Under engineered wood flooring, it is essential to install an appropriate underlayment or subfloor material. The purpose of an underlayment is to provide support, insulation, moisture protection, and sound reduction. Common underlayment options for engineered wood flooring include foam or cork underlayment, plywood or OSB subfloor, and moisture barriers. Foam or cork underlayment helps to reduce noise transmission and provides a cushioning effect, enhancing the comfort underfoot. Plywood or OSB subfloor provides a stable and even surface for the engineered wood planks to be installed on. Additionally, a moisture barrier is necessary for areas with high moisture levels or when installing engineered wood flooring over concrete subfloors to prevent moisture-related issues. The specific type and thickness of the underlayment or subfloor material will depend on factors such as the subfloor conditions, desired level of insulation, and soundproofing requirements.