Hi, Can anyone advise me on this, I intend to fit (nail) 120mm solid oak, straight onto a solid maple floor, the Maple is nailed onto Joists, the maple floor is flat and sound, been down 30 years, would you advise me of any reason why i should be cautious, I should add the floor size 6mtrs x 14mtrs,
Cheers
Colin.

This will be just fine. you should probably run the new flooring the opposite way of the existing.