The river rock floor that was installed in my shower has some areas that can be uncomfortable on the feet where the rocks are somewhat pointy. Any ideas on if it's possible to grind these pointy areas down? I was thinking of using a diamond grinding cup on an angle grinder. But I'm also thinking this could go horribly wrong if it yanks rocks out of the floor and sends them crashing into the tile. Any hope for this?enter image description here

2 Answers 2


By coincidence, I saw a video just the other day of an artist who takes river rocks and grinds decorations into them with a Dremel tool and a diamond bit. So yes, they can be ground down.

An angle grinder with a diamond grinding cup would do it, but like you said, it may dislodge stones. A safer (but slower) approach is to use a Dremel tool with a diamond bit (like a drum or disk). Feel around the surface for pointy areas and just smooth those spots. The stones look polished (unless that's just a shiny sealant). You can repolish the ground surfaces by using successively finer polishing disks (sets are sold for touching up granite counter tops; you can find them at large hardware stores or places like Amazon).

BTW, the grinding will produce a lot of stone dust. Seal the drain so you don't clog it up. Wear goggles and a dust mask. The dust will be extremely fine, so clean it up with either damp rags or a vacuum with very fine filtration, like a HEPA vac. A vacuum with a regular collection bag is likely to blow the dust out the exhaust.

  • Not just any old dust mask, either. Use a properly fitting half face with a P100 filter. Mask off as much of the rest of your house as possible with dust barriers. I'd protect the walls with plywood and skip the dremel because I (personally) wouldn't want to prolong a slightly miserable job. Commented Mar 25, 2018 at 15:38
  • @AloysiusDefenestrate, the dust was another reason for recommending a Dremel tool. I've done several stone and concrete cutting or grinding jobs with an angle grinder and diamond cup or disk. You're right, it generates tons of dust; clouds that get everywhere. I'm still cleaning up my basement a year later from dust generated in a couple of minutes in one corner. We covered everything in plastic and the dust still got into every nook and cranny of the entire basement. I completely sealed a room with plastic before cutting a marble table. (cont'd)
    – fixer1234
    Commented Mar 25, 2018 at 17:33
  • Every surface in the room was caked in dust and some dust found a way out. The stuff is extremely fine and stays airborne for a very long time. A Dremel tool generates far less dust, and it doesn't travel nearly as far. The grinding time will be longer, but there's much less prep and cleanup time (the miserable part of the job for me).
    – fixer1234
    Commented Mar 25, 2018 at 17:34
  • Good ideas all around! I found several options for 5" polishing discs but all are limited to 4500RPM and my angle grinder is not variable speed and operates around 11K. I'll look into renting something. I'm definitely going to completely seal the shower area to keep the dust down and also probably wet polish to help. Why do I have to seal the drain? I was planning on washing all the dust down the drain.
    – Andrew
    Commented Mar 26, 2018 at 12:17
  • The dust is extremely fine sand. The individual dry particles will float around in the air. But when wet, it clumps together in a very dense mass. It can also absorb soap and other things that go down the drain, and mineral concentrations from the water, that can act like a binder, turning it into something that resembles concrete. It will collect at bends or traps in the pipe, creating a plug. It will snare and build up hair and become an ongoing maintenance problem. So it isn't stuff you want to dispose of in your drains.
    – fixer1234
    Commented Mar 26, 2018 at 18:55

Yes, many commercial floors are made that way and a couple homes in my neighborhood. My guess is that is not a job for homeowner equipment; maybe rental equipment.

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