If installing over a crawl space, a layer of 6 – 8 mil plastic should cover the entire ground area. A vapor barrier laid between the hardwood and plywood is not enough to prevent moisture reaching the hardwood. The crawl space should be heated to the same temperature as the living space.
Open vents must be installed to provide adequate air flow. Hardwood flooring products vary – some are stable in this situation, some may not be usable. At BC Hardwood, our wood experts can help you choose the best solution.