Why do wood floors fail?

 
It must first be determined what constitutes the failure.
 
Once I was looking to build a wood floor that would finish to dark reddish brown. I chose Brazilian Walnut. To get added strength and resistance to indentations (high heel shoes, wheel marks), I chose wood that was quarter sawn. Little did I know that when this wood is quarter sawn it exposes a vain that when stained turns yellow. Some people think this beautiful (like Me). But, not the client I built this floor for. In their eyes the floor failed.
 
There was a lovely home built on the bluffs overlooking Malibu Beach. It had large glass doors the full width of the house facing southwest. The flooring contractor installed a solid oak plank floor in accordance with the industry standards. The floor cupped badly. The floor had failed. My investigation found that there was a 35º difference in the temperature of the room from ceiling to floor during the day. The sun was so strong that it was cooking the wood, causing it to expand.
 
As wood floor experts, it is not only our job to find out what went wrong, but, to predict what might go wrong in a future project.
 
Moisture vapor is the first suspect.