How to Prevent Garage From Flooding & Installing Drains


Garages can have flooding and water damage for many reasons. Maybe the garage is missing a drain, or something like gutters or driveway was built wrong during construction. Avoiding water damage is essential, so your belongings don’t suffer. Nobody wants to see ruined items. You avoid many building-related costly problems and possible mold in the long run when you keep the water out and the garage inside dry. 

Installing a floor drain, New weather sealing on the garage door, fixing the roof, walls, and gutters. Installing French drainage along the driveway and taking preventive measures during storms are the general ways to prevent the garage from flooding.

In this article, we look at how to remedy the situation if your garage has constant water and flooding problems.

Common Causes of Garage Flooding

Sewage Flooding

Sewage drainage pipes can clog from dirt or too much water in the system, and leaks can happen underneath and seep into the garage

Read why the garage smells here

Burst Water Pipes

Freshwater pipes can burst from pressure or freezing and can leak into your garage from the ground below or if the lines go thru the garage walls. 

Weather-Related

Storms, hurricanes, and heavy rainfalls cause flooding and overflowing water. Most water systems just can’t handle that much water in a short time frame. 

No Floor Drains and Broken Weather-Sealing in the Garage

Some garages don’t have any floor drains, and if water gets in, it will be a problem. Retrofitting the concrete slab with a trench drain or bell trap drain is a good idea if your garage regularly floods with water. Or the floor is regularly wet and needs to be dried. 

The drains will save you a lot of time and trouble. The garage floor drain is also helpful if you wash things inside the garage. With drains cleaning the floor becomes easy. 

The garage door has a weather seal at the bottom and around the door(paid link). It keeps the rainwater and bugs out. Check the seal regularly and replace broken sections or get an expert to fix it. The bottom seal especially wears out and needs to be changed periodically. Changing the seals is cheap. 

Read all about garage doors here

Seal Garage Water Entry Points 

Roof and Walls

Check the walls and roof for cracks and holes or get an expert to assess the situation. If your roof is leaky, it’s better to get it fixed or replaced to avoid significant water damage to the whole house. A waterproof veneer can be added to the garage walls to add water resistance to existing walls. 

Read how to finish garage walls here.

Garage Door and Floor Seals

Garage doors have weather seals that deteriorate over time in the bottom of the door and around the door. These should be replaced from time to time to keep the door at least rainwater tight. A broken weather seal at the bottom of the door is most of the time the problem when your garage has water all over the floor after heavy rain. 

Replacing the weather seal is cheap and fast, and even an expert installation doesn’t cost many bucks. So make sure this is the first place you check and fix. 

The garage foundation should also be inspected for cracks and damage that could cause freshwater lines or sewage pipes to burst. 

Garage Gutters

Check and clean the gutters yearly and make sure the builder has not cut corners with the size of gutters and you have a large enough gutter above the garage door. During heavy rain, look that the gutters don’t overflow and the water is directed long enough distance away with the downspouts from the garage door and your house foundation. 

Garage Driveway

Check your driveway that it slopes away from the garage door and that the perimeter soil around the driveway is not higher than the actual driveway. The rainwater should drain off the cement and not build ponds. If needed, alter the landscape to direct the rainwater away naturally and drive the water away from the house’s foundation and the driveway. 

Install a Garage Floor Drain

Building Codes and Regulations

You don’t have to be a contractor to install drains yourself, but it takes a DIY attitude and a little bit of know-how. You can rent the equipment needed.

Before starting your project, make sure you have all the permissions if required in your area. In most areas, you have to meet the local building and construction codes. There are also inspection requirements.

Some municipalities require special oil filtration or catch basins to filter the drainage pipe’s water to separate contaminants. The building code inspector may also check the drainage pipe for the proper pitch before pouring the concrete. 

Check Existing Utility Lines

Before starting your project, check the location of existing water or other utility lines in the concrete slab and on your property. Contact the local authorities and check your house construction plans. When you know where the utility lines are. Planning the project can start. 

  • In the United States and Canada, simply call 811. The utility company will come and mark the locations of existing underground lines. 
  • You are legally and financially responsible for any damages if you don’t call 811 and hit and break a utility line. 

