505MS Karna Flex WB SILO 3 LITE

505MS Karna-Flex WB Sealant

505MS Karna-Flex WB Sealant

Available in: 1 gallon cans, 3.5 gallon buckets, 5 gallon pails and 30 oz. caulking tubes

505MS Karna-Flex WB is an acrylic elastomeric, water-borne mastic formulated for use on built-up asphalt roofing, modified bitumen membranes and properly prepared, single-ply membranes (TPO, PVC, Hypalon, and EPDM) and plywood roof substrates. Its ease of application, superior adhesion, elasticity and durability make 505MS Karna-Flex WB an ideal repair sealant.



1. White elastomeric sealant.
2. Easy application by brush or bulk loading caulking gun.
3. Excellent adhesion to many surfaces.
4. Sets up quick for coating over.
5. Low temperature flexibility—specially selected polymers and resins impart
superior low temperature properties to the coating.
6. Low VOC, water-based, no odor.
7. Resistant to mold and mildew growth.
8. UV stable, may be left exposed.


  • ASTM C-734


505MS Karna-Flex WB’s elastomeric properties make it an excellent sealant for making repairs to built-up asphalt roofs, modified bitumen membrane roofs, prepared metal, concrete, spray polyurethane foam and plywood roof system details. Ideal for sealing flashings, curbs and waterproofing metal roof seams, gutters, fasteners, pinholes in metal and skylights. Excellent for sealing flashings on asphalt BUR roofs and modified bitumen membrane roofs. Ideal for sealing around penetrations and roof top equipment. Use in place of flashing cement for repairs to all types of asphalt roofs prior to applying white coatings.

Product data sheet: Roofing

Product data sheet: Metal

Physical Properties

Weight per Gallon: 11.8 lbs
%NV by Weight: 70%
%NV by Volume: 65%
Color: White
VOC: 70 g/L
Tensile Strength: 40 psi.
Elongation: 500%
ASTM C-734 Low Temp Flex: Pass No Cracking
Recovery: 75% min.

Preparation & Application

All surfaces to be sealed must be dry, clean and free from rust, loose coating and caulk, oil, grease and other foreign matter. Remove silicone or other sealants before using.

APPLICATION:General Repairs
505MS Karna-Flex WB should be applied by stiff brush or bulk loading caulking gun, depending on the application. Apply sealer when temperatures are above  40ºF and rain is not forecasted within 24 hours. For sealing flashings and lap seams use fabric reinforcement between layers of 505MS Karna-Flex WB. Apply sealer in a 1/16” to 1/8” width then immediately embed KARNAK 5540 Resat-Mat polyester fabric into the wet coating. Smooth out fabric then apply another  layer of sealer. Some shrinkage may occur and require an additional application of 505MS Karna-Flex WB.

For metal roofing follow these application guidelines:
1. Horizontal Seams and Cracks 1/16” wide or larger.
• Using KARNAK 550 Patch-N-Go Fleece Tape, adhere tape to crack as directed per product application guidelines. Apply 505MS Karna-Flex WB at an average  thickness of 1/16” to completely cover the polyester face of the tape and feather out.
• Using KARNAK 5540 Resat-Mat, apply a 1/16” thick application of 505MS Karna-Flex WB then immediately embed one ply of 5540 Resat-Mat polyester fabric into the wet coating. Smooth out fabric then apply another layer of 505MS Karna-Flex WB.
2. Screws/Fasteners, Vertical Seams and Cracks less than 1/16”
• Over screws and fasteners apply a dollop of 505MS Karna-Flex WB to completely enclose the screw/fastener with either a 2” wide brush or bulk loading caulking gun.
• Over vertical seams and cracks less than 1/16” wide, back brush a minimum 2” wide application of 505MS Karna-Flex WB at an appropriate thickness of 1/16” to 1/8”.

Note: Allow to cure 24 hours before coating over, if desired. Not intended for use
in ponding areas.

Caution/Care of Tools

Do not apply when rain is imminent. Protect from freezing. Sealant must be dried before exposure to water. Do not take internally. If swallowed, do not induce vomiting. Call a physician immediately. KEEP OUT OF REACH OF CHILDREN. Keep container covered when not in use. Do not thin. Dispose of in an environmentally safe manner. Cover air intakes during application and while drying. Not for use on areas that pond water, roofs should have positive drainage.

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