Spring 2010 Classes at the Arboretum

The new class schedule for the North Carolina Arboretum was recently announced. I am leading three stonework classes this spring. DIY Flagstone Paths & Patios will be offered twice, on Saturday April 10th and on Friday April 16th. In the morning session, we discuss the basics of drystone flagging: necessary site prep, the principles of good structure and varying joinery styles. In the afternoon we go outside to the stone classroom and practice the essential skills: moving stone safely, shaping individual pieces and leveling the patio.

I am offering a brand new class this spring, called Stonework Special Projects: Making a Bench on Saturday May 15th. In the morning we will discuss the design and structural issues of building a stone bench. In the afternoon we will build a freestanding bench ourselves. Topics of note including cutting stone with feathers and wedges and how to move large stones safely.

 

Radial Steps: Getting started


On Wednesday I built the riser for the first step, seen here. It was a warm enough day, but only ten percent of my stone was visible; the rest still covered by snow. These steps are structural, meaning they’re stone all the way through; there’s no block or concrete, except for the slab underneath it all. They will extend almost all the way to the cut bank. These steps and attached columns are mortared. The adjacent retaining walls will be drystone.

Tread for bottom step

I spent Thursday in the shop, seen below, fabricating these tread stones for the bottom step. As with the Eight Leaves project I made paper, then roofing felt templates. The paper templates for this step are taped to the wall behind the saw. The roofing felt templates are piled on the table. This time I used my seven inch grinder instead of the five inch. These radii are more gentle on these steps and the bigger blade made it easier to get through cleanly. The downside is that the bigger grinder kicks like a mule when the blade catches.

Bluestone Fabrication: Making the 9-Story Patio

Bluestone Fabrication

The first designs were pencil lines on paper, as I tried to create shapes and fill the space in a balanced way. The pencil sketches were on an approximate scale. Once I had a design I liked and the clients had approved, I created the drawing above in Adobe Illustrator. I made it full scale, which means the document itself, if I could print it on a single sheet, would be exactly the size of the patio, five feet deep and almost twenty feet long. The biggest challenge was keeping the arced lines smooth. I freehanded each line, but found several shortcuts to eliminating the bumps and bounces of my hand drawn lines. I use a Wacom drawing tablet, which helps a whole lot.

You might notice that the numbering scheme is also a lettering scheme- I substantially changed the design halfway through and couldn’t start my sequencing all over again.

Since I don’t have access to a large enough printer, I had to cut the document into pieces. I outputted a couple dozen PDF files that had a shape or two on them. I twisted and turned the original document to reduce how many prints I needed. It was still a huge roll of prints. I had them done at Henco Reprographics, far and away the best printers in town. I cut each shape out, a few at a time because it proved to be so tedious. As it turned out, making the templates was just as time consuming and considerably less fun than making the stones. Though it was less dusty.

I transferred the paper shapes onto fifteen pound roofing felt. It’s considerably more durable than paper and waterproof. I fastened the paper to the felt with masking tape, to make sure my shapes didn’t morph during the cutting. Using felt for the templates was an idea I borrowed from fellow Stone Foundation member Karl Opanowicz. It worked perfectly and withstood all the abuse I could mete out.

Most of the stones had at least one straight side, which is where I started my cuts. I had to place the templates quite precisely as they barely fit on the stones. As it was, I purchased over three tons of material to find these 27 stones. There are only a couple of stones left over big enough to be cut for this design, most of which were rejected for being boring. This stone, the thickest of all of them, is sitting on the table of my Achilli bridge saw.


The Achilli bridge saw is a job site granite fabrication tool. It can support a 14 inch diamond blade and has a recirculating pump in the table reservoir that sprays water onto the blade, keeping it cool and knocking down the dust. The bluestone was so soft that I could plunge cut it, meaning I didn’t have to make multiple passes. It zipped right through.

Bluestone Fabrication
After the straight lines were cut I moved onto the arcs. I traced these lines with a piece of soapstone. It’s more durable than pencil lines, but can be washed off as desired. The wax crayons carpenters use leave permanent markings on stone. From this picture you can see how close I am to the edge of the slab.


I used a five inch Makita variable speed grinder for the curved cuts. In this image it’s outfitted with a 4 1/2 inch blade and the grip is on the wrong side; this was an early stone in my learning curve. Matt of Rockstar Marble and Granite set me on the right course by switching me to a five inch blade and swapping the grip around. I faced the blade away from me and dragged it from left to right, sending the spray of dust away from me. By holding the grinder straight up and down I was able to get very clean and deep cuts, though I had to flip several stones to finish the job. What a delightful mess.

Bluestone Fabrication

I used a cup wheel to grind off any excess along the edges of stones. While the sides aren’t visible, the tolerances between the stones are so tight, there’s no room for any extra material. During installation on site, I also used a zero tolerance wheel, another granite fabrication tool, to fix shapes and tighten the joints. These are both fairly aggressive tools and I was able to rip my way through the excess without too much trouble.

