I have a problem with a laminate floor, laid about one year ago. The
sub-floor is conventional floorboards with wet underfloor heating on top and
then a recommended underlay.

In one place in the kitchen there seems to be damage to the t&g join and one
plank depresses if weight is put on it:

http://bertcoules.co.uk/non%20websit...roblem%202.jpg

(short version: https://tinyurl.com/yam3sdah )

The flooring runs under the kitchen units all the way to the wall. A
laminate fitter examined this and suggested that rather than lifting and
replacing the plank it would be possible to drill a small hole, squirt in
expanding foam and then weigh down the floor until it had set.

I was OK with getting him to do that, but then he had second thoughts about
drilling the hole. "There's too big a risk of hitting the pipework" he
said.

What do people think, firstly of the suggested method and secondly of the
dangers of drilling into the laminate? I'd have thought that going
carefully and using a depth gauge (and perhaps a non-pointed bit?) it ought
to be all right.

Also, any thoughts on what might have caused the damage in the first place?

Many thanks.