Building a New Roubo - Split Top v Standard

[Joshua Lucas]

Let me make an argument in favor of a split top, especially if you are going to use a green slab for the top.

I bought a 3.5" x 23" x 7' (well, 10', but 3' got used for the legs) white oak slab about 5 years ago for my bench top. At the time it had been air-drying for about a year and was around 25% moisture content. I let it continue to dry for another year, which is to say that's how long it took me to get around to building the bench. By then it was probably 20% MC. Initially I had planned to make a solid top, but in the intervening year it had cupped considerably so that the center of the slab was probably an inch lower than the edges. I dealt with this by sawing the slab in half and making a split-top bench.

When I built the bench the split was a bit under 1.5" wide so I made a filler out of a 2x6. In the four-ish years since then the gap has grown to a hair over 2" - more than half an inch of movement. If the top had been solid (ignoring the issue of the cup) it would have either warped the base considerably or, more likely, split badly down the center. However, since the top is split, the only problem is that I need to make a new filler.

I don't use the split for anything - clamping, tool storage, or otherwise - so I wouldn't miss it if I were to glue in the filler. I probably won't do so though because while the top is mostly done moving, it may never completely stop.

As far as keeping the tops coplanar I haven't really had an issue. I re-flattened it once a couple years ago and haven't needed to since, though it probably wouldn't hurt to do it again. Of course any slab top, especially a green one, is going to need flattening every year or two. It probably helps that my tops are from the same slab and are mostly quartersawn.

In short, I'm very glad I went with a split top because green wood moves a lot.