Foster® Weatherite™ Mastic 46-50

• WEATHERITE™ MASTIC has excellent brush, trowel, and spray properties, is non-flammable when wet, and has a mild odor during application.
• WEATHERITE™ MASTIC forms a tough, fire-resistive dry film that is extremely flexible and provides a smooth, attractive finish on both indoor and outdoor applications.
• It has excellent adhesion to most foil facings. It may be used over a wide variety of thermal insulations including polystyrene and rigid polyurethane board stock insulations.  
• WEATHERITE™ MASTIC 46-50 meets the requirements of:
  • MAS Certified Green®
  • California Dept. of Public Health Standard Method v1.2
  • VOC Emissions and Content requirements to contribute to LEED v4 EQ Credit: Low Emitting Materials – Paints and Coatings
  • Collaborative for High Performance Schools EQ 7.1

Material Preparation

• Do Not Thin.
• WEATHERITE™ Mastic will appear to be thick, but this is a “false” consistency which breaks down readily on application.
• Stirring is not necessary.
• Apply only to clean, dry, oil-free surfaces.
• Keep container closed when not in use.

Application – Hot and Dual Temperature Surface 

• Follow flashing recommendations when installed outdoors.
  • MAST-A-FAB® Reinforcement : Apply a tack coat of Foster® WEATHERITE™ Mastic at a thickness of 1/32 inch (0.8 mm). This is equivalent to 2 gallons per 100 square feet (0.8 l/m2 ). Embed Foster® MAST-A-FAB® white membrane into wet tack coat. Smooth membrane to avoid wrinkles and overlap all seams at least 2 inches (51 mm). Apply a finish coat of WEATHERITETM Mastic at a minimum thickness of 1/16 inch (1.6 mm) this is equivalent to 4 gallons per 100 square feet (1.6 l/m2 ). This finish coat shall be applied no later than 1/2 hour after the tack coat and shall completely cover the membrane. This application shall provide a minimum dry film thickness of 58 mils (1.5 mm).
  • Heavy Duty Applications – Up to 50% Greater Tensile Strength : Apply as above, substituting CHIL-GLAS® #5 as the reinforcing membrane. Note that the membrane weave pattern will show through the dried mastic. For best results, prime hygroscopic alkaline cements with Foster 32-22 Protektor® Sealant. Both the cement and the primer must be completely dry before the WEATHERITE™ Mastic is applied.
• Trowel : Use a clean steel trowel. Apply each coat in full thickness before initial set. Avoid excessive troweling.
• Brush :  Use a good brush (suitable for water-based paints), making strokes as long as possible over the surface. Apply with full brush and spread out evenly. Do not overwork. Multiple coats will be needed to achieve the minimum dry film thickness.
• Spray :  Foster® WEATHERITE™ Mastic may be airless spray applied. For spray equipment information, please consult Airless Spray Recommendations or contact your spray equipment supplier. Average viscosity range: 100,000-130,000 cps. Corrosion resistant pumps and fittings are suggested.
• Clean Up : Use fresh water to clean brushes and equipment before product dries. Dry product may be removed with hot soapy water or strong solvents such as chlorinated solvent (non-flammable) or xylol (flammable).

• Store and apply between 4°C and 38°C, protect from freezing until dry.
• To resist rain washoff, allow at least 24 hours drying time above 16°C with a relative humidity of 50%.
• Higher humidity and/or lower temperatures will retard drying.
• Always test foil and paper facings for acceptable adhesion before using.
• Outdoor horizontal surfaces must always drain completely.
• A pitch of at least 1/2 inch per foot (4 cm/m) is required.
• Always select WEATHERITE™ MASTIC in the white color for use over polystyrene on outdoor installations.