HOW THICK IS 40 LB ROOFING FELT?

Forty-pound roofing felt, also known as #40 felt, typically has a thickness of about 0.30 to 0.35 inches. This thickness can vary slightly based on the manufacturer and specific product, but it is generally designed to provide a durable underlayment for roofing applications. It is heavier and thicker than the more common 15-pound and 30-pound felt options.