Keep your hen house roof waterproof with an annual application of Thompsons Water Seal. Thompsons Water Seal has a unique formulation that uses hydrophobic technology to give invisible protection to your timber housing. 5-litre tin (it does what it says on the tin!) Unlike some water-proofers, it penetrates the surface to form a breathable membrane which will allow moisture to evaporate whilst protecting against water penetration and damage. It will not be destroyed by ultraviolet light and is long-lasting even under heavy moisture conditions.