Almost three years have passed since I wrote Part 2 of our series on slab tables. That installment took you through a design exercise performed with two slab sets from different trees. Unfortunately, we’ve been busy, busy, busy since then and the slabs are still leaning against our wall. But we recently completed a job that is a perfect example of how to design and build a slab table. The finished tables are spectacular. So now I’ll take you through the construction process we followed, to illustrate some of the finer points of building large boardroom tables with solid slabs of wood.
Let’s start with a brief look at the project. A local financial firm was moving into a new headquarters and wanted a drop-dead gorgeous boardroom table, and a matching smaller table to go in another meeting room. The owner really likes the live edge look. We were told that the larger table needs to seat 18 people, and the smaller table needs to sit 12. After analyzing the room, we recommended that the larger table be 20 feet x 5 feet wide, and the smaller table 14 feet x 4 feet wide. The larger table needs a significant amount of wiring, while the smaller table needs no wiring.
We decided to take a look at slabs and then come up with a table design. Or maybe we decided on a table design and started looking for slabs. Both of these steps usually happen simultaneously – you have an idea of what you want to do, you see what wood is available, and then you rethink what you want to do. We looked at several sources and ended up buying slabs from GL Veneer in California. They have a great website with easy sorting and decent pictures (with dimensions) of their current inventory.
The addition of power in the large table suggested a particular approach to the table top. We like to put power/data units running down the center of the table. And we also generally favor having smooth edges on our tables – they are much more user-friendly. So we decided that the big table would be made from a set of slabs trimmed to straight lines on their outside edges, with the live edges framing an opening in the center of the table that would house the power/data units. Like this:
This arrangement has the added bonus of allowing us to make a large table without using slabs that are so huge that they can’t be moved. We have to get this table into the boardroom on the second floor.
The smaller table was narrower and didn’t need power, so it was feasible to do the top out of two wide slabs placed end to end, like this:
In both of these renderings, we used photographs of actual slabs to make a Sketchup model of the table and room. This is the same process described in Slab Tables Part 2.
Ordering from GL Veneer was easy. They did a nice job packing the wood for shipment. We ended up paying $16,535 for 6 slabs (including freight to PA). If you are used to buying raw lumber, that works out to about $28.50/ board foot. Which is quite a bit more expensive than ordinary walnut lumber in the same thickness, which usually runs us about $12/board foot.
The wood doesn’t look like much when it arrives:
It’s actually really beautiful wood with great figure. That will be revealed when we complete the process of flattening the slabs, sanding them smooth, and finishing them.
It’s not apparent from the photos, but the slabs are not flat. Not at all. There is an overall curve of at least ½” over the length of every piece, and there are bumps and valleys in random spots as well. You can see this when we put the slabs onto the bed of our CNC router:
When the tree was sliced up, each piece was consistently straight and flat. The process of kiln drying puts the wood under stress. As it dries, it settles into a different shape which is rarely as flat as the initial cut. We’ll need to reshape each slab in order to end up with flat and smooth table tops. That is a challenge in itself, but to make it even more difficult, every time we remove wood from the slabs their internal stresses cause them to bend some new way. Flattening these slabs will involve repeated trips to our CNC router, with a small amount of stock removed each time. We’ll let the wood rest for at least 24 hours after each machining operation.
When we start the machining process, the router is only removing stock on the high points. Here’s how that looks:
This slab has its high point in the center on the right side. We have 8 of these slabs to flatten. It takes a good long while. The machine has to be run at a relatively low speed in order to make sure we get a clean cut:
The machining process removes the rough surface left from the sawmill and we can start to see the beautiful grain of the walnut. Here’s a closeup, showing both the milling marks left by our router and the incredible curl and flame grain:
Once the slabs are flat, we can begin work on the cracks and holes in the wood. There are lots of these. They all need to be filled with epoxy. This requires multiple pours, as the wood soaks up a lot of the epoxy. Sometimes it runs out on the floor, and we have to build a little dam to keep it in place:
This slab had by far the fewest holes and cracks. All of the others had a lot more to repair. More labor hours.
Many of the slabs have large cracks running through them. We stabilize these using an inlaid butterfly. Lots of woodworkers choose to put these on the top of the table because they do look cool. We decided that we’d rather flip our slabs so that as many of the cracks as possible are on the bottom, and then to put in butterflies to keep the cracks from propagating. We cut the butterflies on our CNC. Here’s a shot of one being glued in:
We ended up doing 28 butterflies in our 8 slabs.
