sealing seams in laminate tops

It's been a while since I worked with laminate, but I do the same as Dave. I built a jig that will cut both pieces at the same time for a perfect fit. I think the biggest concern is where those seams are placed, i.e. near the sink :no:

The contact cement will seal the substrate to a degree, but repeated exposure to moisture will eventually cause problems.

It's about 19" by 40". The second pic is a bit blurry, but it shows a rubber washer there for gripping the pieces. The dado in the center is lined with laminate so the bearing has a smooth surface to ride along. You butt the two pieces together and line them up (purpose of the black lines) and rout both pieces at once riding tight to one side of the dado or the other. As you may know, this isn't for postformed work.

I haven't done any postformed work, but I don't see why you couldn't run a bead of silicone at the top of the joint and glue the rest before clamping. It would be better than nothing.

Sorry, I can't take complete credit for it. It was a seaming jig that I first saw in Herrick Kimball's "Making Plastic-Laminate Countertops." I can only take credit for the fabrication using my carpentry skills to build it. But, it is a great jig and has served my purposes well.

And, there are many countertops that need a sheet larger than 5x12, so seams are unfortunately necessary.