I would check the bond between the strip underlayment and the bottom of the top, then check the bond between the underlayment and the top of the cabinets. Dime sized dabs of silicone every 18" or so.

Your installer probably did what ours did and just sat it down on top of a few strips of wood. I can pick up the whole countertop on my peninsula. Since the wood strips were placed sporadically, after a few months the countertop started to become wavy and out of level. The installer refused to fix it and although he was a DuPont certified installer, DuPont would not do anything about it. I will never have Corian again. I recommend you have it checked soon.

fedupwitchu:

Corian is installed on strip underlayment only. It should be continuous and siliconed to the top and to the cabinets with dime sized dabs every 18". If yours isn't, that's fabricator error, not the fault of the Corian.

Thank you all for these comments and suggestions, they are very helpful. A manager from the design center that subbed out the job to a Corian installer and fabricator came to look and listen to the problem counter today. He was non-committal, despite witnessing the shaking and loud drumming noise from just a slight pounding to the counter! But he agreed that a Dupont/Corian "somebody" has to make an inspection to weigh in on the situation. I didn't mention this before: There's a counter overhang for chairs. The first time I looked underneath my new Corian counter I was stunned: you see strips of plywood and shims for the underlayment. It looks like a set of cheap supports and frankly amateurish, nothing like my previous Corian counter. So far I'm very disappointed in my new Corian counter; I'll keep you posted on whether or not Dupont/Corian and the design center make good on a bad situation.

Noname Online:

We need to see a picture please. I just did this Corian re-installation with 1" aluminum square tube "strip underlayment":

This may look like "cheap supports" and "amateurish", but in fact is superior to solid underlayment and compliant with DuPont installation standards. Solid underlayment traps heat and each of these "strips" had to be individually adjusted/shimmed to level; not possible with solid underlayment.

Here's the underlayment for my problem Corian countertop. This is the only area with a counter overhang (for stools), but the other counter sections also have the same shaking and shuddering noise problem. Observations and suggestions are welcome.

That doesn't meet DuPont's installation instructions. The plywood across the front is doing nothing structurally; it's just filler whose weight is pulling the top down. That's got to be a 12" cantilever; it needs proper support.

Joseph--can this be fixed without removing the counter? There are two other separate Corian counter sections that also have the shuddering noise and shaking but they do not have overhangs, e.g., a lazy susan cabinet corner. I'm wondering if this entire Corian countertop is a lost cause--cannot be repaired to Corian standards--and should be completely replaced with a correctly built and installed new countertop?

Sure it can be fixed without removing the counter. Mount some knee-knocking corbels and you're done.

The improper cantilever is a large hint that these guys are probably clueless in other areas. Nice seam supports though.

Update: A seam is now visible on the Corian countertop that was not noticeable before. The counter overhang is now not 100% level and is drooping slightly. The rep from the Corian fabricator is coming to inspect it this week....

N O:

You need to find a copy of DuPont's installation instructions and point out the differences between them and what's installed. He can argue with you, but he can't argue with the manual.

Agree, we are working on getting the DuPont rep out asap.

You talk about this type of Countertop.....! am right ?

Freya:

The Einsteins at DuPont, Corian's manufacturer, decided to abandon the perfectly fine brand name Zodiaq for their engineered stone products and instead call it "Corian Quartz". Now it is confusing for consumers to differentiate between the two. Your picture may be of Corian Glacier White or Corian engineered stone. Who knows now?