A slab is considered a single concrete layer that is several inches thick. A slab is poured thicker around the edges in order to create a footing, where reinforcing rods are placed to strengthen this thick edge. The slab itself normally rests on a crushed gravel bed, which helps to improve drainage. Monolithic means it was poured all at once. This type of slab is cast in place as one single piece that includes footers. This is different than slabs that are supported by foundation walls that are poured separately.
Monolithic slabs are best used in buildings that are found in warm climates. For cold climate structures, they only work well for farm buildings. Ultimately, there are a handful of requirements needed in order to construct monolithic slabs successfully. First, the soil underneath the slab must not contain organic matter and must be compacted. If the topsoil itself is scraped away then the soil that is undistributed will be compacted. All of this soil must be well drained so that water does not undercut the slab itself.
Local building codes designate how deep and wide the trench for the slab should be. In warmer climates, the trench may only need to be a foot deep and a foot wide, while in places that have frost in colder months, the trench may need to be as deep as 2 feet. Building codes also mention the type and the placement of the reinforcements used in this type of slab. Also, the most common concrete used is 3,000 psi that is at least 4 inches thick with the top slab being at least 6 inches above the soil, which should slope away from the slab.