Devin Devine, contractor based out of Blakeslee Pennsylvania, projects competed across the USA
contact devin@devineescapes.com
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Knapping: cutting flagstone with a rock hammer
aka rock pick aka brick hammer (watch the video, below)
Knapping/chipping is where you use a rock pick, or rock hammer to cut or chip off just a bit of stone at a time.
This type of flagstone cut is good for when you have a few inches, or less, of stone to trim off. Say you have a three inch piece of stone to cut–you just use the hammer to chip away, removing bit by bit, until you get there.
Tricks: the overhang and the ledge.
creating the overhang
The undercut is where you take your hammer and swing it down at an angle, looking to undermine the edge of the stone where you want to cut. Once you’ve created the overhang, now you have control for how you want to cut the top of the stone. What I mean is, now there’s a weak point along that whole edge. Now, you can trim from the top, with greater ease and get it just the shape that you’re looking for, without having to strike very hard.
The Ledge or bulge, is basically the opposite of the overhang. Often, a stone comes with a ledge already–a bulge on the edge of the stone that is ready to be hammered off in such a way as to create an overhang. Let me rephrase that….a flagstone that just has a straight edge, will be one that I need to hammer down on at a 45 degree angle, so as to create the overhang. However, if the stone is not straight edged, but has a bit of a bulge, or a ledge–then it will be easier to hit that bulge and turn it into an overhang. Or maybe the stone will come ready-made, with an overhang. In any event, once you have that overhang, then it will be easier for you to cut the stone right where you want to cut it, using the chisel end of your rock hammer. Here’s a video demonstration:
You can buy a rock pick aka brick hammer right here –and this is all I use, year after year. No need for carbide tips, for cutting 1 to 2 inch thick flagstone. In any event, you want wooden handled.
Another video, this one showcasing the hammer method, and two other ways of cutting flagstone:
For me, the hammer method, of chipping off small bits of stone at a time, is best for trimming most/nearly all of the small cuts, where I just have to remove an inch or two of stone. If there’s more than 5 or 6 inches of stone in to be removed, then I will likely reach for the saw or grinder–rather than wasting all that stone by pounding it into gravel (or wall hearting)–if there’s a large piece of stone to remove then I may use a power tool–that way the remnant may be recovered…..and put to good use in a wall. for example.
irregular flagstone walkway. For this project I fit the stones together fairly tight, yet still natural/unforced looking, but also allowed the walkway’s edge to be wild.
Related articles, DIY and hardscape how-to:
- how to split stone using feather and wedge
- what to use for under flagstones, concrete, sand, gravel, or what?
- what to put between your flagstones, sand, mortar, polymeric sand…..or stone dust?
- should you seal your stone patio?
- replacing the cement between flagstones, re-pointing
- how to clean your flagstone patio
- DIY hardscape consultation services–professional guidance on “how to build your own flagstone patio”
- how to build a dry stone wall
Again, tight fit, yet natural-looking. Many of these stones are fit using the knapping method described above but also many of the stones were cut using saws and grinders, with the sawn edge of the stone later roughed up, with the hammer.
Consultation services available:
Looking to build your own flagstone patio or natural stone hardscape? That’s great, but where to start……wouldn’t it all be so much easier and less intimidating–if you had a dedicated professional stone mason with over 23 years experience in the trade, and over 5 years teaching experience–and he was available to guide you through the entire process?
DIY Hardscape Help
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That was amazing! What you did with just your stone hammer and a chalk line! I’m going to give it a try. Slow and easy. Wish you were out here in CA!
I hope the technique works well for you! I may be in Sonoma County for a couple months, later on this year/next year, for some flagstone work.
I just watched the video and went right outside and tried it! It’s PERFECT! The guy at the building materials store told me not to try to cut the flagstone or break it, can’t wait to show him how wrong he was. It looks amazing! Thank you!
I’m glad the technique is working for you 🙂 I’ve definitely had suppliers, and contractors tell me it’s not possible to cut flagstone with just a hammer. For years, in my area, that’s what everyone said, “it just breaks like glass”. Show that building materials guy what’s up–and send him the video too, and/or give him an in person demo! He should give you a free hammer or something, in exchange for the education.
For splitting large stones, would you use a masonry chisel?
You mean a longer cut? If I have a 3′ x 4′ stone and it it’s going to need like a foot cut off of it (or any cut where I need more than a few inches of stone removed) then I’ll use a gas powered saw with a 14″ diamond blade–or, I’ll use a 4.5″ angle grinder like this https://amzn.to/3yCVop1
To cut flagstone using an angle grinder:
1. Always wear a respirator, always wear ear protection.
2. Mark the line to be cut with a piece of soap stone (can be found at depot/lowes with the welding tools, or online here https://amzn.to/3oLCOXp)
3. Use the grinder to score the line–cut it around an 1/8″ of an inch deep. This step is so you don’t lose the line that you drew with the soap stone. Once you start cutting the stone to full depth, the dust can potentially obscure your line
4. Cut as deep as the grinder will go (usually not all the way through a flagstone. A 7″ grinder will cut all the way through…but a 4.5″ angle grinder is dangerous enough. No need for a heavier 7 inch grinder, which is harder to use, more expensive, more expensive blades) Just cut as deep as the grinder will go and then snap with a brick chisel and a 3 lb mini sledge. What I usually do is actually perforate the stone with the grinder–I’ll cut the entire line about halfway through or less, then I’ll make a few stabs, or dives, cutting as deep as I can into the stone. Then, snap it using the chisel.
5. The diamond blade creates too perfect of a cut, so I then take the brick hammer and rough it up, chipping off just a small bit, 1/8″, maybe 1/4″ of stone from the sawed edge.
6. Alternatively, you can cut the underside of the stone instead. I mark the top of the stone where I want it cut, then tranfer that line to the underside, then cut as previously described–then flip it back over and hit it with the chisel, on the line. This will leave you with a natural looking break, that does not need to be roughed up with the hammer.
I love the look of your pictured irregular flagstone walkway. Did you use any edging material between the flagstone and the lawn, or did you just pack soil around the edges and reseed the grass?
I never use any edging material with dry laid flagstone. I just rake soil up to the flagstone and leave it to the home owner to re-seed.
Just make sure to not have any small stones on the edge bordering lawn…otherwise they may pop up, underfoot.
And thank you.
You mentioned somewhere you usually leave the flagstones raised about 1″ above surrounding lawn. I was wondering why this is your technique, instead of trying to keep them level to the existing lawn. Thanks!
Flagstone that is level with surrounding lawn may become a puddle, for one thing. The lawn may begin to overtake the edges of the flagstone too, with lawn actually growing over the stone.
Set the stone just a bit higher than surrounding soil, and rake the soil up to the flagstone, so that the soil ramps up to the top of the stone……this will shed water, keeping the stone surface a dry place to walk, even if it’s raining, and will make it so the lawn does not overtake the stone.