Subgrade and Base Are Different
Subgrade means the soil beneath the work. A base is a specified layer placed above that soil. The preparation and materials required depend on the project; not every slab has the same build-up.
Consistent Support Matters
Soft areas, disturbed soil, and changes in support deserve attention before placement. Site preparation should follow the project requirements. A thicker slab alone is not a complete answer to unsuitable ground.
Plan for Drainage
Ask how surface water will move, where it will go, and whether the concrete affects existing drainage. Texas soils vary. Expansive clay and changes in moisture may require site-specific evaluation.
Plan support and drainage before choosing the finished surface.
Further Reading
NRMCA — CIP 4: Cracking Concrete SurfacesGeneral education for project planning. Your site's conditions and project requirements determine the construction details.