Four common polishing mistakes that will wreck your new floor

Here are four reasons why you should do your research when selecting the concrete polisher to create your dream floor. If you don’t, here’s what might happen to you.

1. The floor delivered isn’t anything like what you asked for.

You told the concrete polisher exactly what you wanted your floor to look like and he’s gone “Yep, yep, I can do that, no problem”. But when the final floor is unveiled, it’s nothing like your instructions. What happened?

There are a couple of issues here, but the main one is that the concrete polisher has not managed the client’s expectations of what is possible with the surface laid by the concreter.

Every concrete surface is different and some concrete companies do a better job of concrete placement and finishing than others. What the concrete polisher can achieve will be affected by how the concrete is screeded to get it level, it compaction during placement, the concreter’s system and sequence for finishing the concrete, its hardness when dry, and uneven surface levels (e.g. a 4mm variation in the finished floor level between high and low points).

(For the best polishing results, a good concrete polisher will want to be involved before the concrete floor is even poured. A check of the specifications and a discussion with the concreter will make it much clearer what is expected in the finished concrete.)

Once the concrete is laid, the concrete polisher will closely examine the surface looking for imperfections that may cause him problems. He’ll listen carefully to what you want and then he’ll tell you honestly what he can achieve with the surface.

For example, a light random stone exposure has become popular of late. This requires the polisher to grind off only 1-2mm of the concrete surface. However, if your floor is not perfectly flat – say it has a 4mm difference between high and low points – the polisher has to grind down just past the lowest point to get a platform for a good polishing surface.

So your desired light random stone exposure of 1-2 mm automatically becomes a 5mm grind, which is full stone exposure. There is a huge visual difference between light and full stone exposure.

Another example is the final gloss on the floor. The client’s expectation of a high-gloss finish may be different to what the polisher can actually achieve. Sixty gloss units on a glossmeter rates as high gloss, but many polishers will struggle to reach this.

As the client who is investing in an expensive product, you should always view your potential polisher’s previous work so that you understand what he can deliver. Every tradesman in every trade delivers to a different standard.

2. Your floor has noticeable ridges in it.

The concrete surface may not have been laid perfectly flat, but the concrete polisher then fails to grind the floor flat. Or the floor was flat and the polisher grinds it badly and makes it uneven.

This mistake will really damage the look of your floor. It might have ridges or the grinding pattern may be visible in places. The final sheen or gloss on the floor will also be uneven because light will refract off the floor at different angles and only look shiny in parts.

3. In light, your finished floor looks like it is full of holes.

When a polisher grinds off the concrete surface to expose the aggregate within it, he removes the smooth trowelled surface that hides all the bubbles and imperfections in the concrete below.

As part of the polishing system, all those bubbles and imperfections need to be refilled by a suitable ‘grout’. I grout a floor three times as part of my GeoshineTM concrete polishing system using a clear acrylic polymer that fills in the holes and cracks.

If a floor is poorly grouted, the floor’s voids and imperfections will not all be filled. This means that when light refracts off the final surface, instead of an even, perfect sheen or gloss your floor will look like an Aero chocolate bar – full of holes.

4. Your floor chips when something hard is dropped on it or shows marks when heavy furniture is moved.

As part of the polishing system, densifying chemicals (such as potassium, lithium and colloidal silicate) are applied to the ground surface to increase the hardness of the concrete. The densifiers react with unconverted calcium hydroxide, turning it into much harder calcium silicate hydrate. The aim in increasing the floor’s hardness is to make the final surface much more durable and highly resistant to wear, abrasion, chipping and cracking.

Skimping on densifier is a cost-cutting measure. Premium quality off-the-shelf densifiers are expensive and you can use a lot of it, depending on the size of the floor. Cheap densifiers are generally a weaker formulation.

A floor that has not had enough densifier applied may still look good after polishing, but it won’t have reached its maximum hardness. It will be much more likely to wear, abrade and chip.

Another possible effect of insufficient densifying is ‘leopard spots’. In a gloss surface, the exposed aggregate looks really shiny and the surrounding concrete matrix looks flat and dull.

Most concrete polishers will apply one type of densifier 2-3 times. In our GeoshineTM system, we apply densifier nine times and use three different densifying chemicals. I personally make Geocrete’s densifier chemicals from the raw ingredients and they are strong! It also means I can make bulk premium chemicals at an economical price.

Other polishers would probably say I overdo the densifying, but I create the hardest, most durable floors that can carry a brilliant, even high gloss for many years. I can achieve this consistently in my floors, and I guarantee residential floors for 10 years and commercial floors for seven. It’s likely they’ll last a lot longer than that, too.

These common mistakes are costly to fix – if they can be fixed at all. The expert polisher you’ll have to call in will need to start the floor again from scratch. I’ve done it several times and achieved excellent results, but you really don’t want any of these mistakes made on your floor.

For tips on how to choose a polisher, see my blog ‘Five tips on how to choose a concrete polisher’.

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