Hammerhead Stoneworks

I just added a new portfolio page for the Montford Terrace project, which is featured on the new postcard.

A couple of weekends ago, I led a workshop at the NC Arboretum on building stone benches. First thing in the morning we studied images of various benches, stone-cutting techniques and ways to move heavy objects safely and with relative ease. Safety was a recurring theme throughout the day. After the classroom presentation, we went outside and built a free-standing bench, a style I call castle-block for the big chunks of stone that make up the supports. The bench we built is now a permanent fixture at the Arboretum, a rest station along one of the trails.

To facilitate ease of movement, we cut the big stone down in the back of my truck. In this image, Ronnie is using a star bit chisel to notch shallow guide holes in the top of the stone. This gives the drill bit a place to sit, reducing the likelihood of the bit bouncing around and scarring the stone.

Everyone got a chance to use the drill and work at cutting stone. Here Judy leans into the drill to get the proper placement.

Since our cut edges were going to be exposed, we took some time to clean up the drill holes. Here Carol is using a handset chisel to knock off the cut edge of the bench stone. We put the cut edge to the back of the bench, less visible to passers-by.

We spent some time doing bench math, designing everything so that it would be the proper height and balanced as a structure and as an aesthetic object. Here Carol measures the thickness of the slab, the starting point for figuring out the math. I handed out the following worksheet to guide the design and layout process.

By cutting it in the back of truck, we made the stone more manageable, but it was still a heavy chunk. Jason uses a rock bar to move the stone from the pallet onto the ramps we have set up. Using 2″ by 12″ pressured treated lumber as ramps, we slid the stone down to waiting blocks and from there into place.

We used mortar to set the bench. This design can be done dry, but the mortar reduces the risk of movement, particularly since the bench is in a public place.

We all felt good as we finished up. The bench looked great and we had built it efficiently and safely. It felt good to be leaving something cool and useful for everyone to enjoy. Tre and Ronnie test drive the bench and pronounce it good.

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.

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.

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.

Register via the Arboretum’s on-line calendar.

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.

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.

These two benches were cut from the same slab of Tennessee sandstone. The first was built as a free-standing structure in a Chapel Hill neighborhood to celebrate the life of one of their most beloved members, Grandpa Tony. The bench is mortared and features an adjacent boulder with a small plaque. I call this type a castle block bench, named after the material used for the base stones. The second bench is in Asheville, adjacent to a sidewalk. The sitting stone, seatback and arm rests were all cut from same stone as Grandpa Tony’s bench. It is a drystone structure and built directly into the retaining wall.
Next spring I will be leading a hands-on class at the Arboretum on making a stone bench. We’ll be building a castle block bench together that day. The official class date hasn’t been announced, but let me know if you’d like to be updated when the class registry opens.

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.

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.

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.

Towards the end of fabricating 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.