Polished concrete floors are durable, low-maintenance, and visually striking — but not every slab is suitable for polishing. Before any grinding or densifying starts, you need to assess the condition, thickness, hardness, and history of the floor. This guide walks through how to evaluate whether a concrete slab can be polished, and when it’s smarter to resurface or start fresh.
A polishable slab must be structurally sound. Use a core drill or hammer test to confirm it’s at least 75–100mm thick with no major voids or delamination. For upper floors or suspended slabs, check load ratings and flex — movement can lead to surface cracking during polishing. Slabs poured thin or with poor compaction often fail under mechanical polishing equipment.
Hairline cracks can be repaired before polishing — but large, uneven, or shifting cracks are red flags. Spalled areas, delamination, and poor aggregate distribution also affect whether the slab can be polished attractively. Check around expansion joints, corners, and old patch repairs for stability. In some cases, damaged areas can be repaired with epoxy filler or micro toppings, but extensive issues may require resurfacing.
Soft or dusty concrete doesn’t polish well — the surface must be dense enough to take mechanical grinding. A Mohs hardness kit or rebound hammer can help test. Slabs below 3000 psi tend to polish poorly unless treated with hardeners. If the surface dusts easily under foot traffic or flakes when scratched, you’ll likely need densifiers or resurfacing. Dense, well-cured slabs offer the best polishing base.
Existing coatings must be completely removed before polishing. Check for paint, tile glue, epoxy, or sealers by doing a water drop test — if water beads, there’s a barrier. Mechanical removal (grinding) is possible, but heavy coatings add time and cost. Some surface stains, like oil or grease, can also penetrate deep enough to shadow through the polish — especially in older garage or warehouse slabs.
Polishing exposes surface inconsistencies. Use a long straightedge or laser level to check for humps, waves, or dips. Minor undulations can be corrected during grinding — but uneven slabs may show through in the final finish. In retail or residential settings, this can affect the aesthetics. Slabs with poor formwork, cold joints, or extreme camber may not be good polish candidates without heavy prep.
The finish you're aiming for determines how much grinding is needed. A cream polish shows only the paste — while a full aggregate polish requires deep grinding. If the slab has uneven aggregate, patchy mix, or inconsistent pouring, it may not produce an attractive result. Talk with the client or end-user about expectations — in some cases, a micro-topping or overlay may be better than trying to polish a poor-quality slab.
If in doubt — get a pro involved. An experienced concrete polishing contractor can inspect and test the slab to determine whether it’s viable. They’ll assess slab age, previous use, contaminants, moisture risk, and the practical grind depth needed. In many cases, a polishable slab just needs prep work — but if structural or cosmetic issues are too great, they’ll recommend alternatives like overlays or resurfacing.
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