Bluestone Fabrication

Rough draft at the shop

Towards the end of the bluestone fabrication I laid it all out at my workshop. I didn’t fuss too much with the joints while I was fabricating it, figuring that there would be a lot to do on site to get it exactly right. It would have been hard to get them exactly right at the shop because the stones were varying thicknesses placed on a level surface. A slight discrepancy in level can change the way two stones interact. Most of the stones needed at least some attention to snug in the way that I wanted. The stone fabricated above- number 9- is visible at the bottom left of this image. On the patio, it partly spans the doorway, one of the reasons I chose such a thick slab.

Bluestone Fabrication

Ready to go

Details: Eight Leaves on Nine Stories

Details: Eight Leaves Nine Stories

Details: Eight Leaves on Nine Stories

The eight leaves are of blue bluestone; six are visible in the image above. The background is made up of what’s known as off-color bluestone. It runs green to brown, but I chose only the browner tones for this piece. Texture was important too. Several pieces have reeds or stalks of plants embedded in the stone’s surface.
The patio is laid dry, but the joints aren’t filled with sand or gravel, as is usually the case. This keeps the joints dark, a detail which I absolutely love.

Details: Eight Leaves Nine Stories
The nine stories is how high up this small patio is over Asheville. It’s situated on a ninth story balcony in a downtown high-rise. Thankfully there was an elevator. My big truck barely fit in the parking garage.
In these images the stone is fresh wet, having just been washed down. I’ll take further images when the stones aren’t so sopping. Stone looks best damp, not wet.

Details: Eight Leaves Nine Stories

The design was inspired by a rug fragment, seen in the top left corner of this image. I made a color study based on the sample and created a design that borrowed from the rug. The balcony railing has similar swooping lines and even some of the furniture features a subtle leaf design. The rug itself, when completed, will be placed inside the condo, opposite the balcony, designs reflecting each other through the floor-to-ceiling wall of windows.
Crafting the stones was a fascinating process which will be detailed in a forthcoming blog entry. I had full-sized templates printed from my design, shown below.

Details: Eight Leaves Nine Stories

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!

Cutting an S shaped Line in Stone

Cutting an S shaped Line in Stone

Up to this point, every time I’ve cut a stone using feathers and wedges, I have done so in a straight line. I decided to try cutting a S shape out of this particular slab of sandstone paving because it was just too large for the walkway under construction; it would unbalance the whole composition. I wanted a sinuous line to accent the rolling shape of the path and to avoid creating a uniform, tiled feeling with long straight lines and square stones.

Cutting an S shaped Line in Stone
I drew the line over a few times, trying to get the right shape. I wanted a subtle curve, figuring it would be easier to accomplish. The X’s indicate where the drill holes be, evenly spaced. This is the back of the stone, so my scribbles and drill marks will be unseen.

Cutting an S shaped Line in Stone
I drilled six holes. Why six? Because that’s how many complete sets of feathers and wedges I had at the time. More would have been better. The holes are fairly shallow, about two inches. The stone itself is only three inches thick. I was careful to not punch the drill bit through the stone, as it would have created ugly knockouts.

Cutting an S shaped Line in Stone

I placed the wedges so that they turned along the line. This ensures that the force applied pushed the stone apart along the desired line. They look like soldiers marching.

Cutting an S shaped Line in Stone

Ah, so close. The actual split wandered from the desired line at the very bottom of the stone. Looking at it now, it’s clear that the split followed the path of least resistance. Another wedge even closer to the edge might have helped this, as would have reorienting the line so that the desired line followed the path of least resistance. Tracing the desired line with a chisel might also have been helpful.
There’s a lot of surface flaking where the feathers are set. I believe the wedges are a fraction to big for the drill holes so that they bind at the top and cause the stone to pop like this. This was a secondhand set of wedges that I have since replaced. Another reason to do this on the bottom of the stone.

Cutting an S shaped Line in Stone
Here are the cut stones in the pathway. The two big, rust-colored stones to the left side of the image are the cut stones flipped and set. Note the ‘dog paw’ pebbling just above the gray stone, to honor Dixie, a regular visitor to my lunches during the project.

Setting the lintel


Today I set the lintel on the fireplace at the cabin in Mars Hill. The lintel is 46″ long and approximately 9″ by 9″ square. I cut it from a large slab, that weighed just shy of 1900 pounds. Here I am waiting for a fissure to emerge. I’m cutting the end of the lintel off using feathers and wedges. It’s very gratifying to listen to the stone as it splits; it sounds like ice.


Reid and Zach were on hand to help with all the lifting. We used 6″ by 6″ blocks to make a very sturdy tower in front of the fireplace. This made it much easier to lift the stone into and out of place, three times total. The first time I saw the general placement and marked the bottom of the stone for shaping. The second lift was to check the fit. I made some minor shaping adjustments and then the third lift was onto a mortar bed.


The lintel leftovers, all 1,000 pounds of it, made a good step onto the cabin porch. We will adjust grade so that the step down is consistent across the face of the step, which will effectively hide the oddball build up stones.

A couple of the drill holes on the face of the steps broke such that they can hold marbles. These are easily removed by kids, but the others are a couple of inches down a hole that didn’t break open at all. Those will be tougher to get.

Below is a detail of the break between the lintel and the step stone, just after I split them.