Standard foam underlayment does not provide a moisture barrier between the sub-floor and the laminate or engineered hardwood flooring. Hence, a standard foam underlayment can only be used in situations where there is no potential for any moisture travelling from the sub-floor and into the finished flooring material. Standard foam underlayment should only be used on plywood sub-floors that have a basement or on above grade concrete floors, that are common in high-rise condominiums. Plywood floors that have a crawlspace below them should always use an underlayment that has an integral moisture barrier or as an alternative the installation of a separate plastic moisture barrier to avoid the potential of moisture damage to the laminate or hardwood flooring.
Figure 3 - Moisture resistant standard foam underlayment
In summary standard foam underlayment can be used in above grade plywood and concrete sub-floors, providing that if there is a crawlspace below a plywood sub-floor it must be protected with a separate or integral underlayment moisture barrier. If a high level of sound attenuation is required, which is common in multi-unit dwellings, the standard foam underlayment will not perform adequately.
Standard Foam, Moisture Barrier Combination:
Where the installation of the underlayment requires a moisture barrier most manufacturers have produced a combination standard foam, as previously described, with an integral plastic film adhered to one side (Figure 3). While there are numerous different trade names for the products they are all basically the same material and have the same advantages, disadvantages and inherent quality levels. Having the moisture barrier prevents the potential of moisture entering the laminate or engineered hardwood flooring from below.
The standard foam with integral moisture barrier underlayment is sold in rolls, the most common being 100 sq. ft. and as with the basic standard foam underlayment larger rolls are available for commercial and professional installers.
The sound attenuation, enhanced comfort and its ability to eliminate sub-floor inconsistencies are the same as the standard foam product - very low.
Note: The recommended thickness of polyethylene for a moisture barrier is 6 mil. Very few of the standard foam with integral moisture barrier products have 6 mils of plastic adhered to them. Many of the manufacturers will advertise their underlayment as being moisture resistant, rather than stating that it serves as a moisture barrier. Hence, the ability of this underlayment to actually protect the laminate or engineered hardwood flooring is debatable.
Note: As with any moisture barrier, the installation of a standard foam underlayment with integral moisture barrier to provide proper moisture protection to the laminate or engineered hardwood flooring is totally dependent upon its proper installation. If it is not installed properly it serves no purpose what-so-ever.
Floor Muffler™ Underlayment:
Figure 4 - Floor Muffler™ underlayment
As previously mentioned technology in floor underlayment does not stand still. One manufacturer has created a somewhat unique product that is sold under the trade name of Floor Muffler™, (Figure 4)
One of the problems with either laminate or engineered hardwood floating flooring is that when walked on it produces a very hollow or echo type sound. The Floor Muffler™ underlayment has been engineered to all but eliminate this problem. Using a specially designed closed-cell foam with an integral moisture barrier, the product is considered the Cadillac of underlayment. Table 1 details the benefits of the Floor Muffler™ underlayment.
Benefits of Floor Muffler™ Underlayment.
- Moisture permeability specifications exceed recommended values for installation over concrete slabs
- High degree of sound attenuation for both reflective and through floor instances.
- Eliminates 95% of the hollow or echo sound
- Can be used on plywood and concrete sub-floors
- Less expensive than cork flooring
- Provides finished floor stability
- Provides walking comfort
- Eliminates most sub-floor inconsistencies
- Provides thermal floor insulation
- Very durable
Another advantage of the The Floor Muffler™ underlayment is that it has a self sealing overlap system. This overlap system saves a lot of time and labor installing it. For any moisture barrier to work properly and perform the function it was designed for, all of the joints must be sealed to one another. Not to do so will allow moisture to penetrate the barrier along the seams, which has the potential to damage the finished flooring.