Self-Adhesive Modified Bituminous Membrane Roof Systems: Considerations for Effective Low Slope Installation

Self-adhesive (SA) modified bituminous membranes provide an effective finished roof when properly
installed. These systems combine the long-term, proven performance of modified bitumen sheet
materials with installation advantages imparted by a self-adhesive bituminous layer.
Product Description, Manufacturing Process and Governing Standards
Self-adhesive modified bituminous membranes are comprised of asphalt, polymers, and tackifiers, and
may contain mineral stabilizers. The products may be reinforced with fiberglass, polyester, or a
combination of the two. Products designed for exposure to the elements are typically surfaced with
mineral granules, coatings, films, or other opaque surfacing. The self-adhesive layer is protected with a
release film or paper, which is removed during installation.
Labor saving application without the added complications of torching, mopping, or liquid adhesives is
one of the primary advantages of self-adhesive membranes. Because there are no kettles or torches
required, installation of self-adhesive membranes may be less disruptive to building occupants.
Many self–adhesive modified bituminous membranes are evaluated using test methods in ASTM
D5147, as are other modified bituminous sheet materials, and may meet the physical properties of
asphalt base sheets or modified bitumen sheet material standards such as ASTM D4601, ASTM D1970,
ASTM D6162, ASTM D6163, ASTM D6164, and CSA A123.23.
Product Storage Prior to Use
Self-adhesive modified bituminous membranes are generally packaged and stored in cardboard boxes or
they are protected with opaque wrapping. Unprotected self-adhesive products should not be stored in
direct sunlight since exposure to ultraviolet (UV) rays may affect the adhesive properties, especially on
the outer convolutions of the roll, or cause “dog-legging” of the roll. Storage for extended periods or
under extreme conditions can alter the adhesion properties of the self-adhesive bitumen or affect roll
alignment.
Installation
The following items should be considered when installing a self-adhesive membrane system.
 Always consult manufacturer’s application recommendations before specifying or installing a
particular product.
 At the time of installation, the air, product, and substrate temperatures should be at or above
the minimum application temperature recommended by the manufacturer. While the typical
minimum temperature range for application is 40-50°F, consult the specific manufacturer for
recommendations for material storage and handling during colder weather application. Selfadhesive products should only be applied to an acceptable substrate, as specified by the
product manufacturer. The substrate must be free of dust, dirt, oils, moisture or debris that
could interfere with proper adhesion.
 Manufacturers may require the substrate be primed prior to membrane application to aid
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adhesion of self- adhesive membranes. Primers are applied by brush, roller, or spray. Check
with the manufacturer to determine requirements for primer type, application rate, and drying
time. Solvent-based primers may damage the self-adhered membrane and roof system if the
solvent had not evaporated fully before the installation of the roof system.
 Unlike other installation methods for modified bitumen membranes, there is no liquid
bituminous layer to fill all the surface irregularities. Consequently, proper application is
essential, especially at all overlaps and T- joints. Applying pressure to the sheet with a heavy
roller is typically required. End laps on mineral-surfaced self-adhesive sheets may need to be
heat welded or sealed with compatible roofing mastics as specified by the manufacturer. If
using solvent-based mastic, following manufacturer recommended application rates and other
precautions to prevent solvent-induced damage to the membrane.
Where different grades of self-adhesive products and/or primers are available for cold weather
application refer to the manufacturer’s written instructions for guidance on proper product selection.
For more information, please consult the ARMA Modified Bitumen Design Guide for Building Owners.
The Design Guide addresses relevant aspects, issues and concerns of modified bituminous roofing
systems and their associated components, substrates, construction techniques and innovative uses.