Flat sawing is the most commonly used diamond cutting method. It is typically used to cut horizontal flat surfaces such as floors, bridge decks, and pavements. Also called slab saws, flat saws feature a diamond blade that is mounted on a walk-behind machine requiring only one operator. Flat saws are typically used to provide expansion joints, remove damaged pavement sections, clean and repair random cracks for repair, and remove concrete sections for demolition purposes.

As with the diamond wall saw blade, a flat saw blade consists of a circular steel core with diamond segments attached to the periphery. The blade is mounted vertically on the spindle of the flat saw. The flat saw is pushed or propelled along a flat surface while the diamond blade makes the vertical cut to the required depth. Flat saws are typically powered by gasoline or diesel engines, electric or hydraulic sources. Flat saw blades can range from 12 - 54 inches (305 mm - 1.4 m) in diameter and can cut up to 24 inches (610 mm) in depth.