I’m planning to make a breakfast bar top out of old 2-1/4″ oak flooring. I want the top to be thicker, but I’d like the 2-1/4″ faces to show (rather than butcher block style), so the plan is two layers, glue each layer up so I have two 3/4″-thick bar tops, and then face-glue them together. The question is: can I use plywood or MDF for the center of the bottom layer, so the final bar top has oak edges but the middle is oak over plywood? My concern is movement – the ply will be more stable than the oak? And with or without ply, will it be as stable as butcher block style? (I know I’m in for a lot of work jointing everything straight and re-cutting the edges, but it’s such pretty wood — it has the old oak patina — and OK, I’m a compulsive recycler.) – Holly Hamilton
Tim Inman: Holly, I think you’re right on the beam with a plywood core. Also, you’re already acknowledging the wood movement issue, so I think you are 90 percent of the way home on that solution. An important term in furniture lumber is Equilibrium Moisture Content or EMC. Use this to your advantage, and you’re home free. Allow the wood — all of it, including the plywood — to come to equilibrium in the intended environment so the moisture content is the same in all the components before you begin. In other words, let the flooring, the oak and the plywood all spend time in the place where it will live after your cabinetry skills have been performed — or at least an environment very similar. Then, once you’ve built your project, finish it right away. Finishes do not stop moisture from exchanging in the wood, but they do slow down the transfer rate and make equalization and hence, equilibrium, much more stable. In most homes nowadays, the temps and humidity is pretty constant year around. So, the wood should be relatively stable and your project should enjoy a nice long life and give you years of enjoyment.
Chris Marshall: A panel of solid-oak flooring glued edge to edge is going to move across the grain, but the plywood or MDF won’t. That wood movement might not amount to much, but you should still allow for it. I wouldn’t face-glue the solid-wood panel to the plywood. Let the wood move as it will. Instead, I would screw the plywood “core” to the upper layer of solid oak right down the middle, with the screws following the long grain. Then, I’d use slotted holes for the rest of the attachment points through the plywood instead, and drive more screws into those. Arrange the slots so they follow the cross-grain direction of the solid wood. Center the screws in the slotted holes so the oak can expand and contract seasonally. It’s the same way I would attach a solid wood top to a dresser or table.
If you decide to glue up your oak flooring “butcher block” style, so the faces of the flooring are glued together instead of the edges, the panel won’t expand widthwise. Flatsawn wood expands across its grain, not through its thickness. It would take more flooring to make up the same width panel, but in terms of wood movement, it would be more stable, and you wouldn’t need the plywood layer to make your bar top thicker.