Stop Water Entering Your Garage After a Hot Summer

A wet garage floor is frustrating enough the first time. When it happens every time there’s heavy rain, you want to know what will actually stop it, rather than spend another afternoon moving boxes and sweeping water back outside.

 

 

The gap under the garage door is a good place to start, but it isn’t always the whole problem. Water can get around the sides, collect in a dip in the floor or run down a driveway that slopes towards the garage. Each needs a slightly different approach.

In this guide, we’ll explain how to find the route the rain is taking, when a threshold seal can help and when you need to look at drainage or the surrounding ground. If you want a broader overview first, see our guide to keeping your garage dry in heavy rain.

Why heavy rain can catch you out after a dry summer

After weeks of dry weather, water coming into the garage can feel like a sudden new problem. In practice, the gap or drainage issue may have been there all along. The first heavy downpour simply makes it visible.

The Met Office provisionally recorded summer 2026 as the UK’s hottest on record, with a mean temperature of 16.5°C. That gives this autumn’s checks some timely context, although a national weather record won’t tell you why your own garage is leaking. You can read the Met Office’s summer report for the detail.

For your garage, the useful question is what happens to rain once it lands outside. Does it drain away, collect in front of the door or travel across the drive towards it? Leaves and debris in a drain can add to the problem, so check those before assuming you need a different seal.

You don’t need to wait for another storm to start looking. A dry day is a much better time to inspect the opening and plan any work. Our guide to preparing your garage for more extreme weather covers the longer-term considerations.

First, find where the water is getting in

Before you buy anything, look for the first point where water appears. A puddle in the middle of the floor tells you where the water has collected, but it may have entered at a corner and travelled across the concrete.

If it’s safe to watch from inside during ordinary rain, check the bottom of the door, both corners and the frame above. Look at the walls too. Water coming through the building itself won’t be stopped by sealing the door.

You can also use a gentle flow from a hose to check one small area at a time, with someone inside watching. Start at floor level and work upwards. Avoid a pressure washer or a strong jet: you’re trying to trace a leak, not force water through the opening. A hose check is useful, but it won’t reproduce every storm or flooding condition.

Treat these as clues, rather than a diagnosis from a single wet patch. More than one route can be involved. While you’re checking, leave air bricks and ventilation openings clear.

What if the garage floor is uneven?

Close the door and look along the bottom edge. If it meets the floor at both ends but leaves daylight in the middle, the concrete may dip beneath the door. You may also find that the gap is larger on one side than the other.

Measure the gap in several places, including any obvious low spots. One measurement at the centre can miss the part that needs the most attention.

A flexible PVC threshold can accommodate some unevenness. The important thing is that it makes contact with the door and has a continuous sealed bond beneath it. If water can travel under the threshold, the raised section above it won’t solve the leak.

For a deeper dip, crumbling concrete or substantial cracking, get the floor assessed before fitting. Adhesive isn’t a substitute for repairing an unsound surface, and simply choosing a taller seal can create problems where the door already sits close to the floor.

Check the outside level as well. If paving or a step sits above the garage floor and directs rain towards the opening, the better answer may involve changing that level or intercepting the water outside. Our guide to sealing an uneven garage door explains the options in more detail.

Don’t overlook the sides and corners

A threshold closes the route along the floor. It doesn’t automatically close every gap around the door, which is why a garage can still have wet corners after a new threshold has been fitted.

On an up-and-over door, inspect the existing seals around the sides and top. If they’ve cracked, pulled away or stopped making contact, wind-driven rain may get past them. Suitable replacement seals can help close those gaps. See our guide to sealing the top and sides of a garage door.

Sectional and roller doors can need a different check. Where the door sits behind the opening, look at the space between the wall and each side track. An open route here can let water bypass the end of a threshold. GaraDry foam side blocks are designed to close these spaces where required.

Check the whole route from wall to track to threshold. Even a small unsealed space at the end can leave somewhere for water to pass. Follow the instructions for your door and seal combination, and keep the door’s moving parts clear.

