A monolithic slab is a type of foundation that is poured in one application, also known as an all-in-one pour or single pour foundation. It is a popular foundation type in the United States due to its cheap installation cost and long-term durability. Monolithic slabs are comprised of a single pour cement application, with thicker areas of concrete around the perimeter and areas supporting load-bearing walls. The thicker perimeter edges help provide more reinforcement and stability, as a good portion of the home’s load will be redirected outward. Monolithic slabs tend to be 6-8 inches thick and are typically the same thickness across their whole depth.

The term "monolithic" comes from the Greek word "monolithos," meaning "made of one stone". Monolithic slabs are energy-efficient, requiring less energy to heat and cool a home than a stem wall or post-and-pad. They are also fast to lay, as they can be poured much faster than other foundations. However, monolithic slabs may not be suitable for all climates, as they are best suited for areas that dont freeze during the winter or get too hot during the summer months.

In summary, a monolithic slab is a type of foundation that is poured in one application, with thicker areas of concrete around the perimeter and areas supporting load-bearing walls. It is a popular foundation type in the United States due to its cheap installation cost and long-term durability. Monolithic slabs are energy-efficient and fast to lay, but may not be suitable for all climates.