Basic Vapor Barrier Installation Instructions
Step 1: Preparation
Correct any drainage issues. Install a sump system if needed. Make sure downspouts are directed away from the home and there is a proper grade. Repair large cracks or damaged walls. Clean up low hanging ductwork, pipes, wiring and insulation. Clean walls with soap and water in preparation for application of fabrication tape. Walls should be free of any debris and dry before installing fab tape. Remove any debris and sharp objects. Rake the floor as level as possible. Install foundation vent covers and dehumidify the space if needed. If you have combustion appliances in your crawl space such as a furnace or water heater, you should consult your HVAC professional prior to installing a crawl space vapor barrier system. Always install a carbon monoxide detector in areas with combustion appliances.
Step 2: Install the Wall Curtain
Apply fabrication tape at least 3" below the top of the crawl space walls (snapping a chalk line can help you keep an even distance from the top of the wall). Apply fab tape on piers or support walls at least 18" above floor. Install vapor barrier directly to fab tape and trim around any obstructions or openings. Pipe boots will be installed later for pipes up to 8" diameter. Be sure to leave a gap at least 3" from the top of the wall to allow for termite inspection. Pipe and other wall penetrations should be cut and patched using fab tape. Seam tape can be added as desired for cosmetics and patching.
Now is a good time to install mechanical fasteners. Using a ¼" masonry bit, drill a hole through the vapor barrier at the center of the fab tape and install an expansion fastener every 3 feet. Installing these now will avoid getting concrete dust on your vapor barrier floor as well as give you extra strength should you pull on the vapor barrier while covering the floor area. Wipe dust from wall curtain prior to installing floor liner.
Step 3: Cover the Floor Area
Install vapor barrier over the entire floor area allowing for a 12" overlap for the wall curtain and all floor seams. Install vapor barrier on piers or support walls at least 18" above floor. Trim around any obstructions or openings and patch with fab tape and seam tape if desired. Pipe boots can be installed on top of the barrier for pipes up to 8" diameter. Remove debris and save tape and extra materials for repairs.