How to Handle Water Coming Up Through Your Garage Floor After It Rains (+ Prevention Tips)

Bry'Ana Arvie
Written by Bry'Ana Arvie
Updated June 7, 2022
Car in attached garage
Photo: Kirill Gorlov / Adobe Stock

Water flooding your garage is never fun—here’s what you can do to tackle the problem

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After heavy rain, the last thing you want to deal with is a flooded garage. Whether your area is experiencing flash floods or you just live downhill during a downpour, the garage is one of the first areas where water accumulates. Here’s what to do if you spot signs of flooding, plus how to keep it from happening in the future.

1. 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 setup 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.

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 surface waterproofing the outside of the foundation wall.

Garage 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 damages to your garage roof, it may have holes or loose boards, or shingles, resulting in rainwater leaking on your floor. 

The best solution to fix this problem is to hire a roofing repair pro near you for the task. The cost to replace your garage roof is $1,000 to $2,000,depending on size and roofing material.  

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 common during the rainy seasons like spring and fall because of high humidity levels. When your garage is cooler than the 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’re noticing 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. 

2. Stop Water From Getting Into Your Garage

Inside view of a 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.

Here are a few quick fixes you can implement to solve this problem:

  • Apply weather stripping to the joints at the outside edge

  • Install a rubber seal strip on the bottom of the door

  • Install a grouted sill at the door bottom seal to act as a dam

  • Check insulation and add as needed

  • Use a dehumidifier

  • Install at least one fan to increase air circulation 

In some cases, it’s not possible to fix the source of a leak right away. In this case, it’s a good idea to remove the water as fast as possible, then contact a concrete flooring professional near you to help you stop future flooding.

3. Dry Out Your Garage

If a significant amount of water comes up through your garage floor when it rains, 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 and water damage from setting in. In some cases, it may be helpful to use a rotating fan to improve air circulation and dry things out faster.

4. Prevent Future Leaks

No matter what the source of your leak is, you should 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 update your current one. Newer garage doors are more insulated and offer better weather stripping 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 floor discoloration and stains.

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