Rick:

No, they aren't common here. Even when I see a vapor barrier, it's 6-mil polyethylene that's been seemingly applied with a scattergun. I always write up crawl spaces as in need of a vapor barrier and recommend the upgrade from 6-mil polyethylene to 20-mil EPDM or PVC pond liner with solvent-welded lap joints. Those are relatively permanent and can be traversed by repairmen and inspectors without damage.

The few builders here that still construct pier and beam foundations with crawl spaces are still living in the 50's technologically speaking. The last I saw was a new 6-million dollar box in Highland Park. The builder put down 6-mil polyethylene and then covered it with crushed rock (to properly perforate the plastic, I assume). In addition he added a high-end sump pump at the high end of the sloped crawl grade and humidistat-controlled fans that were installed backward (blowing into the crawl space - useless except for pressurizing the crawl and send the moisture through the wooden floors).

When I told him he had significant mold growth on the undercarriage, he scoffed. I got him an extra pair of coveralls from the van and invited him to crawl on that damned crushed stone to have a look. Served his knees just right.

Aaron