Combination Foam/Film Flooring Underlayment

What is it? – Combination foam/film underlayment is essentially the same as standard foam except that it has a moisture barrier attached to one side. The moisture barrier prevents moisture from getting into the flooring from underneath and potentially causing major damage. As with the standard foam, manufacturers may offer combo underlayment under their own specific brand names, but the quality is fairly consistent. The thickness is the same as standard foam, and so is the level of sound reduction, comfort, and sub-floor correction. Also like standard foam, combo underlayment is sold in various size rolls, depending on the manufacturer. Because of foam/film’s limited level of sound reduction, it should only be considered for base grade, or entry level, use. Where is it used? – Combo underlayment is used wherever there would be the possibility of moisture coming up from the sub-floor. Most of the time this would be on the ground level when the sub-floor is a concrete slab. As previously mentioned, if you have a plywood sub-floor that is over a crawl space, the combination foam/film underlayment is highly recommended to preserve your flooring investment. Note: While it is very rare these days, some manufacturers may not offer the combo underlayment. If you need moisture protection, but the manufacturer does not offer this type of underlayment, then you will need to lay 6mil plastic sheeting down first then install standard foam underlayment over it. The 6mil plastic is acceptable to most manufacturers, but to be sure it will not void your warranty, check with your specific flooring manufacturer before using this method.