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 true moisture barrier.
Why Use It? Where Did It Start?
Rosin paper was originally used as a protective barrier on wood subfloors not for moisture, but a method installers used years ago 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 subfloors.
Asphalt felt paper is installed by rolling out on the subfloor before installing nail 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.
Manufacturers and Warranties! Be Careful
Today, practically all manufacturers follow to some degree what the National Wood Flooring Association (NWFA) recommends. And one of their recommendations is the use of asphalt felt paper over wood sub floors. Nowhere do they mention rosin paper.
The problem with using rosin paper or some other paper the handyman mentions is what happens in the case of product problems. Manufacturers can be brutal when it comes to who is at fault with problems. Unfortunately most of the time they’ll blame the installer. Regardless of the fact, by not following a simple recommendation of using felt paper may void any warranty you may think you have. Even if the problem was not a result of the wrong underlayment! This issue is more common with prefinished manufacturers. Go figure.
How About Plastic Film or Visqueen?
These products should not be used on wood subfloors as they only serve to trap moisture and can lead to mold growth under the right conditions.