For this build, I pulled in several elements from different areas of life and combined them into one cohesive design. A bench that has an organic stone as one leg and elegantly transitions to refined joinery and bent lamination, emulating a bridge.
The stone is a granite boulder; the top and legs are African Mahogany; the Arch, cross braces, and wedges are Walnut. The whole thing is finished with a satin wipe-on poly. This piece became part of my Boulder Furniture Arts Collection.
Inspiration came from:
Eric Reinholdt 30×40 Design and his Pond House design
Go here for more info on the custom bench project
SPECIALTY ITEMS USED IN THIS BUILD (affiliate links)
• West Systems Epoxy
• Starbond CA Glue https://amzn.to/2BvNG3r
• CA Glue Accelerator https://amzn.to/2R7Ortc
• Resin Glue https://amzn.to/2R3VKSR
• Pro For Sho Hearing Protection https://amzn.to/2wkQJbR 10% OFF Coupon Code: BENHAM84
• Lincoln Mig welder 180 pro https://amzn.to/2w851NT
• Minwax wipe on poly https://amzn.to/2AWjMWO
Building a Bench Around a Boulder: My Most Ambitious Project Yet
So today I’m tackling what might be my craziest project to date – building a bench that incorporates an actual granite boulder as one of the legs. Yeah, you read that right. A rock. As furniture.
The Stone Leg Challenge
Let me start with the most physically demanding part of this whole build: dealing with the stone itself.
This granite boulder was way too heavy for me to lift on my own, so I had to break out the engine puller just to get it out of the back of my truck. Once I managed that, I rolled it around to the back of my shop and grabbed my angle grinder to score around the bottom where I wanted to cut it.
I cut as deep as the grinding disc would allow, then switched to cold chisels to break the bottom section off. My goal here was to make it light enough that a client could actually pick it up and move it by themselves – you know, practical furniture and all that.
But here’s where things got really intense. I started grinding out the inside of the rock with a 4″ angle grinder. I’m not going to sugarcoat it – this was absolutely brutal. It took me an entire day to completely hollow out the inside of that rock, and let me tell you, my arms grew three sizes that day. I felt like I’d done a year’s worth of workouts in eight hours.
Why Would Anyone Do This?
As I was posting progress pictures on Instagram, I got the usual friendly ribbing from people asking what on earth possessed me to come up with such a crazy design.
The jumping-off point actually came from an architect friend of mine, Eric Reinholdt from 30 by 40 Design Workshop. He designed a house where they took a granite boulder from the building site, craned it through the roof, and turned it into a fireplace in the living room. How cool is that?
There were a lot of challenges in fitting such an organic piece into a contemporary setting, and it really got me thinking about how I could incorporate stone into my own work.
The idea bounced around in my head for quite a while as I tried to figure out what the piece should actually look like. Then, on a trip back to Oregon and a short hike through the Cascades, it all came together – bridging the gap between refined joinery and organic shapes.
Carving the Top
Once I’d ground out enough of the rock so the weight was manageable, I started milling the lumber for the bench top.
After the glue dried, I began the process of carving out the opening for the rock to pass through. I started by drilling some holes through the top, then chopping out the opening with a chisel.
To figure out how much wood I needed to remove, I set the board in place and traced the shape out on the underside.
Now, for those of you who were yelling at your screen that I was going to ruin my angle grinder on the stone – you’d be absolutely correct. With a power carving disc installed on the grinder, I started relieving the material up to the line I’d traced earlier.
I test-fitted as I went, using a mallet to tap on the top so the stone would dent the wood and leave a mark showing me where to grind next. As I got closer to the stone fitting properly, I switched to some smaller burrs and just kept repeating the process until I got really close to a nice fit. This took most of the afternoon.
Once I was down to the final fitting, I switched to hand rasps and files, slowly removing material until I was happy with the fit. The final step was using sandpaper to round over any sharp edges and create a little breathing room between the rock and wood. This space will allow for some wood movement during seasonal changes.
Building the Leg
Now that the carving was taken care of, I moved on to gluing up the leg.
Once the glue was dry, I set up a stacked dado head in the table saw to cut the tenon. The tenon was going to be wedged in place, so I used my shop-made jig to safely cut two slots in it to accept the wedges.
To add some visual interest to the leg, I used the band saw to cut a few tapers, then cleaned up the saw marks on the jointer.
Then I milled some walnut for the wedges. To create the wedge shape on such a thin strip, I cut a notch in some scrap wood to help hold the piece while I used a hand plane to create a taper on one end – just enough so it would slide into the slot on the tenon and tighten up nicely.
