Bonding solid-wood table top to plywood base?

[Andrew Wayland]

I wouldn't bond them at all...you'll have a serious wood movement issue when the cherry expands/contracts seasonally and the plywood doesn't. Edge glue the cherry up into a panel, and then fasten to the plywood with screws from the bottom in slots that are in the same direction wood movement will occur in the cherry. Make the screws snug so that the cherry panel will stay flat, but not so snug that the panel cannot expand/contract as it is wont to do.

So I take it I should be applying poly to both sides now?

How much of a slot do you think would suffice? And how many screws would you use? (The top is 20inches deep and 8 feet long).

Finally: in wondering now: the Chicago rail I'm adding said to glue and screw it to the sub top... it's also Cherry. Should I just glue that to the cherry top (like woods... but different sources) and just screw into the sub top?

[Jerry Miner]

Andrew-- I see you've got a couple different threads going on this bar project. I answered the rail question in the other thread.

I think you're getting the idea on attaching plywood to solid wood. I use 1/2" slots, but technically you can use tight holes on the front (rail) edge and ever-increasing slot sizes as you move away from this "fixed" location---as movement will increase as the distance from the fixed point increases. (In a table top or a panel, the "fixed point" is often the center, but in your case, you're better off keeping the movement restricted at the rail--to keep the bar-to-rail joint tight-- and let the top "float" towards the bartender.

The other issue you will encounter--now that I've seen the pic of what you've got-- is the miter. Because wood moves much more across the width than along the length, a wide miter joint will change in angle as the wood moves -- so your tight-right-now miter joint will want to open as the humidity changes. If you can control the humidity in your bar, then you'll be fine. But if there are significant changes in humidity, that miter will present problems.

[Andrew Wayland]

Andrew-- I see you've got a couple different threads going on this bar project. I answered the rail question in the other thread.

I think you're getting the idea on attaching plywood to solid wood. I use 1/2" slots, but technically you can use tight holes on the front (rail) edge and ever-increasing slot sizes as you move away from this "fixed" location---as movement will increase as the distance from the fixed point increases. (In a table top or a panel, the "fixed point" is often the center, but in your case, you're better off keeping the movement restricted at the rail--to keep the bar-to-rail joint tight-- and let the top "float" towards the bartender.

The other issue you will encounter--now that I've seen the pic of what you've got-- is the miter. Because wood moves much more across the width than along the length, a wide miter joint will change in angle as the wood moves -- so your tight-right-now miter joint will want to open as the humidity changes. If you can control the humidity in your bar, then you'll be fine. But if there are significant changes in humidity, that miter will present problems.

Too bad I didn't consider all this weeks ago when I started! I should have just used a plywood top with plenty of finish!

i didn't even put a tongue/groove on the miter, so I guess we'll see what happens

[andy bessette]

One possible way to salvage this could be to completely saturate every piece before gluing with WEST epoxy, so all wood is encapsulated. This should prevent humidity differences from changing the wood dimensionally. I successfully combine solid wood and plywood all the time in a marine environment. Though I would be wary of using 4/4 lumber as a veneer over plywood.

Here is a table assembled from 3/4" birch plywood core, 1/8" teak plywood top, 1/8" Birdseye maple starfish inlay, and solid teak edging, all epoxied together. Measures ~24" x 48". The starfish measures ~13". The solid edging was biscuit joined.