Replacement reveals the support below
A garage floor that has settled, cracked widely or separated from the threshold may have conditions below it that a surface treatment cannot correct. Removal allows the underlying material and any localized voids to be assessed.
Doors and thresholds
The vehicle-door opening, overhead-door seal, service doors and connection to the driveway create fixed edges. The slab profile needs to work between them without directing water farther into the garage.
Use and preparation
Vehicle loads, storage and the building configuration inform the slab plan. Preparation is selected for actual conditions rather than a universal recipe, and utilities or drains require coordination before placement.