One Chem Paving Sealant and Proofer is a water based formula suitable for use on porous and non-porous stone surfaces. Coverage 200-400ml per square metre. 2.5 litres covers up to 12.5 square metres. This Paving Sealant and Proofer 2.5 Litre Water Seal Protects against water, oil, and organic growth (e.g. green algae, mould and more).