Polished concrete is not a coating — it is the concrete itself, mechanically refined to a specified level of reflectivity. Every pass of the grinder removes surface material and refines the scratch pattern. Every subsequent grit removes the scratches left by the previous one. Done correctly on the right substrate, polished concrete in Toronto produces a floor that never needs recoating, resists most cleaning chemicals, and hardens progressively as the densifier reacts with calcium hydroxide in the slab. Done on the wrong substrate with the wrong equipment, you get an uneven sheen with visible grinding swirls that no amount of final polishing will fix.
The 6-Step Polishing Process
Every professional concrete polishing job follows the same sequence. Skipping steps produces visual defects in the finished surface that cannot be corrected without starting over.
- Rough grind — 50 grit (metal bond): Metal-bond diamond tooling removes surface laitance, existing coatings, and high spots. This pass sets the aggregate exposure level — cream (no aggregate), salt-and-pepper (partial), or full aggregate. The choice is made here and cannot be reversed later.
- Crack repair and patching: After the rough grind reveals the true surface condition, cracks are filled with semi-rigid polyurea or matching cement slurry, and spalls are patched. Repairs must cure fully before grinding continues — typically 1–2 hours for polyurea.
- Densifier application: Lithium or sodium silicate densifier is applied to the ground surface. The silicate reacts with calcium hydroxide in the concrete to form calcium silicate hydrate (CSH) — the same compound that makes concrete hard. This hardens the surface, reduces porosity, and improves the final sheen. Densifier must penetrate and dry fully (minimum 4–6 hours, ideally overnight) before fine polishing begins.
- Fine grind — 100 → 200 → 400 grit (transition to resin bond): Resin-bond diamond pads take over after the densifier. Each pass removes the previous scratch pattern. At 400 grit the surface is uniformly matte with no visible grinding marks.
- Polishing — 800 → 1500 → 3000 grit (resin bond): Higher-grit passes develop reflectivity. At 800 grit you have a Class 1 matte finish. At 1500 grit, Class 2 satin. At 3000 grit, Class 3 semi-gloss approaching Class 4 mirror.
- Guard coat: A penetrating densifying guard (silica or lithium-based) is applied after the final polish pass. The guard resists staining, reduces water absorption, and maintains the sheen level. It is not a coating — it penetrates rather than sitting on the surface.
Full Grit Progression Table
| Grit | Bond Type | Purpose | Sheen Output |
|---|---|---|---|
| 50 | Metal | Remove laitance, set aggregate exposure | None — raw cut |
| 100 | Metal / Hybrid | Remove 50-grit scratches | Flat matte |
| 200 | Resin | Refine surface, apply densifier before this pass or after | Flat matte |
| 400 | Resin | Remove 200-grit scratches, uniform matte achieved | Flat matte |
| 800 | Resin | Begin developing reflectivity | Class 1 Matte |
| 1500 | Resin | Low-angle reflection develops | Class 2 Satin |
| 3000 | Resin | Sharp reflection, guard coat applied | Class 3–4 Mirror |
Why you can't skip grits: Each grit leaves a scratch pattern of a specific depth. The next grit is sized to remove exactly those scratches — and no more. Jumping from 200 to 1500 leaves the 200-grit scratch pattern visible under the high sheen, producing a hazy or cloudy finish that looks worse than a proper matte.
4 Sheen Classes: What They Look Like and What They Cost
Class 1
Matte
Stop at 800 grit
$3–$5 / sqft
No reflectivity. Diffuse, flat finish. Light scatters rather than reflects. Best for industrial spaces, back-of-house, and utility areas where durability matters more than aesthetics.
Class 2
Satin
Stop at 1500 grit
$5–$7 / sqft
Low-angle reflection visible but no clear image. Subtle sheen that reads as "polished" without the full mirror effect. Popular in retail, offices, and residential spaces.
Class 3
Semi-Gloss
1500–3000 grit + guard
$7–$10 / sqft
Distorted reflection visible. Lights are visible but not sharp. High-end retail standard, restaurant dining rooms, hotel lobbies, and prestige commercial spaces.
