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Asphalt Underlayment FAQ

Q: What is an 'asphalt felt' underlayment?

A: Asphalt-based underlayments are commonly called “felts” and traditionally have been used on roofs for over a century. The asphalt or bitumen component creates a water-resistant quality that helps provide a secondary layer of protection under the roof covering. This option may be the most affordable compared to synthetic underlayments.

Q: What are some of the benefits of asphalt underlayment as opposed to other materials?

A: Asphalt underlayment has been successfully used and recommended by roofing contractors for decades. The material offers an excellent all-round performance for a low price. Also, it is compatible with the most common roof covering, asphalt shingles. In many cases, asphalt underlayments are necessary with asphalt shingle roof systems for the following reasons:

  • To comply with building code
  • To maintain a fire rating for a roof assembly
  • To meet the manufacturer’s requirements for a material or system warranty
  • To cover minor deficiencies in a roof deck or substrate 

Q: What are the code requirements for the use of asphalt underlayment?

A: It will depend on the building code that is being enforced where the building is located. What might be compliant in one county could be non-compliant in the next.