When evaluating types of roofing systems for commercial buildings, the choice between a built up roof vs modified bitumen often comes down to understanding how each system performs under real-world conditions. Both bitumen roofing systems have protected commercial properties for decades, but they differ significantly in installation methods, maintenance requirements, and long-term value.
Understanding Built Up Roof Systems
Traditional BUR systems represent one of the oldest and most proven types of roofs for commercial applications. These multi-layer systems consist of alternating layers of bitumen and reinforcing ply sheets, creating a weather-resistant membrane that can withstand harsh weather conditions for decades.
How BUR Roofs Work
Built-up roofs typically include:
- A base sheet attached to the roof structure
- Multiple layers of asphalt alternated with reinforcing fabrics
- A surface layer of gravel or mineral cap sheets for UV protection
- Hot asphalt is applied between each layer for waterproofing
This construction method creates a thick, durable membrane that offers excellent waterproofing capabilities. The multiple layers provide redundancy, meaning if one layer develops an issue, the others continue protecting your commercial property.
BUR Performance Characteristics
Built-up roofing excels in several key areas. The thick membrane resists foot traffic better than many single-ply systems, making it ideal for commercial roofs with regular maintenance needs or rooftop equipment. The surface layer of gravel provides natural UV resistance and fire protection while creating a ballasted system that performs well in high winds.
However, installation requires specialized equipment and skilled labor. The hot asphalt application process demands careful temperature control and proper installation techniques. Labor costs tend to be higher due to the complexity and time required for the multi-layer application process.
Learn about single-ply roofing systems here → What Is Single Ply Roofing? Types & Benefits
Modified Bitumen Systems Explained
Mod bit represents an evolution of traditional built-up roof systems. These modified bitumen membranes incorporate polymers like atactic polypropylene or styrene-butadiene-styrene (SBS) to enhance performance characteristics beyond standard bitumen.
Installation Methods for Modified Bitumen
Modified bitumen roof installation offers more flexibility than BUR:
- Torch-applied: Uses heat to melt the membrane backing for adhesion
- Cold adhesives: Applied without heat for safer installation
- Self-adhering: Peel-and-stick application for specific applications
This variety in installation methods allows commercial roofing contractors to select the best approach based on building requirements, weather conditions, and safety considerations.
Modified Bitumen Advantages
The polymer modification improves several performance factors. Enhanced flexibility helps modified bitumen systems handle temperature changes and freeze-thaw cycles better than traditional bitumen. Many mod bit products incorporate reflective coatings or light-colored granules to improve energy efficiency by reducing heat absorption.
The ease of installation compared to BUR often results in lower labor costs and faster project completion. The thinner profile may also work better on roof structures with weight limitations.
Learn more about modified bitumen roofing here → What Is Modified Bitumen Roofing: Benefits, Costs, and Installation Process
Built Up Roof vs Modified Bitumen: Direct Comparison
Lifespan and Durability
BUR roofs typically deliver 20-30 years of service life with proper maintenance. The multiple layers provide exceptional resistance to water damage and punctures. Modified bitumen systems generally last 15-25 years, with modern formulations approaching BUR longevity while offering better flexibility.
Both systems require routine maintenance to achieve their full lifespan potential. Regular inspections help identify and address minor issues before they compromise the entire roofing system.
Weather Resistance Performance
Built-up roof systems handle extreme temperatures well due to their mass and multiple layers. The gravel surface reflects UV rays and insulates against hot weather. In heavy rain, the continuous waterproofing layers channel water effectively toward drainage points.
Modified bitumen membranes excel in cold-weather applications. Their enhanced flexibility prevents cracking during freeze-thaw cycles that can damage more rigid systems. The polymer modification also improves UV resistance compared to unmodified bitumen.
Cost Considerations Per Square Foot
Initial installation costs typically favor modified bitumen due to simpler installation requirements. BUR systems cost more upfront but may provide better long-term value for buildings expecting heavy foot traffic or extreme environmental exposure.
Business owners should evaluate the total cost of ownership, including maintenance requirements and expected service life, rather than focusing solely on initial square foot pricing.
Making the Right Choice for Your Commercial Property
The best decision between these commercial roofing systems depends on your specific needs. Consider these factors:
Choose BUR if you need:
- Maximum durability for high-traffic roofs
- Proven long-lasting protection
- Superior puncture resistance
- Excellent choice for industrial buildings
Choose Modified Bitumen if you prioritize:
- Faster installation timelines
- Enhanced flexibility for temperature extremes
- Lower initial investment
- Improved energy efficiency options
Both systems qualify as an excellent choice for low-slope roofs when installed by a professional roofing contractor. The right roofing system depends on your building’s structural capacity, local climate conditions, budget parameters, and long-term performance expectations.
Professional Installation Matters
Regardless of which flat roofing system you select, proper installation determines performance and longevity. Working with an experienced commercial roofing contractor ensures your roofing project meets manufacturer specifications and local building codes. Professional installation protects your investment and validates warranty coverage.
Great Lakes Commercial Roofing brings 99+ years of combined team experience to every roofing project. As a GAF Platinum Elite Commercial Contractor with multiple manufacturer certifications, we provide expert guidance on selecting the right system for your Pennsylvania or Iowa commercial property. Contact us today for a free roof inspection and detailed proposal comparing your options.
