What Do You Put Down Before Concrete? The Essential Foundations for a Successful Project

When beginning a new construction project that involves pouring concrete, it’s essential to establish a strong and stable foundation. The success of the project relies heavily on what’s put down before the concrete is poured. One crucial step is to create a base of gravel, which serves multiple purposes. Firstly, it helps prevent erosion, ensuring that the slab remains intact and undamaged over time. Secondly, the gravel base aids in preventing any settling of the concrete, which could lead to cracks or uneven surfaces. In order to create a solid base, it’s important to pour concrete sand to fill the gaps within the gravel, ensuring a smooth and level surface. To further ensure stability, a tamper or plate compactor can be used to flatten the gravel base, creating an even and compacted surface. If necessary, additional layers of gravel can be added and compacted until a 4-inch base is achieved. By following these crucial steps and establishing a solid foundation, your concrete project is set up for success.

What Is the Best Base for Concrete Slab?

Another reason is that gravel provides stability and support for the concrete slab. It helps to distribute the weight of the concrete evenly and prevents any shifting or cracking. Before laying down the gravel base, it’s important to properly level out the soil. This ensures a flat and compacted surface for the concrete to lay on.

To begin, remove any vegetation or debris from the area where the concrete will be poured. This includes grass, weeds, rocks, and any other loose materials. Next, use a shovel or grading rake to level the soil. You may need to remove excess soil or add more to ensure an even surface. It’s important to have a slight slope away from any structures, such as a house or garage, to promote proper drainage.

The recommended thickness for the gravel base is 4 inches. This will provide enough support and stability for the concrete slab. Spread the gravel evenly across the entire area and use a compactor or hand tamper to firmly pack it down. This will help to prevent any settling or shifting of the gravel.

After the gravel base is in place, it’s important to check the slope and levelness again. Make any necessary adjustments before proceeding with pouring the concrete. It’s also important to consider adding reinforcement, such as wire mesh or rebar, depending on the size and intended use of the concrete slab. This will help prevent cracking and provide added strength.

The best base for a concrete slab or driveway is a properly leveled soil followed by a well-compacted gravel base. This combination provides good drainage, stability, and support for the concrete. By taking the time to properly prepare the base, you can ensure a successful and long-lasting concrete project.

How to Properly Level and Compact a Gravel Base for a Concrete Slab

  • Measure and mark the area where the concrete slab will be poured.
  • Remove any vegetation, obstacles, or debris from the area.
  • Dig out the topsoil to a depth of at least 6 inches.
  • Compact the soil using a plate compactor or hand tamper.
  • Add a layer of geotextile fabric to prevent weed growth.
  • Add a layer of crushed stone or gravel to the area.
  • Spread the gravel evenly and compact it using a plate compactor.
  • Check the level of the gravel base using a long straight board and a level.
  • Add or remove gravel as needed to achieve a level surface.
  • Mist the gravel base with water to settle it.
  • Compact the gravel base again to ensure proper compaction.
  • Add a layer of sand on top of the gravel base for additional leveling.
  • Rake the sand to create an even surface.
  • Check the level of the sand using a straight board and a level.
  • Add or remove sand as needed to achieve a level surface.

There are several options available for moisture barriers under concrete, but the most widely used and recommended is polyethylene (poly) plastic sheeting. With thickness options like 10 mil or 15 mil, All Americover Vapor Barriers offer the ideal solution. These barriers are made of high-quality virgin polyolefin resins and are available in different mil thicknesses, including 10 mil, 15 mil, and 20 mil.

What Is the Best Moisture Barrier Under Concrete?

When it comes to laying a concrete foundation, one of the most important elements to consider is the moisture barrier that goes underneath the concrete. The moisture barrier serves as a protective layer that prevents water and moisture from seeping up through the ground and into the concrete slab. Without a proper moisture barrier, the concrete can become weakened and damaged over time.

The most commonly used vapor barrier under concrete slabs is polyethylene (poly) plastic sheeting with a thickness of 10 mil or 15 mil. This type of material is known for it’s excellent moisture resistance and durability.

All Americover Vapor Barriers are composed of virgin polyolefin resins, ensuring high-quality performance and longevity. These vapor barriers are available in various thicknesses, including 10 mil, 15 mil, and 20 mil. The thickness you choose depends on the specific requirements of your project, such as the moisture conditions of the soil and the expected load on the concrete slab.

Source: Creating a Moisture & Vapor Barrier Under Concrete Slab


This involves the careful placement of a layer of gravel to prevent erosion and settling. Following these foundational steps will yield a durable and reliable concrete structure that will stand the test of time.

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