Water Stops (Temporary Protection) Water stops shall be applied at the end of each day’s work over exposed edges of insulation and membrane. Do NOT use coal tar for attachment of water stops to the structural deck where the possibility of pitch drippage may occur. Water stops must be removed cleanly from the insulation (top surface and vertical joint) and from the deck to ensure tight insulation joints and level insulation surfaces. Improperly removed water stops have been determined as a cause of roof splits, have prevented moisture vapor movement to vented edge details, and can result in pitch drippage.  Return to Application Considerations and Specifications