Belzona 3121 (MR7)

A liquid applied emergency roof repair material providing instant waterproofing of leaking roof areas.

Belzona 3121 (MR7)

A 2-part polymer composite designed to provide emergency roof repair and weatherproofing for leaking roof areas. Belzona 3121 (MR7) is liquid-applied and bonds strongly to all common roofing surfaces including slate roofs, tile roofs, asphalt, felt, asbestos cement sheet roofs and metal roofs, even during adverse weather conditions.

This fast curing, all climate flexible repair system incorporates a reinforcement sheet which ensures the coating will adapt to roof movements and follows complex roofing contours. This system is water resistant immediately after application and can cure even if fully immersed in water.

Key benefits:

  • Can be applied and will cure even during adverse weather conditions
  • Simple application method with no primers or conditioners required
  • Application and cure as low as 0°C (32°F)
  • No hot work involved
  • Microporous structure allows trapped moisture to escape whilst providing long-term weatherproofing protection
  • Excellent adhesion to a wide range of materials including felt, asphalt, lead, zinc, cooper, glass, concrete and brick
  • Adapts to roof movements with its outstanding elasticity
  • Can be easily applied by brush

Applications for Belzona 3121 (MR7) include:

  • Emergency repair of roof lights, gutters, splits in roofing felt, leaking joints and other roof areas
  • Sealing of joints and seams to provide weatherproofing and waterproofing
Key technical data:
Working life at 20°C (68°F) 2 hours
Cure time The system is water resistant immediately and can cure even if fully immersed in water
Tensile strength (ASTM D412 (Die C)) 800 psi (5.51 MPa) reinforced, 1,140 psi (7.86 MPa) unreinforced
Water vapour permeability (ASTM D1653) 17g/m²/24
Recommended coverage rate (per ltr) Practical coverage rate for a 2 coat system: 
1st coat 1.9 sq.m. (20 sq.ft.) per litre on asphalt, smooth felt, bitumen and metals

2nd coat 2.0 sq.m. (21 sq.ft.) per litre on asphalt, smooth felt, bitumen and metals
Bonds to Felt, asphalt, lead, zinc, cooper, glass, concrete, brick and many more
Typical applications Emergency roof repair including leak sealing, waterproofing and weatherproofing 
Unit size 0.75 litres, 3 litres. Pack sizes may vary locally
Availability* Global

* All products are subject to regional restrictions. Check with your local Distributor for more information


More information:

For more information about Belzona 3121 (MR7) contact us or find your local distributor.

You can apply to join Belzona Connect to access additional information including SDS and instructions for use.

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