Material needs will depend on the condition of the roof and how often you intend on recoating it. On tin roofs that are in relatively good condition, two coats applied at 100-150 square feet per gallon, per coat, will provide 5-10 or more years of protection. If your roof is leaking or has developed pinholes in the metal then additional material will be required. Our technical service staff will work with you to help calculate material requirements for your particular project based on information about your project that you provide; contact us.