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Most Homeowners, Builders, Retail Stores and contractors depend on installers to have the knowledge to properly install their products over concrete and wood subfloors! As an inspector all I ever see is failure! Sometimes it is the manufacturer, the installer or the homeowner not following mfg instructions.
It only takes proper use of moisture meters for concrete and wood that can definitively determine if the subfloor is at the optimum condition to be installed. See additional photos under images.
Most of the the pictures shown depict what can happen when the installer has no moisture meters that can measure moisture content in concrete, wood subfloors and in the hardwood itself. Acclimation is not leaving it in the home for 3 days and then installing it. After that time only measuring the moisture levels will determine if the wood is in an ideal position to be installed. The wood must be within a 4% difference for wood under 3" and 2% for wood 3" and wider. And if your installer doesn't know why this is get someone who does.