Class 4
Mirror
Full 3000 grit + guard
$10–$15 / sqft
Clear, sharp reflection of overhead fixtures and objects. The most demanding specification — requires a sound, flat slab with good cream quality or controlled aggregate exposure. Showrooms, flagship retail, and prestige interiors.
Substrate: The Factor Most Contractors Don't Discuss Up Front
Slab Age
Minimum 28-day cure before polishing. 90 days preferred — concrete reaches approximately 90% of its design strength by then, and the densifier reaction is more effective on a harder surface. Polishing green concrete produces a soft, porous surface that won't hold a Class 3 or 4 sheen.
Aggregate Exposure
Cream finish (no aggregate) requires the flattest, most consistent slab. Salt-and-pepper (partial aggregate) is more forgiving of surface variation. Full aggregate exposure (paste removed to reveal stone) is the most forgiving option and is favoured in commercial projects where the slab has been heavily contaminated or patched.
Equipment Matters
A Husqvarna PG 820 or HTC Superfloor planetary grinder puts even downward pressure across a 500mm+ head diameter — critical for consistent aggregate exposure and flat scratch patterns. An angle grinder or single-disc machine leaves swirl marks and uneven exposure that show through the final polish. Ask what equipment your contractor uses before signing.
Polished Concrete vs. Epoxy: Which for Toronto Spaces?
| Factor | Polished Concrete | Epoxy Flooring |
|---|---|---|
| Material added | None — integral finish | Polymer coating over slab |
| Recoating required | No (re-polish if worn) | Every 5–15 yrs |
| Colour options | Slab colour + dyes | Unlimited |
| Imperfect slab tolerance | Low (cracks visible) | High (coats hide defects) |
| Chemical resistance | Good (densified) | Excellent (100% solids) |
| UV stability | Excellent | Requires polyaspartic top |
| Typical cost (Toronto) | $3–$15/sqft | $4–$15/sqft |
| Best for | Retail, office, restaurants, lobbies | Garages, warehouses, industrial |
Frequently Asked Questions
How much does concrete polishing cost in Toronto?
2026 Toronto pricing by sheen class: Class 1 matte $3–$5/sqft, Class 2 satin $5–$7/sqft, Class 3 semi-gloss $7–$10/sqft, Class 4 mirror $10–$15/sqft. Pricing includes the full grit progression, densifier, and guard coat. Crack repair, coating removal, or leveling is quoted separately. Minimum project size for commercial pricing is typically 500 sqft; smaller areas carry a mobilization premium.
What are the different sheen levels for polished concrete?
Four classes: Class 1 (matte, 800-grit stop) has no reflectivity. Class 2 (satin, 1500-grit stop) shows low-angle reflection but no clear image. Class 3 (semi-gloss, 1500–3000 grit + guard) shows distorted reflection. Class 4 (mirror, full 3000-grit + guard) produces a clear, sharp reflection. Each class requires all preceding grit steps — there are no shortcuts.
How long does concrete polishing take?
A Class 2 satin finish on a sound 1,000 sqft slab typically takes 2–3 days including densifier cure time. A Class 4 mirror finish on the same area takes 4–5 days. Variables extending the timeline: removing existing coatings (add 0.5–1 day), significant crack repair, aggregate exposure requiring extra coarse passes, and flatness issues. Densifier must cure overnight before fine polishing begins.
Can any concrete slab be polished?
Not every slab is suitable. Concrete must have cured for minimum 28 days (90 days preferred). The surface must be structurally sound — polishing cannot fix a weak or delaminating slab. Heavy contamination, widespread cracking, or soft concrete (low PSI) limits achievable sheen class. A cream finish requires a flatter, cleaner slab than a full-aggregate-exposure finish, which is more forgiving of surface variation.
What is the difference between polished concrete and epoxy flooring?
Polished concrete is a mechanical process — the concrete itself is ground and refined. No coating is added; the finish is integral to the slab. It never needs recoating, just periodic re-polishing if traffic wears the sheen. Epoxy applies a polymer coating over the slab, offering more colour options, better chemical resistance, and higher tolerance for imperfect substrates. Common split: polished concrete in public-facing retail and restaurant areas; epoxy in back-of-house, industrial, and garage applications.