When having hardwood flooring installed, be sure that your installer uses a vapor barrier- long black paper that comes in a roll and looks like tar paper. It must be rolled out on top of the sub-floor before the floorboards are installed. This will prevent moisture from rising through the floor and causing the hardwood to cup (warp or bow). Also, be mindful that wide planks (boards three inches or wider) are more likely to cup.

Vapor Barrier is particularly important for floors above basements or crawl spaces with dirt floors.

If the crawl space is:

• Accessible- Lay plastic on top of the dirt and place bricks or something heavy around the perimeters to keep it in place. It does not have to be air tight.
• Inaccessible (a previous owner could have built a wall around the entrance) – Assume the worst and be extra-certain that the vapor barrier was laid. Avoid wide planks all together.