Trench Drain

Trench drains are thin, long, and rectangular, with a removable grate on the top. Drains run into pipes and out of the garage. Trench drains come in different length sections that can be installed in the center of your garage or connected to run the entire garage length. 

These are more expensive than bell trap drains, and the install time is longer, but you have easier and faster cleaning time. 

Before pouring the concrete floor, you can install trench drains, which is more straightforward. Or retrofit them to the existing floor without drains. With existing floors, you have to dig the trench with heavy machinery. 

Floors with a proper pitch to the drain make the cleaning faster and easier. Trench drains with built-in pitch are easier to install in both cases. The concrete floor is sloped toward the trench. 

When retrofitting the drain to the floor, locating where the concrete slopes and water puddles naturally are the best place to put the drain. 

Trench drains can also be installed in front of the garage along the driveway. This is a good option if the driveway slopes towards the garage door. 

Check trench drains available at Amazon

Installing Trench Drain

  • Rent all the tools you need, like a concrete saw and jackhammer and any other equipment required. 
  • Cut a trench in the slab from the drain to where it will exit the building.
  • The trench should be about twice as wide as the pipe or trench and deep enough for the slope.
  • Make the trench deep enough at the place where the p-trap will be.
  • Dig connecting trench outside from edge of the concrete slab to where the pipe will exit to a final drainage point. 
  • Lay the pipe or the trench sections and keep the slope right.
  • Fill the trench with self-leveling concrete and finish the concrete if necessary. 

Bell Trap Drains

Bell trap drains are simpler than trench drains. Water runs into the drain and out through a pipe. Similar setup as your bathroom has. Bell trap drains come in a square and round variety. These are easy and fast to install. Drain sizes are usually 6, 9, and 12 inches. The drain material is usually PVC.

You can install bell trap drains before pouring the concrete floor, which is more straightforward, or retrofit them to the existing floor without drains. With existing floors, you have to dig a trench to the pipes with heavy machinery.

Floors with a proper pitch to the drain make the cleaning faster and easier. Bell trap drains are usually installed center of the garage bay and concrete sloped toward the drain from all sides. When retrofitting the drain to the floor, locating where the concrete slopes and water puddles naturally are the best place to put the drain. 

Check bell trap drains available at Amazon

Installing Bell Trap Drain

Where Does a Garage Floor Drain Go? 

Sometimes the drains are connected to the sewer, and other times lead to the curb and onto the storm drain. In Rural areas, the pipes can lead somewhere on the property away from the house. 

Garage floor drains go to the sewer, storm drain, or onto the property away from the house. Garage floor drains must have an outlet that leads water to the discharge point. If the water is contaminated, and oil filtration or catch basin system is required. 

French Drain or Trench Drain in the Garage Driveway

If your driveway and yard flood regularly, you could install a french drain and/or trench drain in the driveway in front of your garage. Or along the driveway to channel the water away from the garage, driveway, and house. 

A French drain is a ditch in the ground inset with a perforated pipe under a layer of gravel and landscaping textile. The textile prevents soil from clogging the holes in the pipe. French drain funnels excess ground and surface water away from the foundation and driveway. 

French drains are best utilized in soil that is frequently saturated from rainfall and prone to flooding.

Check landscaping drain pipes available at Amazon

Check Existing Utility Lines

Before starting your project, check the location of existing water or other utility lines in the concrete slab and on your property. Contact the local authorities and check your house construction plans. When you know where the utility lines are. Planning the project can start. 

  • In the United States and Canada, simply call 811. The utility company will come and mark the locations of existing underground lines. 
  • You are legally and financially responsible for any damages if you don’t call 811 and hit and break a utility line. 

Read all about garage safety hazards here

Installing French Drain

Read about trench drain in this section of the article. 

Storm Measures for a Garage 

During storms and hurricanes, it’s wise to take preventative actions to avoid water damage to your garage and household items you store. Installing barriers to direct most of the water away can save you from a lot of trouble and loss of property. 

Sandbags and Flood Barriers

Rent or purchase flood barriers and sandbags(paid link) if you live in an area with hurricanes and storms and direct most of the water away from the garage and house. Use these to build temporary dams. Sandbags weigh about 30-35 pounds.

Item Storing During Flooding

How Much Does It Cost to Install a Garage Floor Drain?

