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I have a boulder/rock that is about 2 feet long and 1.5 feet in diameter. It is too heavy to lift and I would like to break it into smaller pieces. Without power tools, are there any good methods besides going at it with a sledgehammer?

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    You might be surprised how little work it takes to break up that rock with a sledge. Repeated hits in the same spot will weaken the stone and it'll come apart before you know it.
    – isherwood
    Commented May 6, 2016 at 18:31
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    It's perfectly understandable if you can't lift it, but give a $20 to some neighborhood teenagers (or your nephews) and they'll be able to lift it. I did some googling and math and for that volume rock, even the densest rock on earth, basalt, would only be 844 lbs. Most rocks would be well under that and definitely within the capabilities of 3 men.
    – Zach Mierzejewski
    Commented May 6, 2016 at 20:58
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    Light a fire around it, feed it and let it burn for 3-4 days. Then dump cold water on it. Done.
    – Speedy Petey
    Commented May 6, 2016 at 20:59
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    I repeat, the fire option can be dangerous - if there is trapped water in the stone (more likely with some types than others) you can have a violent explosion with hot rock shards. While that will certainly make the rock smaller, it can have negative consequences to people and property.
    – Ecnerwal
    Commented May 6, 2016 at 23:24
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    Does it look cool? Craigslist: free rock.
    – Mazura
    Commented May 6, 2016 at 23:26

8 Answers 8

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You can go at it with a sledgehammer (or a smaller hand sledge) and a star drill, and then drive wedges into the holes (or if you are patient, fill the holes with water and let them freeze in the winter.) There are special wedges designed for use in round holes for splitting rock (feathers and wedges seems to find them). https://en.wikipedia.org/wiki/Plug_and_feather

Remember to use ear and eye protection.

Another approach from our practical forebears if you just need it out of the way would be to dig a hole 2-1/2 feet long, 2 feet wide and 3 feet deep next to it, then roll it in and bury it.

You could also build a bonfire on or around it, but that has some potential to become more exciting than planned for if the stone has trapped water in it.

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    The feather and wedge technique is the best way to split a stone by hand. There are plenty examples of it on youtube. You will need to use a hammer drill to drill a line of holes in the plane where you are going to split. Then insert the feathers and wedges. Tap each one in until tight. Work from side to side tapping each one lightly. Don't force it. Eventually, there will be enough pressure to split the stone. If you tried to break the stone using just a sledgehammer, you will only succeed in getting shards of stone to fly into your eyes.
    – Jason Hutchinson
    Commented May 6, 2016 at 20:23
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    without a sledgehammer was the question
    – Ben Welborn
    Commented May 6, 2016 at 20:42
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    No - "besides going at it with a sledgehammer?" was the question. Using a hammer and a star drill, and a hammer, feathers and wedges, is a VERY different process than beating on it with a hammer (alone.) Since folks seem to miss the concept, a star drill is a stone drill that is used with a hammer, no power tool required.
    – Ecnerwal
    Commented May 6, 2016 at 23:11
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There exist expanding compounds like this one: Ecobust, which are poured into predrilled holes and expand as they dry, splitting the stone (or concrete). It does require a power tool, unless there are already some cracks in your boulder, but a cordless hammer drill should be sufficient.

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  • without power tools (like a drill)
    – Ben Welborn
    Commented May 6, 2016 at 20:42
  • Still a good answer since the asker may have been thinking more along the lines of a jackhammer than a drill. In any case, this answer may be useful to others who have never heard of such a product.
    – Johnny
    Commented May 6, 2016 at 20:46
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    Star drill (chisel) and a heavy rock hammer could be used to create the holes.
    – Blackbeagle
    Commented May 7, 2016 at 2:20
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If it is a nice looking rock or has a particular shape, place it on Craig's list as a free item. I listed four 5" Blue Spruce trees I needed to remove to make way for a garage. Gone over the weekend and I didn't have to lift a hand.

