I’m very confused now due to I spoke with a hardwood manufacturer (BRUCE) and they (technicans) told me this was an approved installation and was even listed in their installation manuals! I trust that the information provided by you is correct therefore I have full intensions to contact the contractor and recommend that he start ripping the floor up. (this happens to be an insurance claim anyway)! Sounds like you are very experienced in what you do.
Thank you again for the valuable information provided.
It matters not what the Bruce manual says, this is not the way to install hardwood floors. Else we would all have many layers of hardwood in old houses. It’s just the cheap way of doing it. The bruce guy was probably reading about installing on old floor boards, and these he has mistakenly thought meant any type of wood. Softwood takes nails well with out splitting, That’s why it is used in all framing and subfloors and sheathing. Any carpenter know this. It’s not rocket science it’s just common sense