We here this all to often, from homeowners and installers alike. “We asked the tile shop what grout to use with natural stone and they recommend sanded grout.” There seems to be endless confusion or just a general lack of concern about grout. Until there is a problem.
The simple solution is just to always use un-sanded grout with limestone, marble, travertine and other softer stones.
Notice this brand new limestone floor in Pittsburgh. One of the most known tile shops in Pittsburgh recommended the use of sanded grout. It is a easy mistake, after all, wide grout joints, like these require sanded grout. So if the homeowner failed to mention it was natural stone it would hardly be the fault of the tile store. But regardless of why it was recommended, it certainly messed up the finish of limestone, leaving a scratched dirty looking floor. The fix is costly but at least it can be fixed. We have seen sanded grout ruin brand new porcelain and with porcelain there is no fix.
How would I have installed the floor above?
I would have used a smaller grout lines with un-sanded grout. What If the homeowner really wanted the wider grout joint?
I would have clearly communicated with the customer my concern about the choice of using a wide grout line. That we would have to use sanded grout and it will result in a scratched surface. Then I would have them sign a waiver holding me harmless from any damage to the stone.
Some people just love the look of the wider grout line. So what else could a installer do to help prevent damage. Use a mix of half and half sanded and un-sanded grout. Still have a waiver signed, not only for the stone but also for the grout work, it’s not going to be as strong. But this method usually prevents scratches and will last a long time!
Reasons why installers in Pittsburgh keep making these mistakes:
1: A general lack of training installing natural stone
2: They were giving bad advice or training
3: Frustrations with un-sanded grout cracking
4: Homeowners refusing to listen to properly trained installers.
5: Poorly labeled product. Many of newer epoxy and urethane grouts say on the box the are safe for natural stone but are proving in the field that they are not. A general rule to follow is if the grout feels rough it’s to rough. If you are using a newer type of grout on the market just mix some and judge by feel. Is it rough or nice and smooth? A smooth grout isn’t going to scratch. But these rougher epoxy, urethane, and grouts with fiber glass additives will scratches every time. This is not to say never use epoxy grout, just make sure it’s not going to scratch the floor. Don’t trust what you have read or heard but judge with common sense! If it’s rough it’s going to scratch