Glueing engineered oak floor on wood floor.

[Bigwhite]

I am having my oak engineered wood flooring fitted by a wood flooring company. They said that they will they will ply the already wood floor then glue the oak floor. It is being done in the bedrooms upstairs floor to eliminate any movements or squeaking noises. The property was was build in the 70's so it is not very old and the floors are reasonably level.
Someone said to me that this is not the right method. Can anyone please help.
I would appreciate your comments.
Thanks.

 

[WoodYouLike]

It properly depends on the direction of the new boards: if in the same direction as the original ones, plying over the existing floor is very common - and so is fully bonding the new floor to plywood