one end means a crooked door or an uneven slab, so leave it and call.

• Even gap, door runs freely by hand: your opener's manual explains how its travel limits are set. After any change, test the safety reverse with a roll of paper towel laid flat under the door. Merlin asks owners to check monthly that the door reverses on a 50mm object on the floor.
• Even gap, door stiff or heavy by hand: don't touch the opener settings. The door needs a repair first.
• Seal flattened or cracked: the seal needs replacing with one matched to your door. Clear grit from the channel and the floor first.
• Gap wider at one end: the slab may not be level, or a cable may have stretched on one side. Don't loosen or adjust anything at the bottom corners.

B&D says a technician checks the door's alignment, spring tension and sealing performance. Repairs and servicing are booked as a callout valued between $200 and $300, depending on the door size and the labour involved. Call 0402 882 653 or book a callout.

Question 07

Can a garage door keep out floodwater?

No. B&D says even with a threshold seal some water may still get in during heavy rain, so a door seal won't hold back running floodwater. Sunshine Coast Council says sandbags won't stop flooding entirely either, but placed well they cut the water coming in. For a flood-prone garage, build a low sandbag wall across the roller door to at least the expected flood height.

Sunshine Coast Council's sandbag advice, in short:

• Don't wait for a flood warning to get sandbags. Sort them before storm and cyclone season if your property has flooded before.
• Most homes on a concrete slab can be protected with fewer than 25 sandbags.
• A filled sandbag weighs 15 to 20 kilograms, so take care lifting them, especially on your own.
• Build a small wall across doorways and roller doors to at least the expected flood level, and keep at least one door you can still open.
• Putting sandbags in plastic bags gives them more water resistance.