Modified Bitumen Roofing
From Roofs Wiki
Jump to navigationJump to search
Modified Bitumen Roofing
Modified Bitumen Roofing is a multi-layered, asphalt-based roofing system designed for use on Flat Roofs and low-slope buildings. It combines traditional Built-Up Roofing technology with modern polymer technology, making it one of the most durable and reliable systems for both Commercial Roofing and certain Residential Roofing applications.
Modified bitumen membranes are reinforced with modifiers like SBS (styrene-butadiene-styrene) or APP (atactic polypropylene) to improve flexibility, weather resistance, and longevity.
Key Features
- Multi-ply membrane system for enhanced waterproofing
- Resists foot traffic, UV damage, and harsh weather
- Can be applied with various methods: torch, cold adhesive, or self-adhered
- Suitable for buildings requiring a strong, long-lasting low-slope solution
Types of Modified Bitumen
SBS (Styrene-Butadiene-Styrene)
- Rubber-modified asphalt offering superior flexibility and cold-weather performance
- Typically installed with cold adhesives, hot asphalt, or torch-down methods
- Excellent elongation and crack resistance
APP (Atactic Polypropylene)
- Plastic-modified asphalt offering better heat resistance
- Usually torch-applied
- More rigid, ideal for warmer climates and UV exposure
Installation Methods
- Torch-Applied: Membrane is heated with a torch to bond with the substrate
- Cold-Adhered: Adhesives are used instead of open flame—ideal for sensitive buildings
- Hot-Mopped: Hot asphalt used to secure layers, similar to Built-Up Roofing
- Self-Adhered: Membranes with peel-and-stick backing for flame-free, low-odor installation
Advantages of Modified Bitumen
- Durability: Typically lasts 20–30 years with proper Roof Inspection and Maintenance
- Weather Resistance: Performs well in both hot and cold climates
- Versatility: Available in smooth or granule-surfaced membranes
- Repairability: Damaged sections can be patched easily
- Energy Options: Available with reflective cap sheets for Cool Roofs and Energy Efficiency
Ideal Applications
- Warehouses, retail centers, office buildings, and schools
- Structures requiring robust waterproofing and impact resistance
- Facilities needing reinforcement for rooftop traffic or equipment
Comparison with Other Systems
vs TPO Roofing
- TPO is a single-ply membrane, while modified bitumen is multi-ply
- TPO offers greater reflectivity, but modified bitumen provides better puncture resistance
vs EPDM Roofing
- EPDM is rubber-based and typically ballasted or adhered; modified bitumen is more durable under mechanical stress
vs Built-Up Roofing
- Modified bitumen is factory-made for consistency; BUR is built layer-by-layer on-site
- MB is typically lighter and quicker to install
Environmental Considerations
- May include recycled content
- Granule-surfaced options reduce heat absorption and qualify as Cool Roofs
- Cold-applied and self-adhered versions minimize fumes and on-site emissions
- May contribute to LEED Certification points depending on material and insulation
Maintenance Tips
- Schedule routine inspections, especially after extreme weather
- Seal flashings and penetrations as needed
- Check for ponding water, granule loss, or seam splits
