All wood products are affected by environmental conditions, especially prefinished materials.
To control wood movement- expansion or shrinkage- it is recommended to acclimate the new flooring in the areas to be installed, not in (garages, U-Haul trailers, sheds, or tents) to normal lived-in conditions while in the boxes. If the products are protected in plastic then open the ends of the boxes. Length of time is not the determining factor. The goal of acclimation is for the core of the product to reach an equilibrium or moisture balance of the new flooring with its surroundings before installation or fastening. This balance could be achieved in as little as 1 to 5 days, or longer for some dense or oily exotic species.
Avoid shocking the floor.
Just like you, wood actually performs best with consistent indoor temperatures of 60°-80° F and indoor humidity levels of 30% - 50%. Very dry or humid regions of the country usually require extended conditioning. Maintaining the recommended acclimation levels even after the installation should be viewed as ongoing floor care. Your doing so will help to minimize board movement, excessive squeaks, finish cracking and gaps.
Hygrometers sold in most Target and Wal-Mart stores ($10-$45) can be used to easily identify the need to regulate the humidity or air moisture.
In addition, to prevent board warping or bowing, do not cut the plastic support bindings on the outside of the packaging until ready to install. Store products flat, in a dry place. Provide air flow under and around cartons. Do not store directly on bare concrete or next to outside walls. Cartons should be placed as close to the center of the installation area as possible.
Proper jobsite conditions, acclimation and moisture testing of the subfloor along with the new flooring all works together for the success of the installation and is the responsibility of those overseeing the project.
A vapor barrier is needed to protect the new flooring against moisture or moisture vapor.
Answered on 3/11/2013 by cc-2