Installing insulation boards over a Wooden Subfloor
Ultralight boards are typically installed over concrete slabs with thinset. While they can be installed over ¾” plywood, it is mostly beneficial over cold/unheated subfloors (basement slab, drafty crawlspace, room above the unheated garage).
Ultralight is installed “red-side-up” and is typically covered with our StickyMat or DCM Pro heating systems. Those can then be tiled over right away. You can also apply other floor coverings by first applying a 3/8” layer of leveler.