Underlayment for Laminate Flooring

Q. What type of underlayment is required to install laminate flooring?

A. Laminate floors should always be installed over a moisture-proof membrane, such as polyethylene sheeting, and a cushioned foam underlayment. Some underlayment products are composed of foam with a waterproof backing, combing both in a single solution. In general, cover the subfloor with the polyethylene sheet, overlapping the joints by 2 in. and sealing the seams with duct tape. Then, lay the foam underlayment over the plastic sheet, butting the seams together and seaming with duct tape. (Avoid overlapping sheets of foam underlayment, because the double thickness will cause problems when you lay the boards.)