Liquid Systems Liquid systems can be applied to a variety of roof coverings and can give your roof or side cladding a new lease of life. If re-roofing an old roof is too expensive, consider the application of a liquid weatherproofing system, which will give the old covering an extended life-span. The new liquid applied coating can be guaranteed for typically 10-25 years. There are a number of products currently on the market and can be bitumen-based, acrylic-based or polyurethane.