If you're building a chicken run, one of the decisions you'll need to make is whether to use roofing felt under the shingles. Roofing felt, also called tar paper, is a water-resistant material that is commonly installed under asphalt shingles or other roofing materials. But is it necessary or beneficial for a chicken run roof? Here is a comprehensive look at the pros and cons of using roofing felt under shingles on a chicken run to help you decide. What is Roofing Felt? Roofing felt is a paper or fiberglass mat that is coated with asphalt. The asphalt coating makes it water resistant to serve as a protective barrier between the roof deck and the shingles. There are different grades of roofing felt indicating the level of durability and weather resistance. Common grades used in residential roofing include: #15 felt - The lightest grade for use in drier climates #30 felt - The most commonly used grade for typical residential roofs #90 felt - A heavier grade for use...