Subgrade & Base Prep Checklist

Many slab problems are caused by base and drainage—not concrete thickness. Use this checklist to improve performance on slabs-on-grade.

1) Subgrade condition

• Remove organic material, topsoil, and soft spots.
• Moisture-condition soils before compaction (avoid pumping mud).
• Proof-roll if possible to find weak areas.

2) Compaction

• Compact in lifts; avoid thick lifts that won’t densify.
• Target a firm, uniform surface; avoid loose edges.
• If you don’t have compaction testing, at minimum use repeatable equipment and procedure.

3) Base material

• Use a well-graded granular base where practical.
• Typical base ranges from 4–8 inches depending on soils and loads.
• Keep base uniform thickness; feathering creates weak transitions.

4) Drainage

• Keep water away from slab edges; slope grades away.
• Manage downspouts and runoff so water does not saturate the base.
• In freeze/thaw climates, drainage becomes even more important.

5) Joints (plan before you pour)

• Place control joints to manage shrinkage cracking.
• Keep panel sizes reasonable; avoid re-entrant corners.
• Cut joints early enough to be effective.