How to Patch a Torn Basement Vapor Barrier
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 become 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 - Replacing the Vapor Barrier
Take the piece of vapor barrier which has been damaged and trim it 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 into the space you have just created in the vapor barrier. Raise the mastic into small peaks so that you will be able to press the plastic barrier down more firmly into it. Leave to dry overnight.
Step 3 - Make the Patch
Once the mastic is dry, place the patch onto the space you have cut and press down. Cover the edges with a layer of spray adhesive and leave it to dry in place.