Why You Need Gravel Under Concrete

Posted on: July 23, 2022

Do you need gravel under concrete? Yes, it is necessary to have gravel underneath concrete for a few reasons. First, it provides a firm foundation for the concrete, preventing water from splashing up. Secondly, it’s easy to compact, so you can pour concrete without worrying about it getting wet. But why do you need gravel underneath concrete? Read on to discover the benefits of gravel underneath concrete. Listed below are several reasons why you need gravel under concrete.

Compressed gravel provides a solid foundation for concrete

The first step in setting a slab is to compact the gravel, which acts as a capillary break. Water cannot move up the gravel because the spaces between each stone are too large. This process can reduce the amount of concrete needed for the slab and will also ensure that it won’t shift. Then, the soil is graded so that the center of the excavation site is slightly higher than the sides, which will allow water to drain properly.

When choosing a type of gravel, 3/4″ to one inch is ideal. In North America, this type of gravel is sometimes referred to as “driveway gravel” or “57 gravel.” Larger rocks are difficult to compact, too porous for some concrete types, and hard to level. Moreover, large rocks may make rigid foam installation difficult or even break it. Ultimately, choose gravel based on its size and application.

It prevents water from splashing up

A splash block is an important safety feature for concrete foundations. These structures channel fast-flowing water away from the foundation so it will not damage it. Downspouts create fast-flowing water that is not linear enough to enter the ground. Splash blocks channel the water in one direction away from the foundation to prevent damage. They are an inexpensive, easy-to-install option that prevents water from splashing up under concrete.

It is easy to compact

The best way to compact gravel under a concrete slab is by wetting the gravel. Wetting the gravel makes smaller pieces sink into the subgrade. Otherwise, they can shift and cause the concrete to sink and crack. You should leave 2-4 inches (5.1-10.2 cm) of space in between each piece of gravel when compacting it. Also, make sure to compact the gravel on a level surface. Even if it appears flat and level, the gravel can be crooked or bumpy.

Compaction is essential when installing a concrete slab. It prevents the soil from eroding. Also, it prevents water from collecting underneath the slab, which may eventually cause cracks. Concrete absorbs moisture, and a pooling of water beneath it will cause cracks in the slab. By compacting the gravel under the slab, you will prevent any leaks in the concrete slab. The best way to compact gravel under concrete is to follow these steps.

It is hard to pour

Before starting to pour gravel under concrete, it is necessary to determine where you plan to set your slab. Generally, you should place four stakes at each corner to indicate the corners of the slab. Next, determine the slope of the ground. If the ground is not level, you may have to fill in the low part with soil or create a wooden box. When finished, you can pour gravel under the concrete and check for levelness.

If you do not want to purchase soil or gravel, it is possible to dig out the area to an eight-inch depth and grade it. This will help water drain properly. You should use gravel that has a good drainage rate. You can find this information at your local building department or from the American Concrete Institute. You can also inquire with your local street department to determine the standards for gravel and earth for driveways. In either case, it is vital to consult your materials supplier to find out what is the best subbase material for your project.