838 Coatings - MS Multi-Purpose Sealant, White, 750 ml Resealable Pouch

838 MS is a hybrid moisture-cure elastomer sealant formulated to encapsulate seams and fastener heads on metal roofing systems with minimal sag. Its 100% solids, solvent-free formulation is isocyanate-free and exhibits less moisture sensitivity than standard polyurethanes while maintaining high tensile strength and elongation.

The 750 ml resealable pouch format is well suited for sealing gutters, penetrations, and detailed repair areas where controlled dispensing and minimal waste are important. 838 MS conforms to the shape it is applied to, hangs vertically with minimal slumping, and adheres to a wide range of roofing substrates including metal, asphalt, EPDM, PVC, aged TPO, concrete, and brick. The material may be poured, extruded, or brushed depending on application needs.

Key features

• Hybrid moisture-cure elastomer sealant
• 100% solids, solvent-free, and isocyanate-free
• Designed to encapsulate roof seams, fasteners, and penetrations
• Minimal sag with strong vertical hang
• High tensile strength and elongation
• Adheres to metal, asphalt, EPDM, PVC, aged TPO, concrete, and brick
• Can be poured, extruded, or brushed
• Resealable pouch format helps reduce waste on smaller repairs

Brand: 838 Coatings
Product line: 838 MS (Multi-Purpose Sealant)
Product type: Hybrid moisture-cure elastomer sealant
Packaging type: Resealable pouch
Size: 750 ml
Total solids: 100% by volume
Application temperature: 42°F to 120°F (air and substrate)
Drying time: Tack-free approximately 1.5 hours (75°F, 50% RH)
VOC: < 1 g/L
Application method: Extrusion, pour, or brush
Use: Professional roofing and construction applications

Does it need perfect weather to apply?

No. This sealant can be applied in wet conditions and even underwater if needed. It cures faster than many comparable products, typically within 1–2 hours depending on conditions. As with any sealant, extreme conditions can affect working time, but it’s designed to perform when the job can’t wait on perfect weather.

Will this crack or get brittle over time?

No. Once cured, the sealant stays flexible, which helps it move with the roof and handle normal expansion and contraction.

Do I need fabric when applying this sealant?

No. Fabric is not required for standard applications. In most cases, the sealant can be applied directly to the surface and tooled as needed. Some installers may choose to reinforce certain details based on job conditions, but it’s not a requirement for use.