I made a jig that fit around the tenon and used it to route out a mortise in the top of the bench. I squared it up with a chisel and did a quick test fit.
Connecting Wood to Stone
To add some additional stability to the bench, I made a custom bracket to bolt the wood and stone together. This required drilling a few holes where the wood and stone met. I used a glass drill bit cooled with water to drill out the holes in the granite.
Of course, with the shape of the rock being all over the place, it was hard to get a reference for what would be level to the benchtop, so the steel rod ended up pointing downward.
To solve that problem, I cut a notch with an angle grinder, bent the steel, did a little test fit, and filled the void with a fat weld.
I cut a piece of flat bar to weld to the rods stuck in the stone, drilled some holes for the bolts, and welded it in place. Then I transferred the bolt hole locations to the benchtop and drilled and tapped the holes for the bolts.
Creating the Arch
Now, moving on to the arch support.
I made a quick bending form out of plywood and covered it with packing tape so the glue wouldn’t stick to it. I cut some strips from walnut to bend around the form to create the arch, and glued them up. When I glued them together, I made sure to keep them in the same order as I cut them so the grain would blend together, hiding the cut lines.
After the glue set up overnight, I cleaned up the squeeze-out at the jointer and cut it to length with a Japanese pull saw.
I scribed the angle of the leg onto the arch and cut the bulk of the material off at the band saw. Then, using a hand plane and multiple test fits, I refined the angle until it fit snugly at both the top and bottom.
Once I was happy with the fit, I rounded over the ends at the disc sander.
Through Mortises
I did a little layout for the placement of the crosspieces and transferred the angle from the arch to my cross support pieces.
I laid out the through mortises and hogged out the bulk of the material at the drill press. Then I started chiseling toward my layout lines. As I chiseled closer to the line, I paid attention to the angle I was holding the chisel and matched it to the angle of the arch.
Working from both sides and doing a few test fits, I snuck up on the fit little by little, refining as I went until I had a nice tight-fitting mortise all the way around.
I cut it to length and repeated the process for the rest of the cross braces.
Assembly Time
It’s easier to sand everything before assembly, so I wrapped the leg in tape so I wouldn’t get any glue on my freshly sanded surface.
Once I got the leg glued up and in place, I drove the walnut wedges in to secure everything. After the glue dried, I flush-trimmed them with a pull saw and cleaned it up with a block plane.
When freshly milled, mahogany has kind of an ugly pink hue to it. To get it back to that rich look we’re all used to seeing, I used some water-based dye to darken it up and pop the grain.
Before assembling the arch, I prefinished all the parts.
Reinforcing the Rock
The final step before assembly – I decided to fill the void I’d carved in the rock with spray foam. The rock had a natural crack in it, and after removing the bulk of the interior structure, I wanted to make sure it didn’t come apart. The spray foam fills all the nooks and crannies and is extremely sticky, so once dry, the shell of the rock should always stay stuck in place to the foam.
I filled it up little by little so it wouldn’t over-expand and break the rock apart. Once dry, I flush-trimmed it off with an old saw.
I covered the bottom with felt to protect the floor and trimmed it to the shape of the stone base.
Final Assembly
It was finally time to assemble all the pieces. I used a slow-set epoxy so I’d have plenty of time to fiddle with the fit of the arch and make sure everything was tight and aligned perfectly.
Since the arch was a hard shape to clamp, I used screws to hold it in place while the glue dried. I then came back with some dowels to plug the holes and add a little decorative feature.
Of course, down to the last detail, as I drilled out one of the holes, a piece splintered off. No big deal though. I used some CA glue to glue it back in place, flushed it up with a chisel, drove home the dowel, sanded it, and touched up the finish.
The last thing to do was bolt it to the rock. It’s really easy to over-tighten and strip out wood threads, so I generally only tighten until the washer stops moving. This ensures I don’t strip the threads and that there’s enough give for the wood to move without splitting the top.
Wrapping Up
Thanks for sticking with me through this whole build! This project really pushed me out of my comfort zone, combining traditional woodworking techniques with something as unpredictable and organic as a granite boulder. It’s definitely one of those pieces that makes people do a double-take.
If you’re interested in seeing more projects like this or want to check out what I’m working on next, I’d love to have you along for the ride. And definitely check out my friend Eric’s channel, 30×40 Design Workshop – he’s doing some incredible work in architecture that continues to inspire my own designs.
I’m the owner of Benham Design Concepts, a mixed media art studio where I design and build custom furniture and other works of art using wood, glass, stone, and various metals.
In this blog, I talk about the art I create, my journey, and the things I learn along the way.