Outdoor Dining Table | Concrete and Live Edge

About: The Dogfather, Chris Giffrow Mission statement: Creating custom wood craft and elevating DIYers to next level woodworkers.

A couple years ago I made the notorious Modern Builds patio table and frankly, I did it poorly out of reclaimed decking and it’s the literal worst now. So when outdoor furniture season hit, I went ahead and decided to use the opportunity to do my first outdoor project for my YouTube channel and I wanted to go out with a bang.

I don’t have a full list of everything you’ll need but as a frame of reference here’s some of what I used:

-Glass Fiber Reinforced Concrete Face and Backer Mix with charcoal pigment

-Cedar 4x4’s and Cedar 2x4’s (4x4’s for the legs and 2x4’s for the stretchers)

-Pure Tung Oil

-Beeswax pellets

-Total Boat Halcyon Outdoor Varnish

-1:1 Table Top Epoxy

-Diamond Abrasive Stones and Pads

-A buttload of sandpaper

-3/4 inch plywood (any grade or kind will do, I used scrap)

-Construction adhesive

-6 ¾ inch flatlock screws

-Pan Head Screws

-Silicone caulk

-Paste Wax

-Cake Decorating Fondant Tool

-Simpson Strong Tie Mending Straps

-A variety of woodworking hand tools and power tools (hybrid woodworking ftw!)

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Step 1: Material Preparation

If you’ve seen my video on the live edge box or seen my live edge clock on Instagram, you’ll recognize this spalted maple live edge slab I used for the inlay. It’s been the gift that keeps on giving over the past couple years but this is finally the last of it. I used a track saw to rip one straight edge on the slab and then measured halfway to split it down the middle on the table saw for the split top effect I’m trying to achieve.

I then sanded everything down and used a card scraper to remove the burn marks from the track saw cut. I also used a block plane to break the edges with a small chamfer and drove some screws into the back to give the concrete a little something extra to grab onto.

To seal out the maple, I mixed up some 1:1 table top epoxy and applied it to the wood in two applications, once as a seal coat and the other as a finish coat. The nice thing here is that I’m really just going for one show side, so the side with the screws in it, while still receiving epoxy doesn’t need to be perfect since the concrete is going to cover it. I used a propane torch to break the surface tension and release any bubbles in the epoxy.

After cure, I built the molds, breaking down a 4x8 sheet of melamine with the track saw. It probably goes without saying at this point, but if you don’t have a track saw you can use a circular saw and a straight edge. If you don’t have a circular saw and a straight edge, what are you even doing? Do you even woodwork bro?

I measured the base of the mold directly off the maple inlay so that I have an accurate base and then went back to the table saw to rip some strips for the sides of the mold. Since I wanted a two inch thick top, I went with 2 ¾ strips to account for the ¾ inch bottom and then my trusty cordless hot glue gun to set the long sides of the mold in place. I also cross cut the ends of the mold using a circular saw and a small carpenter square. To lock everything together I drilled and countersunk drywall screws into the ends and sides.

To prep the molds, I rubbed everything down with paste wax and taped off the faces of the inlays. Then I used a cake decorating fondant tool and silicone caulk to lay a caulk bead on the interior corners of the mold. These cake decorating tools are money for getting the perfect corner bead and if you don’t have one and intend on doing some caulking I 12/10 recommend.

After the caulk cures, I peeled away the excess and then wiped the inside of the mold with mineral spirits to clean out the paste wax.

Step 2: Making the Top

Each GFRC concrete mix is different and if you go with standard concrete instead of GFRC you’re going to have to lay rebar or wire mesh and it’s going to be way heavier. This mix starts with the face mix and requires a blend of modifier, water, pigment, and the concrete face mix. We loaded it into a pneumatic hopper gun and sprayed it down into the molds.

Then we mixed the backer which has the glass fiber reinforcement and dumped it into the molds, troweling it smooth and packing it against the walls. It created a bit of a void in the middle but we’ll handle that later with a plywood inlaid substrate.