The final steps for the epoxy and butterflies is trimming and sanding them so that they are flush with the wood. This involves work with a router and sanders. Here’s a closeup shot of one end of one of the slabs, showing the extensive repair work:
While all of that work on the slabs is proceeding, we’ve been working on the steel base. Our engineers drew up a set of plans that have all of the features we want. It’s common practice when inexperienced woodworkers make slab tables, to simply bolt the legs to the wood. That works OK if the wood is flat and the table is small. Our tables are going to be quite large, so we need to be able to disassemble the base to move it. We also want our base to be structurally sound on its own, without the wood. And we need to run wires through the base and to the top of the table. So our bases are considerably more complex and beefier than the usual approach.
We have the laser cutting, and some of the welding, done by a specialist steel fabricator. We take those parts and do a little more shaping, drilling, and welding. Each base consists of leg units, made of 2” x 4” steel tube, and bridge units made of ¼” steel, that connect to the legs. All of that is capped with a ¼” steel plate, pierced and drilled for power/data units and for the wood slabs. Here are some shots of the connection between the bridge unit and the legs:
And a completely assembled base:
The central base units have openings to the floor for wires and removable caps for access to the wire channels. There are levelers in the bottom of each leg unit:
Next, we start making the cuts where the slabs will meet each other. The smaller table is simple: just make a perfectly straight cut where the ends butt together and then blend the edge where they meet. Of course, two slabs are not going to mate perfectly without a little persuasion. We start the blending process by putting the slabs on a cart, just to get a sense of what needs to be done:
Slabs cut from a single tree are never of identical size. That can make blending the edges where they meet an issue. Fortunately, we’ve been able to trim the two slabs for our smaller table to the same dimension. We’ll need to do some artful shaping of the natural edge to make a smooth transition. The ends present a different problem. Those sharp corners are going to be a constant source of irritation for users trying to walk around the table. If we leave them as is, somebody will end up with bruises. So we’ll do a very heavy rounding job at those points.
The blending is all skilled handwork, with a variety of wood shaping tools. At the end of that process, the table tops look like they always belonged together:
Note that the live edges appear to meet as if the trees grew that way, and that the sharp corners are now much friendlier. This table is ready for the finishing room.
The large table is a much more complex problem. We’re trimming the slabs so that the perimeter of the table forms a perfect rectangle, and leaving the live edges running down the center of the table – the “river” configuration. We’re not going to fill that void with epoxy, as that would make a permanent bond between all of the pieces. It would be impossible to move something that size out of our shop. Instead, we’re going to blend the live edges along most of their length, and fill in the gaps at each end of the table with smaller pieces that have been shaped to match the grain pattern on the larger slabs. This is very tricky. We want to use our CNC router to make perfectly mating seams. The seams are not straight – they wander here and there, following the natural grain lines. We need to make multiple test cuts on scrap material to make sure the fit is perfect. And, thanks to the programming skills of our engineering team and the fabrication skills of our shop floor team, the finished seams look great:
Here’s the whole top. This is fabulous walnut, with a lot of grain action when seen from far away and even more when you get close up:
We will be rounding these corners and easing all of the edges on this table, too.
Underneath the table there’s a lot going on. We had to set the top slightly skewed relative to the base in order to get the open river section to reveal the power/data ports. That makes this photo look a little weird:
Note the pockets for special joining hardware that allows us to assemble and disassemble all of the slabs. Note also the bolts securing the slabs to the steel plate. Each of these passes through a slotted opening in the steel. This will allow the slab to expand and contract throughout the year – as it wants to do. The bolts will hold it flat while that happens.
Applying finish to wood can be very complex – see here for a complete explanation – but slab tables are usually easy. All we have to do is spray a satin clear coat on the wood, and paint the steel black. After that, we bring the tables back onto the shop floor for a final assembly and quality check:
These tables are going to a client located just 7 miles from our shop. This makes delivery much simpler. We blanket wrap everything, take it to the client, and lug all of the pieces up the stairs into the boardroom. What does the finished room look like? Utterly magnificent:
Shoutout to the architect, D2 Solutions. We’ve collaborated with them on multiple projects, and they are always a joy to work with.
I hope after reading all of this that you can see the planning and care we put into fabricating these tables. We used 156 labor hours for the large table, and 95 labor hours on the smaller table. Our approach to making slab tables is not intended to minimize cost, but rather to do all of the work necessary to ensure that the table is beautiful, durable, capable, portable, and a joy to use.
If you have any questions, feel free to contact us.