Doug writes from Vancouver, British Columbia: "I am moving my children's rooms to the basement. I would like to lay a subfloor over the concrete floor that is there now. Is it appropriate to build the floor using 1" thick Celfort 300 as the bottom layer, then building the subfloor out of 2x4s and plywood. I will be laying hardwood on top of the plywood. Is the compressive strength of the Celfort 300 sufficient to support heavy furniture placed on the floor if the 2x4s are on 16" centres? Do I need to be concerned about the foam compressing differentially across the floor over time?"

Answer: The description you provide for the construction of the subfloor is appropriate. The resistance to compression for the PINK extruded polystyrene insulating boards is not a problem; actually, you could save some money and opt for Celfort® 200 insulation or Codebord® insulation (4 ft x 8 ft C-200 board) and achieve essentially the same result.