Quick Answer

Use a PCD (polycrystalline diamond) cup wheel for thick, flexible residues like thinset, mastic, glue and epoxy, then switch to a segmented diamond cup wheel to level the screed afterward. Grind in slow, overlapping passes with light pressure, keep the wheel flat against the slab, and run a HEPA dust extractor. The combination of the right bond, shallow cuts and constant dust control removes grout and adhesive without grooving the slab or exposing unwanted aggregate.

Match the Wheel to the Residue

Not every grinding wheel behaves the same on old grout and adhesive:

• PCD cup wheels — shatter and scrape off thick thinset, mastic, glue and epoxy in seconds. The 6-PCD PCD cup wheel is the standard choice for floor prep and will chew through most tile adhesive without loading up.
• Segmented diamond cup wheels — once the sticky film is gone, a 6-segment diamond cup wheel levels the surface and opens the concrete without digging in.
• Double-row cup wheels — a double-row cup wheel removes material faster but cuts more aggressively, so use it only when the slab can tolerate a lighter finishing cut.

Start with PCD for the adhesive, finish with diamond segments. Skipping the PCD step means your diamond wheel glazes over on the sticky residue and stops cutting altogether.

Step-by-Step Removal Process

1. Test a corner first. Grind one square meter to judge how aggressive the wheel is and how deep each pass cuts.
2. Knock out loose grout by hand where tiles are already missing; this stops the wheel from snagging on free joints.
3. Make 2–3 shallow passes per area instead of one deep pass. Let the wheel cut; pushing down forces segments into the slab.
4. Overlap each pass by a third so no unground strip remains between tracks.
5. Change direction between passes — perpendicular, then parallel — to flatten the surface evenly.
6. Switch to the finishing diamond wheel once the adhesive film is removed.

How Not to Damage the Slab

The slab is damaged by technique, not by the wheel itself:

• Keep the wheel flat. Tilting it digs a crescent groove at the edge of the disc.
• Use light pressure. A cup wheel removes material by the weight of the grinder, not by your arm pushing down.
• Stay at the RPM printed on the wheel. Too slow overheats and glazes segments; too fast gouges soft concrete.
• Never dwell in one spot. Keep moving — a parked wheel grinds a visible dip in seconds.
• On polished or exposed-aggregate slabs, start with a finer finishing wheel rather than a coarse PCD disc.

Dust Control and Safety

Grout and adhesive removal generates large amounts of crystalline silica dust. Fit the angle grinder with a vacuum shroud connected to a HEPA extractor, and wear a P2/N95 respirator, safety glasses and hearing protection. Where wet work is permitted, light wet grinding suppresses dust almost completely — just be prepared to collect the slurry and let the slab dry before coating.

Frequently Asked Questions

Q: Can I remove grout between tiles without removing the tiles?

A: Yes. A PCD or diamond cup wheel fitted in a grout-remover setup grinds out grout joints between intact tiles. Keep the wheel on the joint line only, and use a guard so the disc does not scratch the adjacent tile faces.

Q: Will grinding reach underfloor heating pipes?

A: Shallow removal of adhesive (usually less than 1–2 mm) rarely reaches embedded pipes, but check the floor plans first. If pipes sit at shallow depth, work in very shallow passes and mark the pipe routes on the floor.

Q: Why does my diamond wheel load up on sticky glue?

A: Diamond segments glaze because the metal bond cannot ablate against soft adhesive. That is exactly what PCD tooling is for: it scrapes the glue off cleanly. Follow up with diamond segments only for leveling.

Q: Is an angle grinder enough, or do I need a floor grinder?

A: For small patches, an angle grinder with a cup wheel and shroud works. For whole rooms, a walk-behind floor grinder removes adhesive faster, flatter and with far less operator fatigue.

Conclusion

Removing grout and old tile adhesive is a two-step job: PCD for the sticky film, diamond segments for leveling. Light pressure, overlapping passes and a HEPA vacuum keep the slab flat and the air safe. Need the right wheels for your machine? Write to [email protected] — JOY TECH manufactures PCD and diamond cup wheels for angle grinders and floor machines, backed by SGS and BV audited quality.