Roofing Underlayments Defined

What is a roofing underlayment? Why does my house need a roofing underlayment? What is roof deck protection? Why do I need roof deck protection? What is roofing felt?

These are all common questions that we receive on all of our projects, so I would like to elaborate on roofing underlayments and roof deck protection.

First of all, if you are familiar with your roof and it’s make up at all, you have probably heard of roofing felt. Felt and it’s predecessor, tar-paper have been around for quite some time. Felt has been used for over 100 years and tar-paper before that. Felt is used in between your roof’s deck and the finishing product  (shingles). It is an important part of your roof system and if you are told it is not needed on your Asphalt Shingled roof, be very careful.

Roofing felt offers protection in a few different ways and improves the overall look of your roof. Many underlayments offer an improved rating when it comes to fire resistance, it is required for most shingle manufacturer’s warranties, it offers protection against wind driven rain, it offers protection against water if a shingle blows off of the roof, and it can protect shingles from chemicals that bleed out of the roof decking. Cosmetically it creates a more uniform surface to install asphalt shingles to; thereby creating an even looking finished roof (preventing buckling, bulging, etc.).

Now that you have a grasp of what roofing felts does, or attempts to do, I would like to describe some of the more specialized products we use for underlayment, how they further benefit you and why. If you follow us at all, you probably know at this point, we use GAF products for the vast majority of our projects. GAF offers a superior product with a superior warranty. We want to make sure our customers benefit in every possible way, on every project.


GAF Versashield

  • Offers a UL Class A Fire Rating
  • Protects against dangerous flame spread and penetration into the interior of the property
  • Provides temporary moisture resistance while the roofing system is being installed
  • Fiberglass reinforced; lays flatter for a better-looking roof


GAF RoofPro

  • Excellent Tear Protection vs the typical Organic Felt
  • Fiberglass reinforced; lays flatter for a better-looking roof


GAF Shingle-Mate

  • Part of GAF Smart Choice Weather Stopper Warranties
  • Lighter and Easier to Handle than #30 Felt
  • Fiberglass reinforced; lays flatter for a better-looking roof

GAF Tiger Paw

  • Helps remove nearly twice as much damaging moisture from your roof deck as the leading synthetic non-breathable underlayment
  • Non-asphaltic, polypropylene construction for long lasting performance (unlike conventional felts that can disintegrate over time)
  • Backed by a 20-year ltd. warranty against manufacturing defects
  • Synthetic, non-woven construction provides at least 600% (i.e. 7 times) greater tear strength than standard #30 felt
  • Up to 129% higher nail pull-through strength than #30 felt helps keep the product in place
  • Light-grey surface is cooler in hot weather than conventional black felts


GAF Deck-Armor

  • Helps prevent inside moisture from becoming trapped within your roofing system — and causing mold, mildew, and expensive structural damage
  • Exceptionally durable, non-asphaltic construction will not rot or become brittle (unlike conventional asphalt felts which can disintegrate over time)
  • Holds the approval of:
  • At least 600% (i.e., 7 times) greater tear strength than standard #30 felt!
  • Backed by a 25-year ltd. warranty against manufacturing defects


Please feel free to comment!


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  1. Pingback: Green Roofing for everyone | R-3 Roofing

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