Can a slab on grade be a floating slab?

Answer 1

In laymen's terms, yes. Many people use the terms Slab-on-grade & Floating Slab interchangeably.

However, architects, engineers, and construction workers may have a more refined interpretation. Most commonly, a Slab-on-grade construction refers to a foundation in which the a concrete slab (also most commonly thickened at the perimeter) rest directly on grade (aka ground). Where as a Floating Slab foundation refers to a concrete slab resting directly on the grade independently placed within a stem wall (aka foundation wall), which extends down to the depth of the local frost line, running around the entire perimeter. The walls of the building/structure are then built upon this "stem wall". This latter type of construction creates a 'heat bubble' so that the floor is not as subject to the expansion due to frost and secures the structures walls by being supported below the frost line.