I installed pre-finished maple flooring in my cottage in January over an unheated crawlspace with a concrete floor and a vapour barrier on the underside of the subfloor. At the time of installation the humidity was about 60% in the living area and now it runs around 68%. Over one week period in July the flooring "bubbled-up" in an area 4 feet long and 3-4 boards (12 inches) wide, raising it about 5/8 inch at the worst spot. I checked for water from the kitchen and it was dry. I left lots of room around the perimeter for swelling and the problem didn't occur until six months after installation. Any suggestions on how to eliminate problem and correct the present situation?
Your problem is definitely moisture. First, the subfloor should not have in excess of 5% moisture. The pre-finished flooring would have to be stored in the room for 2-3 days with the boxes open and the moisture not exceeding 50-53% relative humidity before laying. Your problem should be attacked by reducing humidity with the installation of a Humidex unit. Call 1-800-416-9111 for more information.