If you have fitted a basement vapor barrier, you must check it regularly for tears and holes. Any damage to the surface of the vapor barrier will lead to moisture breaching the surface. As a result, your insulation becomes wet, moldy, or rotted. The best way to prevent water damage to your insulation is to repair tears in your basement vapor barrier before they allow moisture to harm your insulation.
Step 1 - Begin Vapor Barrier Repair
Take the piece of vapor barrier which has been damaged and trim away the damaged edges using the razor knife. Cut a piece of vapor barrier material slightly larger than the hole you have just cut. Trim it to fit and set it aside.
Step 2 - Add a Layer of Mastic
Place some mastic onto a trowel and smear it around the opening you have just created in the vapor barrier. Raise the mastic into small peaks so you will be able to press the plastic barrier down more firmly into it. You will have about 10 minutes before it starts to set to place the patch onto it.
Step 3 - Make the Patch
Once in place, the mastic will dry within 24 hours.