When you need to look at drainage

There’s a difference between rain blowing through a gap and a driveway delivering a steady flow of water to the door. A threshold can help with water at the opening, but it doesn’t give that water somewhere else to go.

If water regularly pools outside, start by checking any existing channels and gullies for leaves, silt and other blockages. If clearing them doesn’t solve it, or the drive slopes towards the garage with no drainage in place, ask a suitable contractor to assess the levels and drainage.

A channel drain across the entrance may intercept run-off before it reaches the door, provided it has a suitable outlet and is correctly designed. Changing the fall of the ground can also help in some situations. These are decisions to make for the property, rather than fixes to guess at from the doorway.

A garage door threshold is a barrier at the floor line. Water can still enter if it rises above the barrier, passes around its ends or finds another route through the building. A taller threshold doesn’t remove those limits. Our comparison of garage seals and drains explains how the two approaches can work together.

If your property has flooded or you’re concerned about wider flood risk, look beyond the garage door. In England, the GOV.UK flood preparation guide explains how to check risk, sign up for warnings and make a flood plan. It also links to the separate guidance for Scotland, Wales and Northern Ireland. Consider property protection and insurance as part of that plan.

Choosing the right GaraDry seal

Start with the opening you have. Measure the width, then measure the gap under the closed door at several points and note the largest reading. Consider how much water collects outside too. Those details are more useful than choosing a height because it sounds suitable for autumn weather.

Our domestic PVC thresholds are available in 15mm, 20mm, 25mm, 30mm, 40mm and 50mm heights. Check the fit and the required level of protection together. A taller option needs enough room to sit correctly while allowing the door to close and operate normally.

You’ll find the current lengths, prices and kit contents on the product pages. For help narrowing down the options, use our threshold buying guide. If you’re unsure, contact us with your measurements and photos of the door, floor and side tracks. That gives us a much clearer picture of what you’re trying to seal.

Fitting it properly matters as much as choosing it

A suitable threshold still needs a sound surface and careful fitting. Before you start, read the instructions for your particular product. Different profiles and door arrangements can need different details.

For our domestic PVC thresholds, the basic checks are straightforward: clean away dirt, oil and loose material; position the threshold behind the closed door; and check that the door closes, locks and operates correctly before bonding it. Dusty or powdery concrete needs sealing first. Loose concrete and gravel are unsuitable surfaces.

Use GaraDry Adhesive and Sealant as directed. The bond needs to close the route underneath the threshold as well as hold it in place. Check the ends and any side blocks for remaining gaps.

The recommended application temperature is 5°C to 35°C. Keep the adhesive at room temperature before use, and allow 24 hours after fitting before driving over the threshold or testing it with water. Pick a suitable weather window so you can prepare and fit it without rushing.

For heavier vehicles or frequent traffic, check product suitability before buying. Our commercial threshold range may be more appropriate. You can also find the wider seasonal checks in our autumn and winter weatherproofing guide.

Frequently asked questions

Why does rain come under my garage door?

Usually there’s a gap between the door and the floor, but water can also pass around the corners or collect where the ground slopes towards the opening. Find the entry point first. That tells you whether to focus on a threshold, the door edges, the floor or drainage.

Will a threshold seal stop my garage flooding?

A correctly fitted threshold can help stop rainwater entering at the bottom of the door. It won’t stop water that overtops it, bypasses it or enters through walls or the floor. If the property is at flood risk, consider drainage and wider flood protection as well.

What height threshold do I need?

Measure the gap beneath the closed door at several points and use the largest reading as your starting point. Then consider the water that collects outside and whether the chosen profile allows the door to close properly. If the floor is badly uneven, address that before relying on a taller seal.

Why is water still coming in at the corners?

Check the ends of the threshold, the door-edge seals and any open spaces beside the tracks. Water may be going around the seal rather than over it. Finding that route is more useful than replacing the threshold with a taller one straight away.

Can I fit a seal in cold weather?

For GaraDry Adhesive and Sealant, the recommended application range is 5°C to 35°C. Prepare a sound, clean surface and follow the fitting instructions. Allow 24 hours before driving over the threshold or testing with water, so choose a weather window that gives you time to do the job properly.