How to Stop Water Leaking Under an Up and Over Garage Door

An up and over garage door is one of the most common types fitted to homes across the UK. It is reliable, easy to use, and cost effective, but like all garage doors it is not without its weaknesses. One of the most frequent complaints from homeowners is water leaking in beneath the door.

Even small amounts of water can create significant problems. Damp patches damage stored items, encourage mould and mildew, and make the garage unpleasant to use. Persistent leaks can also undermine flooring and create costly maintenance issues. Fortunately, there are several effective ways to stop water seeping under an up and over garage door.

This article explains why water leaks happen, the most practical solutions, the types of seals available, and the steps you can take to keep your garage dry and protected.

Why Water Leaks Under Up and Over Doors

The design of an up and over door means it rarely sits completely flush against the ground. The door pivots upwards and outwards before sliding back into the garage, and this movement requires clearance. Even when the door is shut, small gaps usually remain at the base.

These gaps may seem minor but can let in rainwater during storms or when wind drives water against the door. The problem is worse if the garage floor is uneven, cracked, or sloped. If your driveway slopes towards the garage, water naturally flows to the entrance, increasing the risk of leaks.

Worn or damaged seals make the issue worse. Rubber hardens, cracks, or flattens over time, reducing its ability to block water.

Problems Caused by Water Ingress

Water leaking into your garage is more than just a nuisance. It can cause:

• Damp and mould growth, which damages walls and stored items
• Rust and corrosion on vehicles, tools, and equipment
• Increased humidity, making the garage uncomfortable to use
• Structural damage if water seeps into concrete or wooden floors
• Attraction of pests such as rodents and insects seeking moisture

Preventing leaks not only improves comfort but also protects your property from costly repairs.

Solutions to Stop Water Leaks

There are several practical ways to stop water leaking under an up and over garage door. The right solution depends on the cause of the problem and the condition of your garage.

Install a Bottom Seal

A bottom seal is the first line of defence. These rubber strips attach to the underside of the door and compress against the floor when the door closes. They block small gaps and stop water seeping through.

For larger gaps or uneven floors, thicker bulb shaped seals are best, as they compress more deeply.

Fit a Threshold Seal

Threshold seals are fixed to the garage floor with adhesive. Made from heavy duty rubber or PVC, they create a raised ridge across the width of the entrance. When the door closes, it presses against this ridge, creating a watertight barrier.

Threshold seals are particularly effective for driveways that slope towards the garage, as they divert surface water away before it can reach the interior.

Add Side and Top Seals

While most leaks occur at the base, water can also enter around the sides or top of the door during heavy rain. Adding weatherstripping around the frame provides extra protection and improves insulation at the same time.

Level or Repair the Floor

If the garage floor is cracked or uneven, water will always find its way in. Resurfacing or levelling the floor creates a smoother base for seals to work against. Even patching small cracks can make a big difference.

Improve Drainage

Good drainage is essential if your driveway slopes towards the garage. Installing a channel drain in front of the door diverts rainwater away before it reaches the threshold. This is one of the most reliable long term solutions for persistent water ingress.

Raise the Door Frame Slightly

In extreme cases where water levels are consistently high, raising the frame or adding a small step at the entrance can help. This requires more extensive work but provides lasting protection.

Step by Step: Fitting a Threshold Seal

Because threshold seals are one of the most effective solutions, here is a detailed guide to fitting one.

1. Measure accurately
   Use a steel tape measure to record the width of the garage opening at floor level. Select a threshold seal of matching length and appropriate height for the gap you need to close.
2. Clean the floor
   Sweep and wash thoroughly to remove dirt, grease, and debris. Allow the surface to dry completely, as adhesive will not bond to damp concrete.
3. Mark the position
   Place the threshold in position and close the garage door gently to confirm alignment. Mark the outline on the floor with pencil or chalk.
4. Apply adhesive
   Apply the adhesive in a continuous bead along the marked outline. A caulking gun is usually the easiest method.
5. Press the threshold into place
   Press down firmly along the full length, ensuring good contact. Close the door again to check the fit.
6. Allow curing time
   Leave the adhesive to cure for 12 to 24 hours before driving over the seal or exposing it to water.

This process usually takes under two hours, with additional time required for curing.

Maintenance of Seals

Fitted seals need regular care to remain effective.

• Clean every few months with mild soap and water to remove dirt and grit
• Apply a silicone based spray to rubber seals to keep them flexible
• Inspect for cracks, flattening, or detachment twice a year
• Replace seals promptly if damaged

With proper maintenance, seals typically last three to seven years, depending on conditions.

Common Mistakes to Avoid

Several mistakes reduce the effectiveness of water protection.

Cutting the seal too short leaves permanent gaps. Always cut slightly long and trim carefully.

Fitting on dirty or damp surfaces weakens adhesive bonds, leading to early failure. Thorough cleaning is essential.

Choosing the wrong size seal is another error. A flat strip may not block larger gaps, while an excessively thick seal may prevent the door from closing properly.

Neglecting drainage is also a mistake. Even the best seal will struggle if large volumes of water constantly flow towards the garage.

Benefits Beyond Stopping Water

Stopping leaks has other advantages too.

It improves comfort, making the garage more usable as a workspace, gym, or storage area.

It protects belongings, reducing the risk of damp or mould damage.

It supports energy efficiency by blocking draughts, keeping adjoining rooms warmer in winter.

It prevents pest infestations, as rodents and insects are less likely to enter a dry, well sealed space.

Professional vs DIY Installation

Most seals can be fitted by homeowners with basic tools. Threshold kits and bottom strips are designed for DIY use.

However, professional installation may be worthwhile for uneven floors, motorised doors, or garages with persistent water problems. A professional can recommend the best combination of seals and drainage improvements.

Conclusion

Water leaking under an up and over garage door is a common but solvable problem. The main solutions include fitting a bottom seal, installing a threshold strip, adding side and top weatherstripping, repairing the floor, and improving drainage.

For most households, a combination of a bottom seal and threshold provides immediate relief. For more serious issues, drainage and levelling may be required.

By measuring carefully, cleaning surfaces thoroughly, and maintaining seals regularly, you can keep your garage dry, clean, and comfortable year round.

For homeowners, the message is clear. A small investment of time and effort in sealing your garage door prevents costly repairs, protects your belongings, and ensures your home remains safe and efficient.