What is the best underlayment for wood floors?
Many times we asked the question what is the right type of underlayment to be used in the hardwood floor installation. The normal products that are always available to a customer are Rosin paper or 15 pound felt paper.
Why would I even need any underlayment in a wood floor installation?
Let me ask you another question why do you even need a moisture retarder or a moisture barrier in the hardwood floor installation?
The answer is very simple: hardwood flooring comes to your house and has a moisture or relative moisture of 6% to 9% maximum. New construction has a relative moisture much higher as high as 25%, due to the many materials just introduced to the the construction that have to do with water: plaster, paint, new wood, plywood, concrete in the basement.
A moisture barrier, or retarder has the function of slowing the absorption of moisture to the new hardwood flooring. If the hardwood floor absorbs moisture too fast it will cause it to expand in a very unnatural way leading to cupping.
So, which underlayment is best suited to retard moisture absorption in a new hardwood flooring installation?
As I was saying before the two main materials available to installers are rosin paper, and 15 pound felt roofing paper. Here is the techical data sheet for Rosin Paper as it appears on the Manufacturer Website:http://www.wrmeadows.com/red-rosin-paper-multi-purpose-building-paper/
RED ROSIN PAPER
RED ROSIN PAPER is a high quality, single-ply sheathing paper, which is widely used in built-up roofing systems as a “first layer” protective barrier. This environmentally friendly paper is manufactured from 100% recycled fibers. The fibers are set in alum to resist bleeding. It is a multi-purpose building paper used as a physical barrier protection throughout all phases of general construction.
RED ROSIN PAPER is useful in a wide variety of construction applications, including roofing, flooring, and as a general jobsite protective covering. When used as an inner liner in wall, roofing, or wood flooring applications, RED ROSIN PAPER acts as a separation barrier, protecting against wind and dust infiltration, while minimizing squeaks. It is compatible with coal tar and asphalt-based roofing systems.
500 ft.²/roll (46.45 m²/roll)Hardwood installers normally used rosin paper, that pinkish paper used as an underlayment. Does rosin paper have any moisture retardant on moisture barrier properties? Not at all.
In the old days rosin paper was used mostly as the dust barrier. You can imagine the old types of plaster, the new construction with this fine dust laid all over the floor and when the installer will strike the nail or install the hardwood floors dust will fly all over the place. That’s why they use rosin paper as the dust retarder more than a moisture retarder. The use of this material became popular and continued for many many years. We always assumed installers are professionals and know why they use rosin paper. But do they? I’ve come to find out that is more of the tradition type of use than a technical or scientific type of use.
More recently I saw installers using 15 pound felt roofing paper as an underlayment. At first it seemeed a counterintuitive type of move. Roofing paper as a flooring? I looked into it in more depth and I really see the value of using roofing paper as an underlayment. Moisture is not trapped is allowed to pass through but at a very slow rate, therefore it does not lead to cupping, it will not lead the hardwood to an unnatural expansion.The National Wood Flooring Association (NWFA) approves the use of 15 pound felt or even 30 pound felt paper as a suitable moisture barrier under brand-new hardwood flooring installation. Will you overlap the joints in felt paper? it’s up to you, but if you use 30 pound felt you will only butt the joints. What about Visqueen or plastic as a moisture barrier under hardwood flooring?
The use of plastic of Visqueen is absolutely not suitable. It will trap moisture and will not allow for moisture to pass through thus creating the right situation for the growth of mold.Some of the other products that are very popular nowadays are Aquabar, Elastilon.