How to Fix a Flooded Garage After a Storm (+ Prevention Tips)

Identify the Source of the Leak

The most important thing you can do to deal with flooding in your garage is to figure out the source of the leak. This step can help you determine what to do next to prevent flooding in the future.

Gutter Downspouts

Sometimes flooding is caused by a buildup of water from gutter downspouts that did not carry the water away from the house. This causes water to leak through the foundation and into the garage. To prevent flooding caused by gutter downspouts, you should direct downspouts away from the foundation with a proper drainage slope and clean your gutters twice per year.

High Groundwater

High groundwater or seepage can also cause flooding. To prevent this from happening, you’ll need to accelerate drainage away from your home. You also might want to consider installing a French drain or waterproofing the outside of the foundation wall.

Roof Leaking

While the water’s on your floor, don’t count your roof out just yet. If you live in an older home or have recently sustained damage to your roof, it may have holes or loose boards or shingles, resulting in rainwater leaking onto your floor. 

The best solution to fix this problem is to hire a roof repair pro near you for the task. The cost to repair your roof is between $380 and $1,800, depending on your roofing material and the extent of the damage.  

Garage Located at the Bottom of a Slope

Another problem you can run into is rainwater coming into your garage because of poor landscape sloping. When your garage is at the bottom of a slope, any water will naturally travel downhill, which in this case, is your garage. 

To combat this, you’ll need to direct water away from your garage, whether through changes to your landscaping or adding a drain.

Concrete Slab Cracks

Water can also get into your garage through cracks in your concrete slab. If the ground underneath your home is wet, which is common during rainfalls, it absorbs the water like a sponge and releases it through cracks in your concrete. 

If your home has a vapor barrier installed underneath it, this typically isn’t a problem like in newer homes. But if your home doesn’t have one or you have an older build, this can potentially be the issue. If you notice any cracks, address them right away to prevent the issue from getting worse.

High Humidity 

Condensation can occur throughout the year, but it’s more common during the rainy seasons, like spring and fall, because of high humidity levels. When your garage is cooler than outdoor temperatures, it can result in your garage floor sweating. And this issue can be made worse because of poor ventilation, which doesn’t allow the humidity levels to lower enough for the sweating to stop. 

If you notice high levels of humidity, adding a dehumidifier to your space can be a good fix.

Garage Door Leaking

Direct rainfall can cause dampness and flooding in your garage. In some cases, water can come through joints in the garage door or between the door and the side frame. 

In this case, you’ll want to add additional weather stripping or even consider getting a new garage door if the problem is severe enough. 

Stop Water From Getting Into Your Garage

Photo: Konstantin L / Adobe Stock

If there’s a clear culprit for garage flooding, you should take steps to fix the problem. The strategy you need to stop flooding depends on the source of the leak and the structure of your garage.

Apply Weatherstripping to the Joints at the Outside Edge

Garage doors need weather stripping, but it doesn’t last forever. Weatherstripping seals the sides and top of the garage door. Be sure to install proper weatherstripping to keep water from seeping into the garage. Also, inspect it often because if it wears out, it will no longer be effective. 

Install a Rubber Seal at the Bottom of the Door

The bottom of the garage door invites water into your garage without a rubber seal. The long rubber strip is flexible enough to compress when the garage door is closed, creating a seal that prevents water from entering the garage.

Discuss Your Landscaping Options

If your garage is the lowest point of your home, the water will naturally drain there. If your garage is the catch-all for your landscaping drainage, talk to a landscaper about changing the slope to protect your garage.

Add a Waterproof Veneer

Next to the garage door, your garage walls pose a threat for water accumulation if it has a way in, such as through cracks. Adding a waterproof veneer seals the barrier so water cannot enter the garage through the walls.

Keep Gutters Clean

Clogged gutters don’t allow water to flow away from the home and instead cause water accumulation. While clogged gutters themselves may not risk the integrity of your garage, a combination of clogged gutters, a bad slope, and excessive water could be a recipe for disaster.

Get a Foundation Inspection

Regularly have your foundation inspected for cracks. If the foundation cracks, water can accumulate between the cracks. If the water accumulates too much, it can cause sinking problems within the concrete, putting the garage at further risk of flooding. Catching and fixing cracks early can prevent these issues.

Add Sandbags

If you know you have a water accumulation problem, try a temporary fix until you can permanently fix the underlying problem. Sandbags can force the water to go in a specific direction—away from your garage. 

Dry Out Your Garage

Similarly to what you would do if your basement floods from rain, you’ll likely need to dry out your garage and any possessions or equipment you store there. If possible, it’s a good idea to air out your garage to help things dry.

You should also be sure to mop up any water that has leaked into your garage to prevent mold from setting in. You may also need a few extra pieces of equipment to dry things out faster.

Use a Dehumidifier

As soon as you know the garage flooded, add a dehumidifier to help dry out the area. You can rent commercial-sized dehumidifiers from your local hardware store if you don't have one. Run it for three days to a week to thoroughly dry the area.

Use Fans

While drying out the garage, fans can be extremely helpful. Use them with a dehumidifier to keep the air circulating and encourage all areas to dry quickly. Like the dehumidifier, consider keeping the fans in the garage for three days to a week.

Check Insulation and Add as Needed

If the garage flooded, chances are the drywall and insulation were affected. Check the drywall for water stains or signs of water infiltration. If the drywall is soft to the touch, chances are the insulation was also affected. Remove all affected areas and replace them as needed.

Prevent Future Leaks

No matter what the source of your leak is, you’ll definitely want to take steps to prevent it from happening again.

Direct Water Away From the House

Your biggest priority should be making sure any water is directed away from your foundation. For example, you should be sure to direct roof runoff away from your home and toward a proper drainage area. 

If a sloped driveway is causing water to seep into your garage, you may need to install an open-top driveway drain or a "speed bump" on the drive itself to divert the water off to the side where it will drain away from the house.

Install Ditching and Drainage

In some cases, you may want to install ditching to help prevent flooding. You should install ditching at least 5 feet from the foundation and preferably at least 10 feet away in high water table areas. Another solution is to place a French drain a couple of feet into the ground to provide drainage.

Fill in Cracks

If you notice that your garage floor is wet because groundwater is coming from underneath your concrete, fill in those cracks. Without a way for the water to escape through the concrete, it won’t come up and flood your floor. So, your first step is to clean the cracks, then use a concrete patch compound to fill in each one you find throughout your garage.

Install a New Garage Door

Sometimes, the best solution to prevent water from coming into your garage after it rains is to upgrade your garage door. Newer garage doors are more insulated and offer better weatherstripping than older ones, allowing your garage to stand a fighting chance against flooding. The average cost to install a garage door is $1,200.  

Protect Your Garage Floor

To protect your garage floor, it’s a good idea to cover it with a garage floor sealant or coating. These coatings can help to prevent water damage and protect your floor while also adding aesthetic appeal and preventing garage concrete discoloration and stains.

Bry'Ana Arvie contributed to this piece.