IMPORTANT: *In most instances, Heavy Duty 38/40kg Roofing Felt will last at least twice as long as Standard 20kg Roofing Felt. However, you should be aware that all roofing felt can be damaged when exposed to extreme weather conditions such as strong winds, snow, hot sun, and torrential rain. It can also be damaged by children climbing, animals, birds, overhanging branches, and flying debris during storms, therefore despite this being the heaviest quality felt available, it still isn't covered under warranty.