What material gets put down underneath hardwood flooring to reduce moisture?

Hardwood floor contractor will often use Fortifiber HWD-15 Hardwood Floor Underlayment beneath hardwood flooring.
- Reduces Moisture Related Problems
- Optimum Vapor Permeance
- Excellent Price Performance
- Clean & Easy Installation

"HWD-15 hardwood floor underlayment is an economical and extremely effective Class III moisture vapor retarder specifically designed for optimum performance in wood flooring applications. Consisting of a single layer of kraft paper saturated with asphalt, HWD-15 is a permeable vapor retarder. It reduces vapor flow, without trapping moisture. With little or no asphalt rub-off, HWD-15 is considerably cleaner than other materials, such as roofing felt. It’s also lighter and easier to work with. It aids installation by providing a smoother surface for positioning flooring. Because HWD-15 is thinner, edge laps don’t get in the way during installation of wood strips. It also acts as a “slip sheet” to minimize dust and reduce noise"