moisture barrier ???

BOZONE · 03-12-2010, 02:48 PM

I live in Florida and have a old Jim Walter home (off ground - on blocks) not good air flow underneath and no moisture barrier - had remodeling done about 6yrs ago and they put plywood over existing hardwood and then tile directly on plywood - now floor has rotted out totally along with needing to replace some of the joists - want to do it right this time around

Bob Mariani · 03-12-2010, 07:05 PM

you should have a sealed skirt around the building. (no air flow) then cover the ground with 6 mil poly and attach to the underside of the building perimeter. Never install tile on wood. Install the tile on Ditra only after you are assured no moisture migration is still persistent into the subfloor.

JazMan · 03-12-2010, 09:35 PM

I don't think I agree with Bob on his sealed skirt idea. Generally you want some kind on membrane over the well draining soil, a vapor barrier/insulation between the joists, or foam, and plenty of cross ventilation.

The specifics are determined by location and soil type however. What should be done in your case may be different from a home 100 miles away, and certainly different from what I should do here in the north half of the country.

You should consult someone that would be considered an expert, (not someone at the big box stores). A reputable insulation company or maybe start with your town's building department.

Jaz

Bob Mariani · 03-13-2010, 08:41 AM

code in the past has required cross scintillated crawlspaces. Now after 10 years of building science we find this is not correct. For energy and building performance tax credits you need work done by certified contractors specializing in this work. These regulations required us sealing this area and keeping moisture from entering into the building from below.