Moisture from drywall mudding, painting, wet sheathing and wet studs etc. will always migrate to drier materials. For example, from an unheated crawl space, moisture will quickly absorb into dryer plywood, pass through it and occupy the next driest material which is usually hardwood.

The hardwood will be the first, and likely the only, material to visually show the signs of migrating moisture. The best way to tackle moisture problems is to plan ahead and take the necessary precautions and tests to ensure the correct site conditions exist before flooring is delivered to site. Testing accurately for moisture can only be done using good quality testing equipment.