I am using 2-4 foot limestone boulders as rip rap in a nearby canal. I'm trying to avoid buying EXPENSIVE mining/lapidary equipment. It is very SLOW work however to cut off the sides of the boulders to prevent them from rolling down the embankment. I have been using 9 inch grinders with diamond blades. Turns out limestone is kinda hard. It is so porous, I thought it would be faster cutting. I have used feather and wedge, but with mixed results on this very holey limestone. Are there any better ways?

  • Can see this using just hand tools. youtube.com/watch?v=otiO_wKCwEc
    – crip659
    Dec 22, 2021 at 20:58
  • 1
    Drill and split with the grain - multiple small chisels hammered in.
    – Solar Mike
    Dec 22, 2021 at 21:09
  • 10
    @SeanAtkinson -- is this a situation that your local stormwater/water-resources authority is like, refusing to fix? Dec 23, 2021 at 1:38
  • 7
    I think it's worth stating that undertaking clandestine public works projects without permission on city or other property you do not own is opening the door to a potential legal nightmare.
    – J...
    Dec 23, 2021 at 9:11
  • 1
    @SeanAtkinson I suspect the Insane Clown Posse would actually not appreciate the comparison Dec 24, 2021 at 16:03

4 Answers 4


Drill and split with feathers and wedges. I can't imagine using a grinder to do this work.

SDS max rotary hammer and 4 cutting edge carbide bits.

  • J.. I gotta protect my property, it’s not like they are. Also , clandestine? “ kept secret or done secretively, especially because illicit” Sounds a bit much. Simply protecting an embankment. Neither in secret not illicitly. Dec 24, 2021 at 5:21

Option 1

Use concrete to stop the rocks from rolling, you can get white cement (for a small extra cost over the price of grey cement) and if you use it with white aggregate (e.g. quartz or marble chips) it will be basically the same colour as limestone,.

Option 2

Get a larger drill or electric jackhammer. if you don't like the price hire one for a few hours and see if it does the trick.

Option 3

A grinder is the wrong tool, you really need a wet saw to cut rock, the water will reduce the amount of airborne dust, and save quite a lot of wear on the expensive blade.

If you take some rock samples to the tool hire place they may be able to offer advice and may even let you try their tools out for free.


Find a source for smaller rock that will not have a tendency to roll. In a very similar situation I used defective bricks. There was a brick factory in the area and I found they sold defective brick very cheap, essentially fill. The full and half bricks were very stable in a very fast river bank, faster than your flow. In a heavy rain my stream rose over 12 feet, sort of a ravine with flat shorelines. So a half brick size gives a general idea what size you need. My soil was sand so very susceptible to erosion. I did add many cuttings of water tolerant brush like redtwig dogwood, but the brick was essential .

  • 2
    blacksmith37- Thank you for your insight. The thing is, I can't use anything but 100% "native" plants or fill, so no one gets the idea we are trying to just get rid off garbage., plus neighbors would complain if I use anything but. Yes, I am def using plants as well. Other sources of rock, meaning selected rock, gets a lot more expensive. Dec 22, 2021 at 22:30
  • 1
    I did not necessarily mean brick , but something like a large size crushed limestone. Redtwig dogwood is generic in US and Canada except the southern states and was the best of several plants I tried. Dec 23, 2021 at 15:38
  • Gotcha, but currents displace smaller boulders. Also keeping to the same size that the city used in one area they did manage to reinforce. Dec 24, 2021 at 5:21

Do you get cold winters?

A traditional mining technique in the UK was to expose the limestone bed, cut vertical holes and grooves in selected places (with hand tools!), fill them with water, and wait for a winter or two to do the rest. The water froze, expanded, and cracked the rock. With a quarryman's skill, it cracked into rough cuboids that could be built into walls without further shaping being necessary.

Anyway, experimentally, you could try drilling a few vertical holes into some boulders, filling them with water, and wait to see what winter does to them. Experiment with hole diameter and depth and spacing.

Obviously if you do not get cold winters, this idea won't fly.

The other answer which probably isn't what you want, is to use gabions. These are enclosures made of tough approximately 2 inch square mesh) , something like two feet cubed. You fill them with crushed rock. By the time the wire mesh rusts, weathering, dust, and vegetation has bound the crushed rock together. It's a common technique (in the UK at least) for reinforcing unstable river banks or embankments.

  • 3
    map above indicates the OP is at the southern end of Florida, so freeze/thaw cycles aren't going to be available. Dec 23, 2021 at 12:24
  • Expanding mortar (eg expando) could do the job instead, but probably no better than the already rejected "feather and wedge"
    – Jasen
    Dec 23, 2021 at 13:49
  • One cut per year or two seems like an impossibly slow way to go about this... feathers and plugs have been around for thousands of years for a reason.
    – J...
    Dec 23, 2021 at 17:18
  • @J... It was a method used for mining Cotswold stone and similar before power machinery or diamond saws. Very economical of human effort (but needed skill to get the cracks in the desired places). You prepared as much stone as you needed, then just waited until spring. (The UK is now too mild to use this method - many years, no snow, no really hard frosts).
    – nigel222
    Dec 23, 2021 at 17:35
  • @nigel222 Sure, the economy/lazy factor is obvious - as long as you're not in a hurry for your blocks, I suppose, yeah, no doubt it would work.
    – J...
    Dec 23, 2021 at 18:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.