J Quintero Roofing - When should I use 30lb felt? Most standard pitched roofs only need a 15lb. felt for proper underlayment. 30lb. is used for many specialty applications such as: low
GAF FeltBuster 48-in x 250-ft 1000-sq ft Synthetic Roof Underlayment in the Roofing Underlayment department at Lowes.com
Choosing Roofing Underlayment - Fine Homebuilding
Synthetic Underlayment: A Roofing Professional's Guide
Metal Roof Underlayment: What Are The Different Types?