How do I stop draughts, water and leaves coming under a garage door?

Up-and-over doors need a running clearance at the bottom and the floor is rarely flat, so there is almost always a gap. That gap lets in wind, leaves, rain, and in some garages a steady stream of water off the drive. Sealing the door helps with three of those four. The fourth is a drainage problem in disguise and no seal will fix it.

Safety

What you'll need

• Bottom seal section suited to the door type
• Threshold seal, if the floor is very uneven (optional)
• Fixings or adhesive as specified for the seal
• Brush strip for the sides, if needed
• Tape measure, knife and a straightedge
• Channel drain, if water is running in (optional)

Step by step

1. Work out whether it is wind or water.Draughts and leaves are a sealing problem. A pool that appears inside after rain is a drainage problem: water is running down the drive to the door and there is nothing to stop it. Watch it in rain before buying anything, because the two have completely different fixes.
2. Measure the gap along the whole width.Close the door and check the gap at both ends and in the middle. Concrete garage floors slope and settle, and a 5mm gap at one end and 25mm at the other is common. The largest gap decides the seal you need.
3. Choose a seal that deforms.A rigid strip will only ever touch the floor where the gap is smallest. A flexible bulb or blade seal, or a brush strip, compresses to the floor across its whole width and copes with an uneven surface. That flexibility is the whole point.
4. Fit the bottom seal to the door.Most fit to the bottom edge or the inside face of the bottom rail, screwed or in a retaining channel. Fit it with the door closed so you can set it against the actual floor, and check the door still operates through its full travel without the seal fouling.
5. Add a threshold seal for a large or very uneven gap.A moulded rubber threshold bonded to the floor, which the door closes against. It handles gaps a door seal cannot and it also stops water running in under moderate conditions. It has to be positioned exactly, so mark the door's closed position first.
6. Seal the sides and the head if they leak too.Brush or blade seals down the frame's sides and along the head deal with the draughts a bottom seal cannot. On many doors these are available as a kit for the specific model.
7. Fix the water outside, if that is what is happening.A fall away from the door across the apron outside, and a channel drain across the opening connected to a lawful outfall. This is the answer for a garage that floods, and it is the only answer — no seal holds back running water.
8. Keep the ventilation.Garages need air movement, particularly if there is a car, fuel, a freezer or any combustion appliance in them, and they condense badly when sealed tight. Seal the bottom gap and keep or add high and low vents that are not in the door's path.
9. Check it through a full cycle.Open and close the door several times. The seal should touch without dragging, the door should not need extra force, and nothing should be catching in the tracks.

Tips

• Fit the seal in mild weather. Rubber sections are stiff in the cold and much harder to work with and position accurately.
• A brush strip is more tolerant of a rough floor than a rubber blade and lets a little air through, which is often the right compromise in an unheated garage.
• If the garage has a freezer or a fridge in it, ventilation matters more than sealing. They need air and the garage needs to not condense.
• Check the seal every autumn. Rubber perishes, brush strips wear flat, and both are cheap to replace.
• A garage floor that dishes badly can be levelled with a floor levelling compound, but check the door clearance before adding any thickness at the door line.

Common mistakes

• Building a step or a kerb across the opening — It catches the door on its travel, it is a trip hazard, and it holds water on the outside of it. A channel drain does the job without any of those problems.
• Fitting a rigid seal to an uneven floor — It contacts at one point and gaps everywhere else, and it can bind the door where it does touch.
• Sealing the garage completely — An unventilated garage condenses. Cars, bikes and tools rust, and anything stored in it gets damp. Seal the draughts at the bottom and keep the deliberate ventilation.
• Expecting a seal to solve a flooding problem — Running water finds every gap and pushes seals aside. If water arrives at the door, the fix is drainage outside it.

If it doesn't work

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