A Crawl Space Vapor Barrier is often referred to as a plastic material that resists diffusion of moisture from the dirt floor of the crawlspace.  The most often accepted definition is a plastic material covering the ground only. The code or standard thickness in most areas is 6 mil.  Many vapor barriers range in thickness from 4mil to 10 mil.  A vapor barrier is most often installed by builders as a means to fulfill their code requirements and pass inspections.  A vapor barrier is a starting point in reducing the moisture from the ground, but by no means is an ending point. Florida Under Home Solutions  includes a vapor barrier as step 4 in our 7 step process to drying a crawlspace. The next step would be to install our AmeriBrite Encapsulation System.

Florida Under Home Solutions has compiled a guide (Vapor Barrier Myths) on how to properly install a vapor barrier.

Do not be fooled by cheap imitation encapsulation systems!
The problem with the crawlspace industry is that there are so many contractors using a 6 or 10 mil vapor barrier material and calling it an encapsulation system.  They are not the same. The difference between a vapor barrier and encapsulation liner is the thickness, flexibility, multiple layers of plastic with cord reinforcement, and perm rating.  A 6, 8, 0r 10 mil polyethylene sheeting is meant to be used as a floor covering and not a permanent crawlspace encapsulation system.  It is not durable enough to stand the test of time. The plastic is easily pulled off the walls and is in need of constant repairs