On Wed, 18 Jun 2008 10:34:14 -0700, noname87 wrote:

I am not a flooring expert or installer

That's quite clear!

but I can give you an
perspective as a design engineer.

The joint have a tongue and grove that must mate up. There has to be
clearance between the tongue and grove to allow the parts to go
together. This will result in one board being able to above its mating
board by the amount of the clearance gap I would expect the clearance
gap to be at least .010 inches. Also the board thickness has a tolerance
(say +/- .005, more likely +/- .010).

[snip]

I installed engineered floor a year ago (DIY, though I doubt that
matters). It's a different brand (Upo). I installed it free floating over
a foam underlayment over a vapor barrier. I do not have the problem
described in the slightest. If there is any height disparity it is
virtually undetectable (I walk on it in bare feet all the time).

You should take a look at some engineered flooring sometime. I think it
would surprise you. Certainly a .010 clearance gap in the groove is way
too high; probably .001 is closer to it. A flexible material like wood
doesn't need the clearance gap that metal does. A manufacturing thickness
variation of .005 is way more than existed with my product. The variation
from the tongue/groove to the surface is the thing that matters (not
total thickness). I'd guess it was probably .001 or less, virtually
undetectable by touch.

Conceivably the OP's variation might have come about with subsequent
moisture absorption. (And if so it may well be an installation error, as
others have suggested.) The material clearly expands and contracts
significantly with humidity, as is explained in the installation
instructions. (Gluing it to a radically different material seems risky to
me because of that, but maybe if the glue remains flexible...) However,
only board-to-board variations in expansion would cause the OP's problem.
Hasn't occurred in mine, at least not to detectable extent.

I can't speak for the quality of any other brand than Upo. But it is
clearly within the state of the art to do much better than what the OP
described.