Making a countertop -- questions re; wood

I have an apartment that I will be renting out that is being remodeled. The kitchen will have a pre-made Lowes post-formed Formica countertop.
However, there is a half-wall divider between the living room and kitchen and I want put a small countertop on top of the divider. The countertop will be about 2 feet by 4 feet, and it will have a round end. So, it needs to be custom made. This countertop will sit on top of the divider wall and it will overhang past the wall about 12 to 16 inches, and I will put a couple of bar stools next to it.
Since it will be an overhang that people may lean on, I want to be sure it is fairly strong.
Typically, I think the way people make laminate countertops is to put two sheets of 3/4 inch partical board together and install the laminate on top of that and on the sides. I was thinking of maybe using two pieces of 3/4 inch plywood instead for greater strength. However, I have heard that new plywood can sometimes "cup" or curve a little as it dries out, so I am wondering if that may be a problem. Particle board doesn't do this as far as I know.
So, any thoughts on whether it's okay to use plywood for more strength or would I be better off using particle board?
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BetaB4 wrote:

No, just one thickness is normal. ____________

No, it should already be dry. If you want to use two thicnesses, just glue and screw together. Use yellow carpenter's glue. Use decent plywood too...not the low grade fir from Home Depot; birch from there or luan or virola would be OK. __________

You are better off using plywood, one thickness or two. Since there is a considerable overhang, be sure it is *very* firmly attached to the divider.
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dadiOH
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think corbels. there's no way 2 thicknesses of ply 4' wide will be sturdy enough not to flex enough to cause problems.
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BetaB4 wrote: ...

More than "ok", it's the only logical choice. CD is fine despite what somebody else says it's stronger than the alternatives given unless go w/ _extremely_ expensive which is simply stupid for a laminate counter base.
Normally countertop construction is simply single layer w/ a narrow piece around the outer edge to give the illusion of the extra thickness.
In this case as an overhang the full double-ply would be _a_good_thing_ (tm). As somebody else said, some yellow glue and screw it together to serve as a clamping action "while the glue dries" and it'll be plenty strong enough.
It wouldn't hurt to have a single support on the 16" end in the middle perhaps but it really wouldn't be mandatory--1-1/2" ply will support a sizable load and laminate is quite flexible to just a little bending.
But, as it is a rental and subject therefore to more abuse than normal, a stiffener as also suggested would be cheap insurance.
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dpb wrote:

<snip>
I don't like voids.
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dadiOH
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That's why some folks pay more for cabinet grade or marine plywood.
To the op- I would definitely go with exterior- but if you're anal, you can avoid having to fill any edge voids by using marine grade. [same glue in both]
Jim
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Marine plywood I've used has more plies, is stronger, and I've never found a void. With only two layers it might be a price stand off vs. three of lesser grade plywood. It definitely works up better with nice clean edges. If the strength issue is compelling, a bucks extra cost may save some grief down the line.
Joe
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My countertop overhangs 10" which seems just right for sitting on bar stools. It is made with one thickness of particle board and has worked fine for the last 20 years.
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Thanks all.
I didn't know what corbels were, but I did a Google search and found out. That may be an option. I'll look at the job again and keep that in mind as a possibility.
The idea the two layers of 3/4" plywood may not be enough wasn't something that I had thought about. But, maybe I'd be better off doing 3 layers just in case. I may even look a little better with the edge being a little thicker.
Some mentioned "CD" but I don't know what that is.
I'm assume that no one thinks the issue of plywood possibly cupping a little when it dries out as being an issue. Someone mentioned that to me so I thought I'd check in case that was a common opinion. Sounds like it isn't.
BetaB4 wrote:

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wrote:

Particle board is weaker than ply. Get some 3/4" furniture-grade ply, expensive, but it will have less frustrating voids to tend with, the surface is very smooth and flat (ideal for contact cement). You can apply edge banding or hardwood strips to cover the ply edges. The plys that are the most stable and strongest are those with a lot of layers. You could use MDF but it will deflect under a load. Good luck with your project.
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