What is a common material used as a moisture barrier in crawl spaces?

Polyethylene film is a common material used as a moisture barrier in crawl spaces because of its effectiveness in preventing moisture from the ground from seeping into the home. This thick plastic sheeting can be laid down over the soil in the crawl space to block moisture and reduce humidity levels, which are critical for protecting the structural integrity of buildings and preventing mold growth and wood rot.

Fiberglass insulation, while good for thermal resistance, does not serve as a moisture barrier; it can actually retain moisture if the crawl space is not properly ventilated. Steel sheeting is typically used for structural or protective purposes rather than as a moisture barrier, and although it can resist moisture, it does not provide the same protective properties as polyethylene film against ground moisture. Concrete slabs, while durable and resistant to moisture to some extent, are not specifically designed to function as moisture barriers; they can still allow moisture to migrate up from the ground unless additional barriers are applied. Thus, polyethylene film is recognized for its suitability and effectiveness in crawl space moisture control.