Rosin Paper Or Felt Paper?

The question is often asked. What type of underlayment do installers use for nailing down hardwood floors? The consensus varies and seems to have more to do with regional habits or preferences. Additionally, neither of these products offer what many consumers are led to believe; a moisture barrier.

Why Use It? Where Did It Start?

Rosin paper was originally used as a protective barrier on wood sub floors not for moisture, but a method installers could use to keep plaster dust from getting in their eyes or blasting everywhere when a board was nailed in the old fashioned way, by hand. If you're familiar with the fine material that makes up plaster or drywall dust one can better understand the purpose. It also provided a smoother surface to slide boards around on older diagonal laid sub floors. The National Wood Flooring Association (NWFA) offers the use of #15 or # 30 asphalt saturated felt paper or an asphalt laminated paper as an approved vapor retarder. These products are installed by rolling out on to the subfloor before installing nail or staple down products. While overlapping of underlayment on the #15 is often up for debate, the #30 pound product will be too thick for this purpose and should be butted together.