2.0403.4 Pier and Skirting Foundations—Ground Moisture Barriers

Vapor Barriers
Desired Outcome: 
Durable, effective ground moisture barrier that provides ongoing access and minimizes ground vapor

If existing conditions of the ground and skirting mandates, a moisture barrier that covers the crawl space ground will be installed with allowances for structural supports (piers) and accessibility

Reduce ground moisture entering crawl space

Material specification

A ground moisture barrier with a rating of no more than 0.1 perm will be used

A ground moisture barrier will be used that meets tear and puncture resistance standard ASTM ASTM ASTM International, www.astm.org E1745

Homeowner will be advised that all plastic is biodegradable and will have a life span much shorter than the home (5 years), and it will need replacing to remain effective

Ensure crawl space is accessible for service and maintenance without damaging the integrity of the ground moisture barrier

Overlap seams

When seams exist, they will be overlapped a minimum of 12" using reverse or upslope lapping technique Reverse or upslope lapping technique Upper course laps under a lower course to keep the moisture under the barrier

Keep water under the liner

Reduce likelihood of damage at seams


Ground moisture barrier may be fastened to ground with durable fasteners

Prevent movement of the ground moisture barrier