Seam Detailing for a Deep Solid-Surface Countertop

An 80-inch by 38-inch countertop made with 30-inch maximum width solid surface panels creates some head-scratching about where and how to make the seam. May 23, 2007

We are installing Staron solid surface. Putting it over solid birch plywood. Width is 38", length is 80". Max width of surface is 30", so I anticipate a seam running the length of the 80". Is the plywood okay, or do I need to still install the seam block 4" by 80"?

Forum Responses
(Laminate and Solid Surface Forum)
From contributor B:
For the warranty, you need to install the 4 inch by 80 inch ot staron, and I would not install over a full sheet of plywood. Your build up should be anywhere from 1.5 inches to 3 inches wide. For overhangs, I would read the fabrication book.

From contributor U:
I would cut my seam the other way. Two 38" seams instead of one 80", still need power blocks under the joint.

From contributor R:
Unless Staron is different from other solid surface, you shouldn't install over a full sheet... Seams should run perpendicular to the lay. If you can't do that, make sure you have a wavy bit or great alignment tools (vacuum or whatever) for that joint. And yes, you should use a seam block.

From contributor J:
You can use 1/2 inch plywood and double it up with 3" strips around the ends, and near the seams. Basically a framework that accommodates the seam plate. Then you still have a hollow frame that will prevent moisture from building up inside the top. Drill some small pin holes to give it breathing room too. And you definitely want to make your plywood undersize, leaving a gap for expansion and contraction.