Self-Adhesive Modified Bituminous Roofing Membranes

Modified bituminous roof membranes continue to be popular option for low-sloped roofs due to their proven performance. Historically these products have been torch-applied, mop-applied using hot asphalt (SBS only), or applied with solvent-based adhesives.

Manufacturers’application recommendations must be consulted before specifying or installing a particular product, but some general considerations related to the application of self-adhesive membranes include the following:
·Self-adhesive membranes are generally packaged and stored in cardboard boxes or 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. Extreme storage time and conditions can alter the tack properties of the SA bitumen blend. Consult the membrane manufacturer if the SA bitumen is not tacky to the touch.

·Roof must have adequate slope and drainage.

·When used over decks with attic spaces, ensure that the installation of the self-adhesive membrane does not prevent or interfere with the ventilation of the existing construction. Typically these materials form a vapor retarder, and if applied over warm attic spaces, adequate and thorough ventilation is needed to prevent condensation.

·The following information varies significantly by manufacturer. Individual suppliers should be consulted for specific recommendations.

·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.

·The substrate must be free of any dust, dirt, oils, moisture or debris that could interfere with proper adhesion. Often the roof surface must be primed prior to membrane application – check with the manufacturer regarding requirements for primer type, application rate, and drying time as primer technology for SA sheets continues to evolve.

·Self-adhesive membranes should only be applied to an acceptable substrate; consult the specific manufacturer for acceptable substrates.

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. End laps on the mineral-surfaced SA sheets may need to be heat welded or sealed with compatible roofing mastics as specified.