The Patch Test Wondering Is my basement the source of condensation or mold elsewhere in the house? Preparing 1. Get some patches of clear plastic sheet about a yard square. 2. Get some sticky tape. Wider tape is easier to use. 3. Clear away enough stuff to attain access to a spot on the foundation wall and floor. Testing Stick the plastic flat onto the test surface. Seal the edges with tape. For dirt floors, use some of the dirt to hold the edges down tight to the rest of the dirt. Leave the patches alone for a day or two. (A watched foundation never effuses.) Analyzing Look through the plastic sheet and note any moisture accumulation. If you see a few stay droplets, your house may be subjected to just a few gallons of water. A dehumidifier could help to keep the area dry enough to avoid problems. If there are many droplets, your cellar may be evaporating 20 gallons a day into the house. This will cause trouble if you install insulation or do any air sealing. If the plastic is filling with water, it was silly to do this test. Your cellar is wet and you knew it all along. The roof and wall sheathing are probably rotten by now and you're just looking for someone to blame. If you find strange mushrooms growing under the plastic that seem to track your movements, you've got your own little shop of horrors. Back | Next