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Everlastic® MF-40 Flashing

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Everlastic® MF-40, A 40 mil self adhering membrane composed of 32 mils rubberized asphalt adhesive bonded to 8 mil polyethylene film.


Everlastic® MF-40 is a tough, self-adhering, self-healing composite membrane masonry flashing. When in place the membrane provides a barrier against water, air and vapor diffusion. Mechanical fastening through membrane will not destroy integrity.


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Everlastic® MF-40 Masonry Flashing complies with Volatile Organic Compound (VOC) regulations.


Flexibility and self-adhering nature of membrane allows for simple, positive and integral installation and field fabrication of splices, end dams, etc.   Everlastic� MF-40 Masonry Flashing provides a continuous bond to most substrates and is impervious to water and air penetration.  The membrane does not age harden, remains flexible over wide temperature ranges and is able to bridge small cracks.


Do not apply membrane in areas where it may be permanently exposed to the sunlight.  Membrane is not compatible with fresh coal tar or coal tar pitch and sealant products containing polysulfide polymers.  The use of thin-set tile systems with membrane is not recommended.  Provide sound, clean and dry substrate for surfaces to receive membrane. Install when air and surface temperatures are 25°F and above.


System: The masonry flashing membrane system consists of a membrane, adhesive and sealant. The membrane is a self-adhesive, cold-applied sheet composed of rubberized asphalt adhesive bonded to a polyethylene film. All end and side joints are sealed with a sealant.

Size: Everlastic® MF-40 is supplied in 18-inch wide rolls in 100 foot lengths and packaged 2 rolls per carton. Release paper protects the adhesive side until use.


General: Install Everlastic® MF-40 membrane in masonry at shelf angles, lintels, ledges and other obstructions to the downward flow of water in the wall.   Ensure masonry surfaces are smooth and free from projections that could puncture membrane. Seal penetrations in membrane with adhesive and sealant. Prime substrate with MF-40 Adhesive where existing conditions compromise membrane adhesion.

At cavity masonry walls: Extend membrane 1/2 inch back from exterior face of outer wythe of masonry through the outer wythe turned up a minimum 4 inches and tuck into bed joint of the inner wythe.

At masonry veneer walls: Extend membrane from exterior face of veneer through the veneer up face of sheathing at least 8 inches and behind barrier.

At lintels and shelf angles: Extend membrane a minimum of 4 inches into masonry at each end. At heads and sills extend membrane 4 inches at ends and turn up not less than 2 inches to form pan. Hold membrane back 1/2 inch from face. Use flashing drip to extend past face.

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Rubber, Neoprene, Foam, Gasket, Seal, Construction. To the best of our knowledge this published information is accurate, however, to determine suitability of material/product for a specific application is the user's responsibility.  Williams Products, Inc. shall not be liable for any loss or damage resulting from inappropriate usage.
Everlastic® is a registered trademark of Williams Products. All other products mentioned are registered trademarks or trademarks of their respective companies.
Contact Williams Products: Phone: 800-521-9594 or 248-643-6400 or Email:  Contact Information