Expert: Bruce E. Johnson - 9/7/2008

Question
I have an existing sunroom that is on a framed foundation. It is a modualr/panel type sunroom, similar to a Patio Enclosures or the like.  The problem is, I am getting moisture against my slab foundation and odor in the vents (run in the concrete slab)  When the sunroom was added, the pre-existing sunroom was removed and the concrete slab it was on was removed due to excessive cracking. The current subfloor has gotten some rot from mositure being trapped in the fiberglass insulation the installers put in the floor.  The layers are earth > marine grade plywood (not sure if there is plastic underneath) between the framed joists, fiberglass insulation then OSB in top the framed floor.  
So my main question is can I remove the subfloor, insulation and joists, and pour an new concrete slab using the outer joists as my form?

Answer
Hi Peter, Yes, this has been done before.  If the floor panels can be removed and the remaining rim joist is pressure treated wood then go for it.  Be sure to put at least a six mil. visqueen vapor barrier down underneath the slab to hopefully prevent the moisture intrussion from coming back.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com