Flex 80 Mil SS Base Sheet User Manual
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Flex Membrane International Corp. 2670 Leiscz’s Bridge Road, Suite 400, Leesport, PA 19533
Tel: (610) 916-9500 Fax: (610) 916-9501 www.FlexRoofingSystems.com
Page 2
LIMITATIONS
Non-resistant to oils and solvents. Refer to manufacturer for specific chemical resistance. Not designed for
permanent exposure. Install Flex SBS Granulated Cap Sheet Membrane over base sheet for permanent exposure.
STORAGE
Store rolls on end, on original pallets or elevated platform. Protect from weather or store in an enclosed area not
subject to heat over 120°F.
SURFACE PREPARATION
Refer to Flex's General Specifications for preparation and acceptable substrates.
APPLICATION
Flex SBS 80 Mil S/S Base Sheet must be mopped, nailed or cold adhered to substrate.
Begin application of the base sheet at the lowest edge or drain. Proceed up the slope from the lowest point. Position
and unroll base sheet to achieve correct overlap and alignment. Re-roll one end a minimum of 10' and adhere
membrane to substrate. Complete application of remainder of sheet.
Mopping Application: Roofing asphalt shall be Flex SEBS or ASTM D312 Type III on slopes up to 1:16 and
Type IV for slopes greater then 1:16. Use Flex SEBS or Type IV for all flashing.
Asphalt must be applied hot, so that it's mopping temperature is not below 400° F when measured
at the mop cart, to facilitate correct interply thickness, adhesion and uniformity. The roofing membrane must be
unrolled into the hot asphalt immediately. Mopping should not be more than 4’ ahead of unrolling.
Unroll into asphalt mopped at the rate of 20-30 lbs./100 ft², lapping 3” on sides and 6” on ends. The
Presence of a beed of asphalt should be observed flowing out of the seam. Mopping at ambient
Temperatures below 40º F requires special care and treatment. Refer to Flex’s General Specifications.
Cold Adhered Application: Apply Flex Bitumen Adhesive by notched squeegee to laps as well as the field of
the sheet at the rate of approximately 1.5 gal/100 ft².
A notched squeegee with notches ¼” long, 1/8” deep, spaced on 1” is ideal for smooth surfaces. For irregular
surfaces the notches should be ¼” deep. Best results occur above 50ºF. The adhesive thickens at colder
temperatures and proper coverage becomes difficult.
Roll out Flex 80 Mil S/S Base Sheet and allow to relax prior to application. Apply adhesive to substrate and allow 3
to 5 minutes open time prior to rolling in membrane. Installation without allowing open time could result in
prolonged softening of the membrane or blisters.
For flashings, apply Flex Flashing Cement adhesive by trowel in a 1/8” coat. Ensure full and uniform coverage.
Embed Flex 80 Mil S/S Base Sheet and apply pressure over the entire surface. Ensure a bead appears at laps.
Slopes 1:12 (1" in 12") or Greater: In addition to the above, apply membrane parallel to direction of slope
and blind nail or mechanically fasten membrane at end or head lap on 6" centers.
WARRANTY
Flex Membrane International warrants to the owner, that the SBS modified bitumen membrane, when installed by a
participating contractor subject to the conditions and limitations contained within the warranty, will remain
watertight for a period as outlined. All leaks or roof problems, on warranted roofs, must be reported to the
manufacturer in writing within a period of 30 days.