Moisture Barriers For Hardwood Floors
Today moisture barriers (retarders) are being looked at more seriously as our focus is more on the appearance of hardwood floors over traditional functionality. It’s important they be considered retarders only as the environment indoors and out can affect the performance of any hardwood floor. There are also different applications discussed below.
For instance, wood floors over concrete require an impermeable barrier. Often plastic sheathing is mentioned by most manufacturers. Sheathing comes in the form of rolled plastic (also called visqueen in the construction trade). For the most part a 6 mil thickness is suggested.
Concrete Sub Floor Moisture Barrier
The application is accomplished by laying out the plastic across the installation area. While installers differ on exactly how with some taping overlapped seams, the general use is to prevent moisture from affecting the hardwood flooring after installation. Note; this application does not protect from major water damage such as washing machine floods and plumbing failures. The purpose is to prevent small amounts of prolonged moisture migration from affecting floors.
You may be wondering; “how am I supposed to use this stuff with a glue down floor?” This procedure was never intended for these installation types. However, an older less used process utilized a thick black mastic where the sheathing was then laid into.
Nowadays solutions for glue down installation on concrete call for the use of a trowel spread barrier. You may notice the original glue down pages on the site never mentioned a moisture barrier as they were written before the widespread usage of newer applications.
Wood Sub Floors
For wood sub floor installations, plastic sheathing should not be used. Why? Over time it can trap moisture that can eventually lead to mold conditions between the hardwood and sub floor. It also traps moisture that can cause sub floor rot over time. Instead basic roofing paper is used, which does offer breath ability while allowing some air flow and does not promote mold growth.
While there are other forms of protection being used, most installers use common roofing paper for wood sub floor installations. If in doubt, I urge following the individual manufacturers recommendations as warranty coverage can often be voided by not doing so.
Vinyl proves to be an excellent barrier and has often been used as a moisture barrier when gluing to subfloors with questionable moisture content. In recent years hardwood adhesive manufacturers have developed sealers to be used in conjunction with both direct glue down installations and nailed or stapled floors.