Sand concrete garage slab to prep for epoxy coating and remove lai...

Use power sanding to save time on large flats, then switch to hand sanding for edges and final control. This sequence shows how to sand a concrete garage slab to prep for epoxy coating and remove laitance through 400–1500 grit without leaving random deep scratches.

Consistency beats speed: finish each grit step completely before you move up.

Why Sanding Matters

Sanding removes defects and creates a uniform surface profile for the next step. If the scratch pattern is inconsistent, you’ll see it later—especially after paint, clear coat, or polishing. A controlled progression keeps the finish predictable.

Recommended Tools

• Sandpaper sheets (hand control + edges)
• Optional: orbital sander for large flats
• Sanding block / pad
• Vacuum/dust collection
• Microfiber cloths
• Masking tape

Recommended Grit Sequence

Use this sequence in order and inspect between steps.

• 400 grit: keep motion steady; finish edges by hand.
• 600 grit: keep motion steady; finish edges by hand.
• 800 grit: keep motion steady; finish edges by hand.
• 1000 grit: keep motion steady; finish edges by hand.
• 1500 grit: keep motion steady; finish edges by hand.

Step-by-Step

1. Mask and protect. Tape off trim/edges and cover areas you don’t want scuffed.
2. Clean the surface. Remove oils and dust so the abrasive cuts evenly.
3. Start with 400 grit. Use even strokes. Keep a block flat on large surfaces; use a flexible pad on curves.
4. Inspect under raking light. Wipe clean and confirm one consistent scratch pattern.
5. Step up through 600 and 800 grit. Slightly change direction between grits and reduce pressure.
6. Refine with 1000 grit. Keep strokes steady—avoid stopping in one spot.
7. Finish with 1500 grit. This sets your final surface profile for prep for epoxy coating and remove laitance.
8. Hand-finish edges. Sand edges and corners last with reduced pressure to avoid cut-through.
9. Final cleanup. Vacuum/brush, then wipe with a clean cloth before the next stage.

Special Cases

Concrete dust is fine and abrasive; use proper respiratory protection and vacuum often.

Pro Tips

• Swap to fresh sheets when cutting slows; clogged paper can leave random scratches.
• Reduce pressure as grits get finer.
• Wipe between grits for accurate inspection.
• Use a block on flats to avoid finger grooves.

Aftercare

• Remove dust from seams, corners, and crevices before coating.
• If wet sanded, dry fully before primer/paint/clear coat.
• Store unused sheets flat and dry.
• Discard heavily loaded sheets so old finish doesn’t re-scratch the surface.

FAQs

• How do I avoid swirl marks? Use consistent strokes, keep pressure light, and fully remove the previous scratch pattern before moving up.
• Why do I still see deep lines at the end? Usually because the first grit step wasn’t completed or a grit was skipped.
• Should I sand edges the same as flats? No—edges cut faster. Sand them last with reduced pressure.

Watch & Learn

Here are the exact grits referenced in this sequence so you can match the workflow: 100 grit (pack of 10), 180 grit (pack of 10), 220 grit (pack of 10).

• 100 Grit Sandpaper Sheets — Pack of 10
• 180 Grit Sandpaper Sheets — Pack of 10
• 220 Grit Sandpaper Sheets — Pack of 10

Complete each grit step, inspect under angled light, and keep pressure consistent. That’s the simplest way to get a finish-ready surface.