2.0403.1 Vented Crawl Spaces—Ground Moisture Barrier

Vapor Barriers
Desired Outcome: 
Durable, effective ground moisture barrier provides long-lasting access and minimizes ground vapor
Material Integrity

Care will be taken to prevent punctures during installation

Protect ground moisture barrier from damage during other crawl space work


A ground moisture barrier that covers the exposed crawl space floor will be installed

Reduce ground moisture entering the 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 the likelihood of damage at seams


When ground moisture barrier is installed on sloping ground, may be exposed to wind, or accessed for routine maintenance or storage it will be fastened to ground with durable fasteners or ballast(s)

Prevent movement of the ground moisture barrier