Cobblestone Patio

The defining feature of my current project is a circular cobblestone patio in Asheville’s historic Montford neighborhood made of materials gathered by the homeowner over the last 30 years.

circular cobblestone patio

The homeowner spent fifteen years salvaging old cobblestones from around Asheville so we could make this circular patio space,

Colorful Cobblestones

The cobblestones are very diverse; I’ve found at least three distinct types of granite. They have all weathered differently and some are quite smooth from years of use as roads. Since there was a limited supply, I split most of them in half lengthwise. This effectively doubled my stone supply and added colors to the palette. While the top might be a granite grey, or green with algae, the bottom may be brown or orange, depending on the type of soil it has been sitting in for the last few decades. Once split, the inside of the stone also became a usable surface, always much brighter and sparkly than the weathered outside. A couple of the stones actually have old paint on them, from their days as roadways. As a result the cobblestone patio is quite colorful.

Cutting Cobblestones

I have tried every different way I know to cut stone and have found the most efficient and neatest way to split the cobbles is using a type of chisel called a hand tracer. I scribe a line all the way around and around the cobble until it splits in two. The grain of granite is ideal for this type of technique; it’s very hard, dense stone, but it responds predictably to the chisel’s persuasion. The local metamorphic stones are less cooperative. I start out lightly, making sure the line is fairly straight and well established before I really lay into the stone. Once I get going, I can hear the stone starting to split, and I ease up, paying more attention to the places where it still sounds solid. A sharp chisel is a huge asset and I have been bringing the hand tracer home every night for a run over the bench grinder.

Cutting A Stone Circle

I used the hand tracer to remove large chunks of the center stone, a circle cut from a another salvaged piece of granite. I didn’t have a compass large enough to draw a circle on the stone, so I made one with roofing felt, a nail and some soapstone. I traced the circle on a piece of roofing felt and then laid that template over the stone.

Once I had the basic shape of the circle cut, I switched to my smaller, sharper chisels, which give me more control, to hone a more accurate shape. Though the patio needs one more ring to be completed, I dropped the circle stone in the center on Friday afternoon, to check the fit. The whole cobblestone patio makes me think of a flower.

 

Column Theory: Stone Mailbox Vault

Stone Mailbox Vault

Last week I spent a good bit of time creating this structure within the column to house the biggest mailbox I think I’ve ever seen. I cut these quoins from step slabs, using petty much every technique I know how to tim them down. The cut-off saw was too loud and dusty and the line would wander over the full 36″ of the stone. Using the hand tracer chisel worked, but was really only efficient when I was cutting the shortest lines. Eventually I settled on cutting a clean line at each edge with the small grinder and then using feathers and wedges to cut the rest. This allowed me to keep my quoins fairly symmetric, but let me go more quickly than I would with chisels alone or even using the saw. Perhaps someday I will do a time trial to see which is faster, though I suspect the old school wedges (and an electric hammer drill of course) are faster than my Stihl saw with a diamond blade on it. Feathers are more fun too.

Stone Mailbox Vault

This is a detail of the armature that I am building the columns around. This is intended to provide a place for the wooden cross pieces to be hung and held away from the stone work. By doing this, the wood is more easily maintained and switched out as needed. It also protects the stonework, by reducing the chance that the wood will soak up a bunch of water and hold it against the mortar. Whenever wood juts into stone work, it inevitably creates a weak spot in the stone structure. This armature design also provides a place where I can mount my corners template, a piece of plywood with string stretched plumb to the footer. I got this idea from Fred Lashley; I don’t know if she invented it or adapted it from some other source.


A banker is a mason’s work table. You can’t see from this angle, but this table is minutes away from falling over; it has a significant, persistent lean. That’s a chunk of Arkansas Hackett sitting on the corner.

Cutting Lintels

Cutting Lintels

Here is the step-by-step process I followed for cutting lintels for the pig roaster.

Here’s the stone I’ve selected and an assortment of the tools needed. The blue lines on the stone represent the cuts I’ll be making, one way or another. I decide to cut the right end off first, using feathers and wedges.


Before I use the hammer drill, I make small starter holes with the star-bit chisel. This prevents the drill bit from chattering on the stone, missing the mark and leaving unsightly scars. Before hammer drills, star bits were a traditional way to cut stone- swing the hammer, spin the chisel, swing the hammer, spin the chisel and on and on.


When cutting granite, I usually put feathers and wedges on three sides. To help guide the cut through the edges of the stone, I use my hand tracer, a recent purchase from Trow and Holden, to score a line where I want the cut to go.
Cutting Lintels

Sweet!
An argument could be made for making this cut with the hand tracer alone; granite is hard and heavy, but it behaves very well under tools. I decided to use the feathers to save time. You should trace all four sides and that’s no small feat with a stone this large, at least working by yourself.

Cutting Lintels
I followed the same process to make the longer cut along the width of the stone. Note how much straighter the ends are, where I traced the edges before splitting. It might have been a good idea to trace the whole line, though the rough line is in keeping with the overall aesthetic. I placed one wedge at the bottom of each side to guide the line.


The pencil line indicates the last cut to be made, to trim the top of the lintel. This is the face of the stone, freshly split showing a lovely line of quartz that will center over the opening of the roaster. Because of the clean line I want and the proximity to the edge of the stone I elect to use the hand tracer rather than the drill and wedges.

Cutting Lintels
Here’s the risk of this operation- I am cutting very close to the edge of the stone, particularly as it tapers towards the bottom. It is very likely that the cut I’m making will choose the path of least resistance out of the stone, which would be to the back, rather than the bottom. The top of the stone will spall, leaving me with stone to remove by other means.


The hand tracer is surprisingly effective; it cuts a very, very clean line.

Unfortunately the top of stone spalls, leaving excess material on the top where my cut was trying to remove the thinnest flake of stone. The blue line indicates what remains to be removed. The grinder is my weapon of choice.


I score the top of the stone with my seven inch grinder using a diamond blade. I put the score lines about an inch apart. I then use my chisels to remove the excess material. Notice the dimple on the face closest to the camera; a matching dimple on the opposite side made it possible to lift the stone.

Cutting Lintels
All that’s left is cleaning up the drill holes a bit.

Cutting Lintels

Complete!