Quick Menu Prepare Your Project Can I use other Warmup Heaters with the Underlay/ Dual Overlay? How is Dual Overlay sold? Installation Heater Is the Dual Overlay fixed to the subfloor? What are the Dual Overlay board made from? How do I cut the Dual Overlay boards? Can the Dual Overlay be used in wet areas? Compatibility What flooring can the Dual Overlay system be used under? Can the Foil Heater be used with Carpet or Vinyl? What are the Dual Overlay board made from? The Dual Overlay is an MDF board with an interactive adhesive that fixes the top board to the base board. See the full technical specification of the dual overlay boards.