Use of Asphalt Shingle Underlayment

There are three basic types of underlayment used under asphalt shingles: asphalt-saturated felt, self-adhering underlayment, and non-asphaltic synthetics (polymers).  The most common type of asphalt shingle underlayment is asphalt-saturated felt.  There are a number of important reasons for installing underlayment on wood decks before asphalt shingle application. Among them are the following:

·         Using the appropriate underlayment along with the proper roof deck material and asphalt shingles will ensure the required roof assembly fire-resistance classification, such as Class A, Class B and Class C, is met.  An asphalt shingle by itself is not classified for fire-resistance, although it is a part of the fire-resistance-classified roofing assembly. In many municipalities, a Class A, B, or C fire rating is required by code or ordinance for all roofing assemblies.

·         Asphalt shingle manufacturers direct the application of underlayment over wood roof decks.

·         Underlayment helps protect the roof deck until asphalt shingle application is completed.

·         Underlayment is water resistant. It provides secondary protection for the roof deck from wind-driven rain and other moisture penetrations.

·         Installing underlayment helps minimize “picture framing,” which is the visible outline of roof deck panels caused by irregularities in roof deck panel thickness or moisture migration at the roof deck joints that may telegraph through asphalt shingles.

·         Asphalt shingle underlayment helps protect the asphalt shingles from resins that may come from the wood roof deck.

·         The use of laboratory tested asphalt shingle underlayment products complying with ASTM D226, D4869 and/or D6757 is recommended and may be required by the asphalt shingle manufacturer and/or building codes. Local building codes may have different or additional requirements for types of underlayment.  The use of ASTM D1970 self-adhering underlayment may comply with manufacturer’s instructions and local building codes.

 

Follow printed instructions for application provided with the asphalt shingles and/or asphalt shingle underlayment to ensure optimum performance of the asphalt shingle underlayment and the asphalt shingle roof system.

 

 

DISCLAIMER OF LIABILITY: This document was prepared by the Asphalt Roofing Manufacturers Association and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual roofing material manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the roofing manufacturer concerned. THE USER IS RESPONSIBLE FOR ASSURING COMPLIANCE WITH ALL APPLICABLE LAWS AND REGULATIONS.

Nothing contained herein shall be interpreted as a warranty by ARMA, either express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose or non-infringement. IN NO EVENT SHALL ARMA BE LIABLE FOR ANY DAMAGES WHATSOEVER, including special, indirect, consequential or incidental damages or damages for loss of profits, revenue, use or data, whether claimed in contract, tort or otherwise. Where exclusion of implied warranties is not allowed, ARMA’s liability shall be limited to the minimum scope and period permitted by law.

 

 

Residential Roofing