Quick Answer

A 30-year-old cracked floor can usually be polished, but it needs repair before grinding. Fill active cracks with epoxy, test for moisture, remove any old sealer with PCD, then grind from 30 grit upward. Skip the crack repair and you will see every crack through the polish.

Inspect First

• Active cracks need structural evaluation before polishing.
• Spalled or hollow areas need patching.
• Moisture test (calcium chloride or relative humidity). Old slabs often have high moisture.
• Old sealer or wax must come off before diamond grinding.

Step by Step

1. Repair cracks with low-viscosity epoxy. Let cure 24 hours.
2. Patch spalls with polymer mortar.
3. Remove old sealer with PCD. Our Piranha PCD prep tooling handles most acrylic and epoxy sealers.
4. Start at 30 grit with metal-bond shoes like our R3 round-segment shoes. Do not start finer on a neglected floor.
5. Step through 30 → 60 → 120 → 200, then transition to resin.

What to Expect

Old floors have trowel marks, uneven wear from foot traffic, and sometimes oil stains. The first couple of coarse passes will look rough; the floor evens out by 120 grit. Browse concrete grinding discs category for the full grit sequence.

Frequently Asked Questions

Q: Can I polish over old tile adhesive?

No. Remove it with PCD first, then grind.

Q: How do I know if the slab is too far gone?

If you can lift pieces of concrete or the slab is moving under load, structural repair is needed before polishing.

Q: Does polishing hide cracks?

No, it makes them more visible. Repair first.

Conclusion

Old floors polish well after a proper repair cycle. PCD for old sealer, 30 grit to start, and patience. contact JOY TECH for a tooling list sized to your floor area.