Moisture is the number one cause of problems when it comes to installing wooden flooring. With this in mind it need not be, take the proper procedure to handle it and it will not be a problem. The problem is that a lot of flooring installers do not take this into consideration which can cause major problems.
What quite often happens is that wood flooring is delivered straight to the job site in the winter. The flooring came from a reputable supplier and the wood was stored in a climate-controlled warehouse. After arriving at the job site delays happen and the wood ends up sitting around for a while. Not knowing the affects on solid wood flooring the temperature is increased by the heating in the building. The flooring is fitted and everything is fine, the next winter the customer rings to say that the flooring has gaps between the boards.
The cause of the problem is that the flooring acclimated to the conditions of winter when it first arrived, when it then acclimated to the hot summer humidity it swelled up and the edges of the board were damaged, the next winter the swelling reduced and the gaps were much larger than they should be.