Should Garage Floors Be Sloped? What You Need To Know

Garages are seen as a point between the interior and exterior of the house. They provide a final barrier between the house and the street in care of any issues like flooding. But you may wonder if garage floors should be sloped or not. 

Garage floors should be sloped to match building regulations. The sloping of garage floors is to encourage drainage and prevent water from entering the house. However, the slope’s degree may vary from one area to another, based on rain and snow levels.

In this article, I’ll go into why garage floors need to be sloped, what the regulations say about slope degrees, how to measure the slope of your garage floor, and how you can achieve a sloped floor in your garage. 

Why Are Garage Floors Sloped?

Garage floors are sloped to encourage water or other liquids away from the house and towards existing drainage systems or onto the main street and its drains. The slope is usually a necessary part of the building regulations of the area. 

In most houses, water tanks, boilers, and washing machines are located in the garage, requiring extensive plumbing and a system to drain away water. In areas that get regular rain, the slope is more important to ensure that water doesn’t flow into the house. 

Unlike the main house building, which is typically built higher than the road, the garage is almost level with the road and can get flooded easily if the floors aren’t sloped to drain water. 

Degree of Slope for Garage Floor

Typically the degree of the garage floor’s slope is very gentle and hardly perceptible. Most people don’t know about the slope unless they’re familiar with building codes and requirements or want to redo their garage. 

There’s no standard degree of slope for the garage floors. The amount of sloping required under the building code varies from area to area for multiple reasons. Typically, the slope’s degree on garage floors is greater in areas prone to flooding or ones that receive heavy rainfall or snow. 

Within a region, this degree might be different depending on the garage size. Larger rooms might need a more frequent sloping at lower levels to ensure that the slopes themselves aren’t dramatic or uncomfortable. 

Most guidelines for garage floors are listed to indicate how many inches the floor should fall after each foot of flooring. 

According to the national code, the minimum recommended slope for garage floors is a fall of  ⅛ of an inch (0.32 cm) after every foot of the floor.

Floor Drains and General Slopes

In some areas, homeowners prefer to install floor drains instead of just having the floor slope towards the main entrance of the vehicle. The floor drains still require a slope but towards the installed drain rather than any exterior drain. 

Slopes for floor drains are slightly more complicated to install since the floor must be higher along the edges of the garage and slope down from all four sides towards the floor drain. 

According to building codes, the installed drain must be connected to the area’s main drainage and sanitary system.

Some cities and towns require homeowners to install floor drain instead of a more general slope to the main entry if the garage contains appliances like water heaters, boilers, washing machines, etc. This requirement is because appliances might generate more wastewater than the road drains are equipped to handle.

Measuring Garage Floor Slopes

If you’re trying to install a bench or table in your garage, you’ll need to consider the garage floor’s slope to ensure that whatever you install is straight and not parallel to the floor. 

To measure the slope, you need a string level, also known as a line level. Attach one end of the level to the garage wall opposite the main entryway. This end of the garage will be the highest point of the slope since the garage floor will slope away from this wall towards the main entrance. 

Reel out the string till you reach the opening of your garage, attach the level to the string, and pull tightly till the string becomes taut.. 

Once the bubble on the level is exactly between the two center lines, hold a protractor against the garage floor. Then move the plumb bob or plummet, which is the weight suspended from the string level so that its string is in line with the level’s string, and the point crosses the top of the protractor.

That degree mark is the degree of slope of your garage floor. 

You can use this degree to calculate exactly how much you’ll have to compensate for when you’re adding anything to your garage that needs to sit straight. 

Installing Garage Floor Slopes

You can install a slope into your garage in two ways:

• Calculate the slope, and pour the concrete slab on top of the sublevel at varying thicknesses according to the slope’s degree. This method is used if you’re not redoing your flooring entirely and simply want to add a slope to your garage floor. 
• Excavate the sublevel floor with your desired slope and pour concrete. 

If you’re excavating the sublevel floor to the desired slope, then the person pouring concrete must be careful to pour the concrete parallel to the excavation. The concrete shouldn’t be poured to level because that’ll render all the excavator’s work meaningless and result in a floor with no slope. 

Final Thoughts

Garage floors are required to have slopes by the rule of building codes, which vary from area to area. These slopes must direct water towards a drainage system or the main entrance of the vehicle.

If you need to measure the degree of slope on your garage floor, you can do so with a string level. To add slope to your garage floor, you can either add the slope by pouring the concrete at different thicknesses or excavate the sublevel to the desired slope and pour concrete parallelly. 

Recommended Reading:

• How To Frame a Wall on a Sloped Floor (5 Steps)
• Should You Put A Dehumidifier In Your Garage? (Condensation)
• How to Seal a Garage Door Correctly [Top, Bottom, & Sides]