Installing drainage runs most homeowners between $1,932 and $5,782, with an average cost of $3,849. Small, simpler solutions could be as low as $500, and more complicated projects could get as expensive as $18,000. (source homeadvisor.com)

Type Cost With Labor & Materials
French$1,000 – $10,000 per 100 linear feet
Trench / Channel$3,000 – $9,000 per 100 linear feet
Underground Downspouts$200 – $2,000 per downspout
Yard Inlets$50 – $100 per inlet
Concrete Catch Basin/Storm$2,000 – $5,000 per basin
Plastic Catch Basin$200 – $500 per drain
(source homeadvisor.com)

Storm Drain Installation Cost

Storm drain channel systems cost $50 to $3,000. This system collects surface water from storms and then diverts it to a storm drain or dry well. You can purchase DIY kits or have a professional installation. They’re labor-intensive but require few tools. A handyman or landscaper usually install these systems. (source homeadvisor.com)

French Drain Cost

Exterior French drains cost $10 to $50 per linear foot on average, but you may pay up to $100 per linear foot for complex installs. Ranges depend on where you put them. For example, a surface drain in easy to access areas, like a yard, costs far less than excavating to the base of a foundation and adding a sump pump. (source homeadvisor.com)

Trench or Channel Drain Installation Cost Per Linear Foot

Trench or channel drains cost $30 to $100 per linear foot. Complex installs might run $150 per linear foot. The price of the trough or channel will depend on length and material. A steel driveway trench, for example, could be $100, where a concrete one could be $300.

Concrete driveways usually require breaking up the concrete, installing a surface drain, and repouring to seal it in. With proper concrete leveling, water flows through this drain and into a metal or concrete channel, directing the water away from your drive. Any type of system for driveways requires enough strength to withstand the weight of a parked car. (source homeadvisor.com)

Cost of Drainage Work

Labor to install drainage work costs $50 to $100 per hour. Most projects take between 12 and 72 hours total or 1.5 days to a week or more. You’ll usually have a crew of 2 or 3 people working on any given project. For any project that requires concrete or blockwork, you’ll want to budget extra time for demolition and reinstallation. (source homeadvisor.com)

Drainage Pipe Prices

Drainage pipes cost $1 to $5 per linear foot. You can purchase them without a fabric cover, with a fabric sock, and with a thick fabric and foam filtration layer. (source homeadvisor.com)

  • Drainage catch basin costs $30-$100 each.
  • Channel drain kits cost $10-$15 per linear foot.
  • Connectors and junctions cost $2-$10 each.

DIY Drainage Installation vs. Hire a Pro

You’ll find many DIY drainage kits on the market. They’re easy to install, require little background experience and few tools. These are a great option for some homeowners with a weekend to install them. However, if they’re not leveled correctly, they won’t solve your water issues. You also need a basic understanding of how and why you have drainage issues and how to correct them. A complete DIY job costs $100 to $2,000 total. (source homeadvisor.com)

However, if you don’t have the time or experience to install these yourself – or want the peace of mind that comes with a professional installation – hire a local drainage installation professional. They’ll address your drainage issues and stop any current damage from getting worse. (source homeadvisor.com)

What to Do if the Garage Has Flooded

If your garage floods, take the following steps after the flood. Keep in mind your garage now may be contaminated with sewage or chemicals left over from the floodwaters. Wear protective equipment like waterproof clothing and boots, gloves, and protective eyewear(paid link).

  • Turn of the power if you can access the fusebox safely. Contact expert if in doubt.
  • Check the whole garage for structural damage. Take pictures for the insurance company.
  • Look for cracks, sagging roof, wet insulation, and ruined wiring
  • Assess the damage to your personal property, which was stored in the garage.
  • Patch holes with tarps and boards if needed.
  • Get the insurance company to assess the damage on-site if necessary and permission to remove any leftover water and start fixing the damage.
  • Reduce moisture any way can. Circulate the air and use dehumidifiers. 
  • Mold and mildew start to grow after 24-48 hours after the water exposure. So wash items like clothes immediately and disinfect them and dry them.
  • 10% bleach solution can be used to disinfect surfaces and remove mold. 
  • Salvage and clean what you can. 

Read what is safe to store in the garage and what is not in here

Read how to clean the garage here

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