Bonding solid-wood table top to plywood base?

[Andrew Wayland]

I'm building a bar top out of cherry boards planed to about 3/4" (really closer to 13/16 to leave room for sanding).

I plan on bonding it to a 3/4" plywood base for strength.

Im curious how you guys would go about this? I was thinking lots of wood-glue spread evenly across the plywood, and then applying the cherry boards to it.... and maybe running a few screws through the back to provide compression while the glue cures?


is there a better/more preferable way to go about this?

[Mel Fulks]

Trying to figure out why it needs to be stronger than just the cherry top. Hope it's dancing girls and not a fight!! Would not glue it to something else ,that could make some small movement turn into big warp. The most I would do is add some cleats on the bottom with slots (instead of round holes) to help strengthen yet allow some harmless movement.

[glenn bradley]

This question gets asked a few times a year. Surface bonding a material that moves (cherry) to a material that does not (or not as much like plywood) generally results in some variation of failure at the first significant humidity swing.

[Jerry Wright]

+1. Don't do it. Just add cleats or an apron structure with expansion slots for screws.

[Andrew Wayland]

Trying to figure out why it needs to be stronger than just the cherry top. Hope it's dancing girls and not a fight!! Would not glue it to something else ,that could make some small movement turn into big warp. The most I would do is add some cleats on the bottom with slots (instead of round holes) to help strengthen yet allow some harmless movement.

hopefully dancing girls!!! I'll have to check with the wife to see if I can raise the ceiling to make room!

Actually; besides strength, the plywood serves to add a lip for a bar rail to set up on.

When we say cleats: what do we mean exactly?

[Brian Henderson]

While there's nothing wrong with adding plywood, particularly to make the top look thicker, it won't add a lot of strength, nor should you bond solid wood to it because solid wood moves and plywood does not. What's wrong with just screwing the plywood to the cherry from beneath, using elongated holes in the plywood to allow wood movement?

[Mel Fulks]

A cleat would be a piece of wood ,probably no more than couple inches wide , going in opposite direction from the cherry top .Just a cross brace.

[Andrew Wayland]

That should work I think... I just wanted to provide the maximum amount of strength possible, since there's a good 12" overhang.

So: how does this sound then:

1: I screw the plywood base directly into the cabinets.

2: I pre-drill holes through the plywood at certain intervals (16" or so?)

3: I use cabinet screws (or another wide-head screw) to go straight into the cherry top from underneath?

I think thats what we're getting at? Giving g the screw lateral movement through the plywood?


And should I consider silicone caulking at all to provide extra adhesion? Or just rely solely on screws?

[Andrew Wayland]

A cleat would be a piece of wood ,probably no more than couple inches wide , going in opposite direction from the cherry top .Just a cross brace.

I don't know why I'm having such a hard time visualizing this? (I guess it shows how much of a rookie I am here).

When I think cleat, I think of a piece of wood attached to the wall to provide support.

do you have a picture or example of what you're talking about? I appreciate the help!

[Mel Fulks]

Maybe "at right angle to cherry top" is more accurate.

[David T gray]

https://www.google.com/search?q=cleats+for+table+top&rlz=1C1ASRM_enUS721US721&biw=1920&bih=974&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjN6aC8uJ3SAhVJKyYKHU1ZDOMQsAQIQA#imgrc= NDduPJ2cxvkAbM: u can also do a sliding dove tail if u want to go fancy :)

when u do it u want to make the cleat tight to the wood but also be able to move so a oval hole in the same direction as the woods width

[Andrew Wayland]

Okay. I see now.

I dont think I can make that work for my application, due to height restrictions. Now I'm wondering what I can do to make this project work!

[David T gray]

take a picture of what u are trying to do.

[Jim Becker]

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.

[Andrew Wayland]

take a picture of what u are trying to do.

354367

Essentially I have the sub top and the actual top. The sub top is plywood and the actual top is cherry planks glued on edge to make a single panel.

I was going to glue the sub top and cherry top together, but I'm finding now that it's a terrible idea (good thing I checked first!!!).

So now, I'm thinking I should glue and screw the sub top to the cabinets. Then I can use screws and washers to attach the top to the sub top?

[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.

http://i1092.photobucket.com/albums/i414/yo-andrew/cstar-table-1_zpsa96860b2.jpg