How to grind and polish a concrete floor

A polished concrete floor is a sequence: grind with metal-bond diamonds, fill holes and cracks, densify, polish up the resin grits, then seal and burnish. For each step: what to fit, what to watch for and when to move on, with the grinder choice at the end. Tooling is in Floor Grinders and Polishers and Diamond Polishing and Maintenance Tools.

Check the slab before you load the grinder. The hardness of the floor decides the metal bond: hard floor, soft bond; soft floor, hard bond. A bond that suits the floor wears back at the right speed, so fresh diamond keeps cutting.

Paint, epoxy or adhesive on top comes off first, with polycrystalline diamond (PCD) tooling. PCD is graded by tool geometry, not by a grit number. The PCD tools are in Metal Bond Diamond Tools.

A planetary grinder stops 100 to 300 mm short of every wall, so the margin is hand-held work: an angle grinder and a variable-speed polisher (see the machine table below). No walk-behind machine does stairs, so stairs are hand-held work too. New concrete needs 28 days to cure before the sealer goes on (Seal and burnish, below).

Grinding concrete releases respirable crystalline silica (RCS). The limit is 0.1 mg per cubic metre over 8 hours, set in the HSA Code of Practice 2026 under S.I. No. 122 of 2024 as amended.

Wear a respirator (RPE) while grinding: a disposable FFP3, or a half or full face mask with a P3 filter, as the HSA lists. Add eye and ear protection, and goggles and gloves when you handle the densifier and sealer.

Dry grinding gives the better finish on the floor. It needs an M-class dust extractor on every pass, from Industrial Vacuums and Dust Extractors, and H-class over old coatings of unknown make-up.

Wet grinding trades dust for slurry. The slurry is a slip hazard and should not go down the drain.

Fit Easy Fit metal segments in the bond that matches the floor. They come in six bonds from extra-extra-soft floor (XXSF) to extra-extra-hard floor (XXHF). Grind at 30, then 80; fill cracks and holes (next section); then grind at 140. The segments also come in 16 grit, which is for prep contractors laying another system on top. Every planetary grinder in the fleet takes the same Easy Fit tooling on its own carrier plate.

Pick the look before the first pass: cream, salt and pepper, or exposed aggregate. The early metal passes set how much aggregate shows, so the depth of the first grind is the decision.

A grit is done when the scratch from the grit before it has been removed across the whole floor. Then change to the next grit.

Watch the segments. If they turn smooth and shiny while the machine slides and the dust stops, the bond is glazing: it is too hard for the floor, so go softer. If they wear down in hours, the bond is too soft: go harder.

Metal ends at 140. Optional ceramic transitional pucks, 30 to 200 grit, bridge the jump to resin, and follow the same rule: hard floor, soft bond. The soft bond and super hard bond ceramic pucks come in 30, 50, 100 and 200; the Ceramic Bond puck in 100 and 200.

Fill after the 80 grit metal pass, then finish the metal at 140.

Pores and fine cracks: Hypergrinder HG-100 Grout Filler. Mix it about 1:1 with clean dust from the 80 grit pass, never the first pass, so it takes the colour of the floor. It stays flexible, so the next grits grind it without breaking out.

UltraLit Hard Premium is a lithium densifier. Its lithium reacts with the concrete to form calcium silicate hydrate in the top layer, which hardens the surface and cuts dusting.

It goes on part-way through the resin passes (next section), after the 120 or the 220 pass. Both are common, and both sit inside the TDS window of 100 to 400, before the high grits. Clean off the dust and let the floor dry before you spray.

Drying typically takes 1 hour at most; the full reaction can take up to two weeks. Apply only when it will stay above 2 degrees C for at least 4 hours. Wash any overspray off metal, glass, wood, paint and brick with clean water straight away.

Joints to be filled after densifying must be cleaned out first, with a saw or a grinder fitted with a wire wheel.

Swap the metal for 75 mm resin pucks on the same Easy Fit stations. Condor Green steps 60, 120, 220, 400, 800, 1800 and 3000; Jumper Universal adds 30 and ends at 3500.

Stop after the 120 or the 220 to densify (previous section). Climb one grit at a time. Skip a step and the fine puck cannot clear the coarse scratch; it polishes into the shine. Drop back a grit and climb evenly.

Keep the machine moving. Parked, or run dry too long, the resin glazes and stops refining. Edges and corners take a variable-speed hand-held polisher with 100 mm velcro pads, from Hand-held Polishers.

The last grit sets the finish. On the Condor Green ladder, 220 reads matt, 400 satin and 800 gloss; 1800 and 3000 are high gloss. For a glossy finish, UltraLit specifies progressively finer grits from 800 to 3000.

UltraLit Gloss Plus suits most polished floors: shops, offices, showrooms. UltraLit Gloss Shield is for floors that take punishment: warehouses, forklift routes, food areas. Both are for interior use; protect them from freezing.

The floor must be at 200 to 400 grit or finer, clean and dry, and new concrete must have cured for 28 days. Apply only when it will stay above 2 degrees C for at least 4 hours.

Spray a thin first coat with a low-pressure sprayer, no puddles, and spread it with a microfibre pad wetted with the sealer, at 25 to 40 square metres per litre. Once dry, burnish with a high-speed burnisher on pads without diamonds, such as the HY1500C burnisher. The pads must heat the floor to 32 degrees C.

Apply a second coat at 40 to 80 square metres per litre and burnish again, and a third at the same rate if needed. The floor is ready for traffic once dry, typically within 1 hour. Keep water off for at least 72 hours; full water and stain resistance takes 7 days.

Aftercare is light. A dry dust mop or a microfibre pad keeps the shine, and a microfibre mop and water is all a wash needs. There is no stripping and no build-up: when you want a fresh coat of sealer, it goes straight on.

Two things to know at the start. The first wet clean waits 7 days, until the sealer reaches full water and stain resistance. Acidic cleaners (pH below 7) are out, and spills are best wiped up when you see them, as some acids stain if left.

A cleaning machine is optional, for a deep clean. An auto scrubber improves the shine, and SupraShine diamond pads with water keep the gloss: wet on a scrubber or single-disc machine, just damp from 800 grit up on a burnisher.

ICRI Technical Guideline 310.2R-2013 grades prepared concrete from CSP 1, minimal roughness, to CSP 10, very rough. ICRI Table 7.2 lists grinding at CSP 1 to 2.

On ICRI's reference chips, CSP 1 is acid-etched and near smooth, CSP 2 is ground, the profile a metal-bond grind leaves, and CSP 3 is a light shot blast, past a grinder's reach.

If the floor takes a coating instead of a polish, follow the CSP on the coating's datasheet. ICRI's bands are CSP 1 to 2 for sealers up to 76 microns thick and CSP 3 to 5 for high-build coatings of 0.25 to 1.0 mm, which is shot blaster or scarifier work.

Irish contractors quote about EUR 90 to 150 per square metre for a polished floor, so EUR 9,000 to 15,000 for 100 square metres. A full kit from us starts at about EUR 2,300 inc VAT. Doing it yourself can save up to about EUR 12,700 on 100 square metres. Contractor rates are from PMAC and Selfbuild Ireland; the kit figure is Concrete Care's, 2026-10-22.

On 100 square metres, allow up to a week across all the grits. Add the waits: the densifier and each sealer coat dry within about 1 hour, no water goes on for 72 hours, and full water and stain resistance takes 7 days.