Expert: Bruce E. Johnson - 2/4/2011

Question
I believe our cantilevered floor was not constructed properly.  The cantilevered floor extends out the back of our house.  The bottom of it is covered with perforated soffit.  When I was investigating a cold draft coming up through our master bathroom floor vent (on the exterior wall of the cantilevered floor), I noticed that I could see around the duct work to the area below the floor vent.  I saw some insulation and some open space to the perforated soffit below, and daylight.  This didn't seem right, so I checked the blueprints.  It appears that the area above the soffit should have been sealed with 1/2" ext. grade sheathing, as well as insulated with R-30 insulation.  I don't understand why this area of my house would require ventilation.  Thank you for your suggestions.

Answer
Hi keith, If what you say is true then you are right.  You need to pull the vented soffit material down, insulate, and then install either a Hardipanel material or an exterior grade plywood or densglass drywall to seal  the area off.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com