Durock 1/4" x 3' x 5' EdgeGuard Underlayment, $11.99 USD/Box, LL Flooring (Lumber Liquidators)

Durock 1/4" x 3' x 5' EdgeGuard Underlayment is ideal for floor and countertop tiling projects. Lightweight, 1/4-inch thickness helps transition smoothly with carpet or wood flooring. It is easy to cut and secure, water-resistant, and mold-proof, ensuring durability without rotting or warping. The smooth edges are perfect for installation.