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How Important is Roofing Felt?

When it comes to roofing felt (A.K.A. tar paper, or underlayment), there is a lot of confusion and misinformation out there.  So we wanted to take this opportunity to provide you with the facts, not the sales pitch.

Roof Felt Underlayment Tar Paper

The Origins of Roofing Felt

Roofing felt has been around for over a hundred years. It was originally designed as a means to temporarily waterproof a roof after the shingles were removed.  Back before roofing contractors were so prevalent, many homeowners were forced to perform this backbreaking work themselves.  Roofing felt allowed more flexibility in the re-roofing process, making it possible for a small group of friends or family to remove the roof one weekend, install Roofing Felt (keeping the home dry during the week) and then install new shingles the next weekend.

It wasn’t until shingle manufacturers started producing their own brands of Roofing Felt, and looking for ways to improve their sales, that it was marketed as an “essential component” to their system. Since then, manufacturers have made improvements to the basic materials used, increasing the benefits of using felt.

What are the benefits of Roofing Felt?

  • Temporarily dries in a roof
  • Reduces likelihood of workers slipping, creating a safer work environment
  • May increase the fire rating of the roof system
  • Moisture barrier between wood decking and shingles

No one argues the benefits of felt, but sometimes overreaching salespeople make claims that simply do not hold water in an attempt to convince a client to spend more money on a “felt upgrade”.  It is important to realize that once the shingles are properly installed, thousands of nails penetrate the Roofing Felt, essentially ruining it – no matter how thick it may be. If a leak develops after the shingles are installed, the felt will not serve as a long term means of preventing it from entering the attic.

Yet, most contractors install it and most building codes require it for the reasons stated above. When used and marketed as the product was intended, installing roofing felt makes sense.

Why Use a Thicker Felt?

Although standard #15 felt is the most common temporary dry-in product, there are occasions that justify a thicker felt, such as #30.  The most frequent is a result of a steep pitch; the thicker felt resists tearing, making conditions safer for the installers.  However, thicker felt does not increase water resistance.

Felt is a temporary dry-in product and not designed to resist continued water exposure.  It creates a safer surface for workers to walk on.

These are benefits for the Contractor.

Warranties

A thorough search of today’s top manufacturers for information on their felt warranties can result in frustration.  It quickly becomes evident that although they are heavily pushing their felt product as an “essential part” of their roof system, they provide little to no information on their actual felt warranty.  Some go so far as to state “individual components take on the warranty of the shingles installed on the field of the roof.” The real means of waterproofing are the shingles themselves.

Although some counties and regional building codes have added certain felt requirements, most of the manufacturers themselves give no specific warranty coverage on their felt products.

Waterproofing Membranes (Ice & Water Shield)

In Georgia where “dead valleys” and slopes of 3/12 and less are common, specific waterproofing membranes may be required.  This product is not felt.  It is specifically designed to seal around the penetrating fasteners and act as a last defense against water penetration. Ice & Water Shield was developed primarily for Northern climates that suffer from Ice Damming but also to help minimize wind driven rain on low sloped roofing. In Southern, warmer climates it is often used as an alternative to metal as a valley liner.

Sparrow Exteriors

Sparrow Exteriors understands that not all roofs are identical and that each requires a customized installation.  We believe in providing you with the ideal roofing system for you and your home and/or business. If you have questions regarding felt or other forms of underlayment, please feel free to call us for more information.

 

Sparrow Exteriors specializes in roof replacement, roof repair, gutter installation, attic insulation, painting and siding; servicing the Greater Atlanta area and is proud to be a Georgia company. Whether you’re considering a home improvement, or you believe your home may have suffered hail and wind damage, call us for a Free, No Obligation Inspection!

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5 Comments

  1. Chandler McEwan July 30, 2013

    Question:
    I live in Kentucky and I am getting ready to install a new roof on my 19 year old house. I am concerned that the original roofer did not use felt paper. It’s a 3 tab shingle roof. Is there a simple way that I can tell?

    I haven’t had any real problems with leaks and from inside the attic there doesn’t appear to be damage but am I likely to find problems when the roof is removed?

    reply
    • Sparrow July 31, 2013

      Thanks for the question, Kentucky!

      To determine if roofing felt is present, go to where the roof overhangs the fascia. Typically you will see gutters, or drip edge along this horizontal edge of the roof. Carefully lift the shingles and you should be able to see the wooden decking, the felt, a starter course of asphalt shingles and the field shingles themselves.

      Worth mentioning here is that felt is not required by every State, city or county building code and even if roofing felt is now required in your area, 19 years ago it may not have been. Other factors such as the roof’s pitch (or steepness) also play a role as to what underlayment to use (tar paper, felt, modified bitumen, ice & water shield, etc). Felt is a temporary dry in product that will be ruined by the installation of the shingles with thousands of nail holes. It provides a slight increase in the fire rating and a safer surface to walk on for the installers.

      As to rotten decking being identifiable from the attic, an attic inspection can help but rotten decking is not always visible from inside. Given your roof is 19 years old, it is not unlikely to find bad wood around the roof penetrations. Also if the previous installer used face mounted toe-boards – meaning they nailed 2′x4′s into the shingles to walk on, rotten decking may exist around where they nailed these temporary boards in. We recommend that you be home during the removal of the old roof and verify the roof deck’s condition, or have your contractor ensure that they will provide you with either photos of any rotten decking, or set it aside so that you can see it.

      Despite the possible lack of roofing felt, we see no cause for alarm. However, we recommend consulting with a reputable contractor in your area for specific advice, or move to Atlanta and…

      reply
  2. Craig Anderson September 10, 2013

    Good article everyone should read. I like the statement ” It is important to realize that once the shingles are properly installed, thousands of nails penetrate the Roofing Felt, essentially ruining it – no matter how thick it may be.” Not every roofer would be this honest. I appreciate it and agree.

    reply
  3. John Bullington May 20, 2014

    The best article i have read on the roof felt question. I have tried in vein to tell this to our county inspector & county commissioners before they passed a rule to require it on reroofs.THE INSPECTOR said it was in the IBC but i did not find it under reroofing.I have reroofed a lot of homes which never had felt & never leaked. Like you said the average home will get about 4,000 to 6,000 nail holes in the felt. There goes your vapor barrier & water proofing stories. It was designed as a drying in tool only.

    reply
    • Sparrow May 29, 2014

      Thanks for the comment and compliment, John!

      Part of the issue is that in many instances the IBC, IRC and other building codes default to the manufacturer’s installation recommendations/requirements. This presents a problem as the manufacturers clearly benefit by promoting the sale of their other miscellaneous components, such as felt. They are hardly an impartial authority in the matter. Nevertheless, we believe there are legitimate benefits to using felt underlayments but often the hype and sales pitch is terribly misleading, thus the need for this article.

      Per the International Building Code (IBC):

      1507.2.3 Underlayment. Unless otherwise noted, required underlayment shall conform to ASTM D 226, Type I, ASTM D 4869, Type I, or ASTM D 6757.

      1507.2.4 Self-adhering polymer modified bitumen sheet. Self-adhering polymer modified bitumen sheet shall comply with ASTM D 1970.

      reply

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