Do you need gravel under a concrete slab?

Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Excavate the soil to a depth of 8 inches, allowing 4 inches for the gravel base and 4 inches for the concrete slab.Click to see full answer. In this manner, what type of gravel goes under concrete?Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.One may also ask, what do you put under a concrete slab? Just scrape off the sod and topsoil and add gravel fill if needed. If you have clay or loam soil, you should remove enough to allow a 6- to 8-in. layer of compacted gravel under the new concrete. If you have to remove more than a few inches of dirt, consider renting a skid loader or hiring an excavator. Also, what is the best base for concrete slab? Subgrade and subbase are the foundation of a concrete slab and play critical role in its performance. According to the ACI Code, the subgrade is a compacted and improved natural soil or brought infill whereas subbase is a layer of gravel placed on the top of the subgrade.Can you pour concrete directly on dirt?Prepare the dirt before pouring concrete. If you are constructing a patio, shed or a sidewalk, the process often starts with pouring a solid concrete base to provide sturdy support. Home owners can accomplish the task themselves by pouring the concrete directly on the ground in the installation area.