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Sanded or Un-sanded Grout on Dimensional Stone Floors

By: Mike Marsoun
NuLife Stone Care

I have noticed an alarming trade practice here in Australia which desperately needs to be addressed. The root of this problem is the same as in the US where you will find ceramic tile installers stepping into the area of natural stone tiles, which is a skill really more suited for a stonemason. Since the stone tiles are essentially the same size and shape as a typical ceramic floor tile, the reasoning is that laying could not be too different and one could use the same techniques. Nothing could be further from the truth. The density, porosity, stability, colour consistency, and size/thickness consistency is all very different in stone and for a proper installation all of these factors need to be considered. Where one could lay all ceramic tiles with certain setting materials and technique, this is not the case with natural stone.
From what I have seen this problem is wide spread and the seriousness threatens the stone industry itself. Stone installations are not holding up over time and it is the material, rather than on the faulty installation practices, that are copping the blame.
One problem I have seen in a large majority of floors I have looked at for restoration is the incorrect use of floor grout. The problem goes like this: for some strange reason here in Australia the materials companies put grout in two classifications, “Wall Grout” and “Floor Grout”. The “Wall Grout” is always un-sanded, and the “Floor Grout” is always sanded. Now, this is unique to Australia. In the US and Europe grout is simply “sanded” or “un-sanded” and it is left up to the installer to decide where it is used, floor or wall.
It is important to note that un-sanded is made for joints 1/8 inch (3 mil) or less, and sanded grout is made for joints greater than 1/8 inch. The un-sanded grout is better suited to filling smaller gaps, flows better and has the ability to stay consistent. Sanded grout will not have the depth of penetration in the smaller joints, and the consistency will change as it is spread, some areas become heavy on the sand, and light on the cement component, this makes for very weak grout which will come out with regular scrubbing and pressure cleaning.
This is especially a problem on stone floors, travertine, marble, limestone, where a 1/8 inch or smaller joint is typically used. Due to the porosity of these stones, the sanded grout has an even greater problem staying hydrated and therefore has even less penetration.
 Aside from all the above, sanded grout makes grinding/refinishing very difficult, if not impossible. What happens is this: the grinding is done in a series of steps, starting aggressively with flattening, then onto the honing steps which bring up the shine. Now, when honing is being done the environment has to be very clean, any hard debris could get under the abrasives and cause scratches. So when the grinding is carefully brought up to a nice hone, and some very hard silica sand comes out of the unstable sanded grout joint this will leave scratches. This is why in most every case a stone floor with sanded grout cannot be fully flattened and restored. I have seen this in most floors I have looked at for restoration and it is very frustrating because it is so unnecessary.
Dimensional stone floors should always have joints of 1/8 inch or less, therefore ALWAYS should receive un-sanded grout. This is the international standard and it is time we got on board. It is simple common sense, and to see it done incorrectly is an embarrassment to the trade. Please spread the word.
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