Belzona 3121
MR7
A liquid-applied emergency roof repair material providing instant waterproofing of leaking roof areas.
A 2-part polymer composite for emergency roof repair providing instant waterproofing in all weather conditions.
- SeriesBelzona 3000 Series
- Approvals1
- Documents5
Overview of Belzona 3121
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
Applies and cures down to 0°C (32°F) and even during adverse weather conditions
Easy to mix and apply without specialist tools
Cures at room temperature without hot work
Allows trapped moisture to escape while providing long-term weatherproofing protection
Bonds strongly to virtually any rigid surface
Adapts to roof movements and building expansion due to outstanding elasticity
Applied by brush or spray for fast and efficient coverage
Application Areas
What this product handles, grouped by equipment area — each links to the full application.
Roof Problem Areas
4 applications- Roof waterproofing & leak repairRoof repair and weatherproofing applications requiring reliable performance in adverse weatherLearn more
- Joint, seam & upstand weatherproofingSealing of joints and seams to provide weatherproofing and waterproofingLearn more
- Roof flashing and roofingGutter linings, parapet copings, and metal flashing details take the worst of any roof's thermal and water load, with movement at every dissimilar-material joint working…Learn more
- Roof membranesBuilt-up roof systems and single-ply membranes lose integrity at penetrations, seams, and parapet flashings where UV cycling and thermal movement work the existing seal…Learn more
Technical Data
Base Component
- Appearance
- Thixotropic liquid
- Color
- Gray
- Density
- 1.61 - 1.63 g/cm³
- Viscosity
- 86 - 94 poise at 104°F (40°C)
Solidifier Component
- Appearance
- Clear liquid
- Color
- Yellow
- Density
- 0.97 - 1.01 g/cm³
- Viscosity
- 7.5 - 11.5 cp at 68°F (20°C)
Tensile & Elongation Properties (ASTM D412 Die C)
- Tensile Strength Reinforced
- 800 psi (5.5 MPa)
- Tensile Strength Unreinforced
- 1,140 psi (7.9 MPa)
- Elongation Reinforced
- 150%
- Elongation Unreinforced
- 400%
Tear Strength (ASTM D624 Die C)
- Reinforced
- 180 pli (3,229 kg/m)
- Unreinforced
- 140 pli (2,512 kg/m)
Hardness (ASTM D2240, 24 hr cure at 68°F)
- Shore A
- 35
Water Vapor & Weathering
- Water Vapor Permeability (ASTM D1653, reinforced)
- 17 g/m²/24 hrs
- Weathering (ISO 11341)
- Approximately two-thirds of original elongation maintained after 1,000 hours of accelerated weathering
Service Temperature Limits
- Application temperature
- Down to 32°F (0°C)
- Low temperature flexibility
- Maintains flexibility down to -8°F (-22°C), passing ASTM D522 mandrel test at minimum 3.2 mm diameter
- Cures in adverse weather conditions including rain
Mixing & Application
Certifications & Approvals
Product PDFs
Gallery
Videos
Frequently Asked Questions
What common problems cause roof leaks that Belzona 3121 (MR7) can fix?
Roof leaks often occur due to aging or damaged roofing materials, failed joints and seams, cracked flashing, or weather-related wear and tear. Issues like these allow water to penetrate the roof, leading to internal damage and urgent repair needs.
How does Belzona 3121 (MR7) address these roofing problems?
Belzona 3121 (MR7) is a liquid-applied, two-part polymer composite designed for emergency roof repair and weatherproofing. It bonds strongly to a wide range of roofing surfaces — including slate, tile, asphalt, felt, asbestos cement, and metal — even in adverse weather conditions. Its fast-curing, flexible system incorporates a reinforcement sheet, adapting to roof movements and complex contours, and provides instant waterproofing, even if applied during rain or on wet surfaces.
What are the key features that make Belzona 3121 (MR7) effective for urgent roof leak repairs?
- Can be applied and will cure in wet or cold weather, providing immediate water resistance
- Requires no primers or conditioners and is easily applied by brush
- Forms a seamless, flexible membrane that adapts to roof movement and resists further leaks
- Bonds to most common roofing materials, making it suitable for various emergency repairs such as sealing leaks, joints, seams, gutters, and cracks
These features make Belzona 3121 (MR7) an ideal solution for quickly and effectively addressing the root causes of roof leaks and preventing further water ingress.
Related Products
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