Stopping What Comes In Under a Garage Door

Look along the bottom of the closed door from inside. What you see decides which product you need.

An even strip of daylight across the width means the seal on the door has hardened and shrunk. Replace the bottom seal.

Daylight in patches, or water tracking in at one particular spot, means the floor is uneven — and no door-mounted seal will follow a floor that is not flat. That needs a threshold seal bonded to the concrete for the door to close onto.

Getting that diagnosis the wrong way round is why people fit a new bottom seal and still get water.

A note on this guide: this rests on how each seal type works and where garage floors typically fail, not on products tested here. Fitting varies by door type — up-and-over, roller and sectional doors have different bottom rails. See how we test.

The problem, as it appears

A puddle inside the door after heavy rain, leaves banked up against boxes, and eventually droppings in a corner. The door looks shut.

Why the obvious assumption disappoints

The door is not the reference surface — the floor is. Concrete garage floors are rarely level and rarely flat, and many slope very slightly inward from an apron outside. A door can seat correctly along most of its width and still leave a channel a few millimetres deep.

And a new bottom seal cannot bridge a dip. It is attached to the door, so it follows the door. A hollow in the concrete stays a hollow.

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What actually matters

1. A bottom seal, when the seal itself has failed

The rubber hardens, cracks and shrinks with UV and cold. If the gap is even across the width, this is the whole job — and it is a cheap one.

Match the profile to your door's retainer: T-section, bulb and beaded types are not interchangeable, and the retainer on the door tells you which you have.

2. A threshold seal, when the floor is the problem

Bonded to the concrete so the door closes onto it. This is what handles an uneven floor, a slight inward slope, and driving rain that runs along the apron.

Preparation decides whether it lasts. The floor must be swept, degreased and genuinely dry — a threshold seal lifting at one end is nearly always adhesive applied to dust or damp concrete.

3. Not creating a damp problem while solving a water one

A garage with poor ventilation and a newly sealed door traps moisture that previously escaped. For a stored car, standing humidity is worse than a small draught was.

The full measure-first argument is in how damp is your garage — measure first.

4. Finding out whether the door is even the route

Water inside a garage is not always coming under the door. A roof, a wall junction or a blocked outside drain produces the same puddle, and sealing the door achieves nothing.

The diagnosis is in catch a garage leak before it ruins tools and parts.

Where the cheaper option is genuinely enough

Clearing the drainage outside. A blocked gully or a raised apron sends water at the door that would otherwise run away. Free, and it addresses the cause rather than the symptom.

A sandbag or a rolled draught excluder during a storm, if this happens twice a year rather than weekly.

Raising what matters off the floor. Water reaching the concrete is only a problem because of what is standing on it, and the broader argument about protecting a car from the building it sits in is in protecting a car from its own garage.

The mistake to avoid

Buying a bottom seal for an uneven floor. It is the more obvious product and the more common purchase, and on a dipped or sloping floor it changes nothing — the gap it cannot reach is the gap the water uses.

The second mistake is treating a seal as rodent-proofing. It closes the easiest route, which is worth doing, and anything determined will try the frame sides and the corners next.