Bench Class

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.

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.

 

Bluestone walkway

Bluestone walkway detail

I built this walkway last fall using Pennsylvania bluestone. In this image you can see both the true and full-color bluestone. The path is 42″ across and laid dry. There’s a small set of steps in the middle; the very straight line at the bottom of the image is the back edge of the top step. The steps are Tennessee sandstone, but they fit the color palette well. The path is drystone, with no mortar or concrete at all. It leads to the main entrance of a private residence.

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.

Truth window


Yesterday I got the fireplace up to mantle height. Once I have some design discussions with the woodworker about the installation of the mantle, I’ll finish out the area above and focus exclusively on the chimney. As it is right now, I have a long walk to retrieve forgotten tools.
Limited lighting in the cabin, hence the lower quality of the image.


This a view of the wedge and shims that got stuck in the end of the lintel. I’m calling this the truth window, after the openings they leave in a straw bale wall to show what’s behind the stucco rendering.


This little stone sets into place nicely, but is easily removed to see what’s behind the truth window.


The biggest spider I’ve ever seen not in a pet store. He was about two inches across, which doesn’t sound that large, but he certainly caught my attention. This is a wolf spider, a roaming hunting spider. A good reminder why I should wear gloves in the stone pile. All indications suggest this will be another banner year for black widows.

Assorted pics


I lost a wedge and set of feathers in the lintel stone. The stone broke cleanly, but this wedge, at the front edge of the stone, didn’t split quite right. The wedge remains, well stuck in the stone. In this picture, the wedge is set about two inches back from the front of the fireplace. I am leaving a ‘truth window’ in the stonework, so that you can look inside this little pocket and see the stranded tool.


This is my work space in the cabin, morning light filtering in. The recessed floor is where the hearthstones will be set.


There are marbles throughout this project, including this playful little dragon, well hidden in the face of the fireplace.


This tiger beetle has been a shiny emerald skittering around my stone piles.


This spring has been the wettest in years and the salamanders are in seventh salamander heaven. Everyday I see a few, under stones, in the creek or sometimes just walking around in the damp leaf litter. I believe this to be a Mountain Dusky Salamander, but I am not certain of my ID.

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.