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    So, bonsai? :-)
    – Wodin
    Commented May 7, 2016 at 5:29
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Without (electrical) power tools, or a sledgehammer:

Here are 10 options besides a hammer or Fire-setting... mentioned in almost every post (but more specifically, for best results use at least 300 lbs of wood or 100 lbs of wood and 20 lbs of bbq briquettes; let it burn overnight and then (in the morning) dump 15-20 gallons of ice-cold water on it.)

Option 1 Use a thermal lance to punch holes in it or cut it apart in about 30 minutes.

Option 2 Use an oxyacetlylene torch to cut or drill holes into it in 20 - 60 minutes.

Option 3 A large fresnel lens with a good focal point on a sunny day will melt a hole in it in anywhere from 20 minutes to 20 hours.

Option 4 After using any of the above methods to create a hole, insert black powder or TNT into the hole and detonate it (or use ecobust as mentioned by mustaccio).

Option 5 Use a gas powered concrete saw to cut this rock (maybe 10-30 minutes).

Option 6 Use a bull dozer, back hoe, or other kind of excavator to remove the rock (20 seconds).

Option 7 Use about 80 lbs of Thermite to turn the rock into lava (keep the fire extinguisher handy).

Option 8 Use a catapult or rocket to launch the rock into a larger rock.

Option 9 Shoot it with a cannon.

Option 10 Call in an air strike.

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    Option 10 seems like the best call. Planes aren't power tools at all. :)
    – user51961
    Commented May 7, 2016 at 0:04
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    That's silly, electric planes!
    – Ben Welborn
    Commented May 7, 2016 at 0:09
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    Is it? Planes don't run on just gas anymore. Lose your power now, you'll probably lose the plane. Especially if it's "all power." (Or so my aviation experience would lead me to believe.)
    – user51961
    Commented May 7, 2016 at 0:11
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    20 hours of continuous sunlight might be hard to arrange :)
    – Jasen
    Commented May 7, 2016 at 5:45
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    Nuke it from orbit, it's the only way to be sure
    – Corvus
    Commented May 7, 2016 at 14:54
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Use a crowbar and put another rock under it so that sections of it are unsupported. Now whack it with the sledgehammer a few times.

If you get lucky, it will have a crack in it and you can break it into pieces. Otherwise you can knock off sections from the end.

Worst case, use the plug and feathers approach described above.

Another technique is to make a large fire (e.g. bbq briquettes) on top of the rock, let it get super-hot, and then douse it with water, causing it to crack.

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    without a sledgehammer was the question
    – Ben Welborn
    Commented May 6, 2016 at 20:42
  • True... hence the suggestion to use heat cracking.
    – gbronner
    Commented May 6, 2016 at 20:45
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    The question is hoping for a better answer than the sledgehammer, he didn't categorically exclude it. When I fished a boulder (smaller than this, but too heavy for the garbageman to take) out of our front yard this is what I did--I managed to get a rock under it. The 6th blow on the unsupported part and it came apart.
    – Loren Pechtel
    Commented May 6, 2016 at 22:30
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Obtain a chisel with a rubber protector around the top, (more contact points and less chance of hitting yourself.) Proceed to hit this chisel with a rubber mallet or other leverage-providing, hard-ended object. By nature of the chisel's inclined plane, forward motion will cause the rock to crack and split along the business end's edges. Depending on the kind of rock, you will soon have a large enough area broken up to sufficiently hold the chisel without aid of your hand.

Now use your large implement, (potentially a sledge) to apply a significantly greater force than used before, (making sure to use protective equipment, and both hands,) and you will have a wonderfully large split, or at least a significant compromise of the rock's structural integrity. Repeat this process as many times as needed. Through this, with little expense, like using a wedge with an ax to split firewood, you can break the rock into small chunks, which can subsequently be taken away.

You will notice the appeal in using an incline plane to do the work for you, preventing injury and potentially larger amounts of expense.

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You have no sledge hammer, no power tools, and it's too heavy to pick up? That leaves you with zero options that do not require or produce an explosion. Besides someone taking it of your hands, which is unlikely, seems to me, the simplest solution to dig a sufficient hole and just bury it.

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If it's in a place that safe to do so, build a fire around it. Let it get very hot. Dump ice water on it. It will shatter.

Source: My dad was a farmer and he told me this a long time ago.

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