OSB for countertop base?

[TomW]

The formica for my new countertops just came in, and I need to come up with some 5/8" plywood to glue it on to. When repairing the rotted bathroom floor, I used 5/8" oriented strand board.

Now I'm wondering how well OSB would work as a foundation for the new countertops. It is easier to come by, and a bit cheaper. I figured on gluing the formica to the "shiny" side of the OSB.

Anyone have any thoughts on the suitability of OSB as a countertop substrate?

I personally wouldn,t do it, even if a customer asked me to. I think that although it's used a lot in house construction now , the only good reason is because it's cheaper and it makes use of wood that couldn,t be used for anything esle. Because it's made from a combination of wood species the expansion and contraction rate isn't consistant. I would use a birch ply. Better safe than sorry.
jack

[fitzjo1]

I would spend a little extra to get it right. I recently built new countertops in my 68. I used exterior grade AC fir. Because moisture damage is so common, I even took the extra step of coating the underside with epoxy. In most cases, you'll probably have more money in formica than plywood, and many hours of labor, too.

Jon in SC

[InsideOut]

OSB is also heavier than plywood because there's more glue.

Shari

[Janets Husband]

Do yourself a favor and use the best plywood you can find (no voids lot of layers) It will be more stable and easier to keep anchored (screws will hold)
Place your Formica then seal the underside.