After popping the mold, I noticed a slight valley where the maple met the concrete, so I went ahead and did a very shallow epoxy pour over the maple again to make sure that the top was perfectly flush. This table top epoxy is self leveling so it filled the valley nicely. After it was cured, I used a block plane and a card scraper to take down a majority of the excess epoxy before sanding.

I then hit the whole top with diamond pads before taking it back to my shop to hit it with a base coat of real milk paint company’s pure tung oil. Pure tung oil can be used as an all natural sealing finish for concrete. I poured it on thick and let it set in before wiping off the excess. I did this process a couple times over a few days just to ensure there was a solid base layer that was soaked into the concrete.

Step 3: The Base

As for the base: this is a four post castle jointed base with a shou sugi ban finish.

If you’re not familiar with a castle joint: it’s a half lapped joint acting as the tenon in a four way mortise resulting in an incredibly strong and stable joint. This base is going to involve eight total castle joints, four on the top and four of the bottom of the base.

I started on the chop saw getting everything to length, namely 28 inch legs out of cedar 4x4s and rough cut 2x4 stretchers. Then I’m setting the miter saw to 45 to bevel the ends of the stretchers for a nice aesthetic and a bit of angular support. Then I just marked out the thickness of the tenon essentially on the 4x4 leg post before breaking out the tenon jig and the dado stack to hog out a majority of the material. To get the rest of the material out, I’m going to use the a bandsaw and chisels, but there’s a ton of other ways to do it, including a jig saw, coping saw, etc.

For the half laps, I similarly laid out my joint and set the depth of the dado stack. Using my miter gauge, a backstop, and a stop block, I hogged out the waste for the stretchers on the top and bottom of the table. Then to fit everything, I added some glue to the inside of the mortises and popped everything together.

I used a forstner bit to bore a hole into the top of the half lap of the castle joint, and then a big ass drill bit to drill a pilot hole for these 6 ¾ outdoor rated flat lock fasteners to make sure this thing is tight and solid. Part of the reasoning behind the fastner is that I wanted to do the shou sugi ban treatment and burn the whole base to a black, alligator skin finish and I’ve got a lot of concerns about cooking glue with an open flame under that high heat.

If you’re not familiar with shou sugi ban, it’s an ancient Japanese wood burning technique that provides great weather resistance to wood. It’s traditionally used on siding but has also been used on furniture. It’s also used, albeit in a different version and capacity, in whiskey making which has the insides of the oak barrels charred to provide rot resistance and flavor. Since this is an outdoor project, this seemed extremely fitting.

To further protect the wood, I used Total Boat’s halcyon outdoor water based varnish. This is my first time using Halcyon so it’s hard to say how it holds up long term, but as far as application, this stuff was awesome. No sanding between coats. I used an HVLP sprayer and if you choose to spray would recommend diluting with 20% water to help lower viscosity per directions. This can also be brushed on with a foam brush and won’t require dilution whatsoever. I sprayed the base with multiple thin to medium coasts as well as a plywood substrate that I would later inlay into the concrete slab with construction adhesive.

Step 4: Finishing Up

After it was cured, I drilled mending straps into the base with outdoor rated screws and fired a pan head screw from the underside into the plywood substrate to attach the top.

As a final seal on the top, I mixed up more pure tung oil with melted beeswax. The beeswax begins to firm up almost immediately on application so I rubbed it in pretty vigorously before scraping the excess with a flexible scraper and then hand buffing off with blue shop rags. I waited one week for a full cure on the finish.

Then voila, you’ve got a table. I really enjoyed this project and the opportunity to experiment with a different medium in gfrc that I’d never worked with before and I love the look of the contrast between the live edge and charcoal concrete as well as the continuous grain pattern of the live edge maple. The base is extra stable, weather resistant, and that deep alligator skin burn is one of my favorite looks out there. Hope you all get inspired to make something cool of your own that pushes you out of your comfort zones.

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