What do you put under pergo floors?

What you put under Pergo floors depends on whether laminate or luxury vinyl plank, with Pergo laminate requiring underlayment and vapor barrier, while Pergo Extreme LVP with attached pad does not need additional underlayment in most cases. For Pergo laminate which is HDF core, you need to put underlayment that provides cushion, sound absorption, and moisture protection, such as Pergo Gold underlayment or other foam underlayment with vapor barrier for concrete subfloors, costing 0.50 to 1 dollar per square foot, plus 6 mil vapor barrier over concrete if underlayment does not include it, to prevent moisture damage. Underlayment for Pergo laminate should be 2mm to 3mm thick, not too thick or soft, as too thick underlayment voids warranty by making floor unstable. For Pergo Extreme luxury vinyl plank which has attached pad, you do not need additional underlayment over plywood subfloor, as attached pad provides cushion and sound absorption, and adding extra underlayment may void warranty. Over concrete, Pergo Extreme may need 6 mil vapor barrier per installation instructions if concrete has high moisture, but not additional foam underlayment. Always follow Pergo installation instructions for your specific product, as requirements vary, and ensure subfloor is flat within 3/16 inch over 10 feet.