Built up roofing (BUR) is one of the oldest and most reliable commercial roofing systems, trusted for over 100 years. Its layered design continues to protect countless buildings across the U.S. If you’re evaluating roofing options, understanding BUR can help you make a smart, long-term investment.
A BUR system includes multiple layers of bitumen (asphalt) and reinforcing fabric, finished with a top layer like gravel or stone. This layered approach forms a seamless, waterproof barrier known for its strength and durability. The team at Pickle Roofing Solutions has extensive experience installing and maintaining these dependable systems.
In this comprehensive guide, we’ll explore everything you need to know about built up roofing, from its composition and installation process to its advantages, disadvantages, and ideal applications. By the end, you’ll have a clear understanding of whether a built up roof is the right choice for your commercial building needs.
Understand the Core Structure and Benefits of Built Up Roofing
A built up roof (BUR) is a multi-layer roofing system primarily used on low-slope or “flat” roofs. The system earns its name from the method of installation, literally “building up” multiple layers of materials to create a durable, waterproof membrane. The standard components include:
- Base sheet or vapor barrier
- Multiple layers of bitumen-saturated felt or fabric
- Hot or cold bitumen (asphalt or coal tar) between each layer
- A top layer or cap sheet
- Surfacing material (typically gravel, stone, or a reflective coating)
The number of layers (commonly referred to as “plies”) typically ranges from three to five, with more plies generally resulting in greater durability and longevity. A “four-ply” built up roof, for instance, contains four layers of felt or fabric embedded in bitumen, creating a robust barrier against water, UV radiation, and physical damage.
What sets built up roofing apart from single-ply roofing systems is this multi-layer construction approach. Rather than relying on a single membrane for protection, BUR systems distribute stress across multiple layers, enhancing overall resilience and reducing the likelihood of complete failure from a single puncture or tear.
Trace the Evolution of Built Up Roofing Through Time
Built up roofing has a remarkable history dating back to the late 1800s, making it one of the oldest continuous roofing systems still in use today. Early versions utilized coal tar pitch derived from coal gasification, along with organic felts made from rags.
These materials were readily available during America’s industrial revolution and provided effective waterproofing for the expanding number of commercial buildings with flat roofs. By the 1970s, asphalt largely replaced coal tar as the primary bitumen component due to environmental and health concerns associated with coal tar.
Similarly, organic felts evolved into fiberglass-based felts, offering improved fire resistance and dimensional stability. The 1980s saw the introduction of polymer-modified bitumen, enhancing the flexibility and weather resistance of BUR systems.
More recent innovations include:
- Cold-applied adhesives that eliminate the need for hot kettles, improving safety and reducing odors
- Reflective surfacing options that improve energy efficiency
- Environmentally friendly bitumen formulations with lower VOC emissions
- Integration with modern insulation systems for enhanced thermal performance
Today’s built up roofing systems offered by roofing specialists like Pickle Roofing Solutions represent the culmination of over a century of refinement and improvement, while maintaining the core principles that have made BUR a trusted option for generations.
Follow the Step-by-Step Process for a Quality BUR Installation
Understanding the installation process provides insight into the craftsmanship and attention to detail required for a quality built up roof. While specific techniques may vary based on project requirements and local building codes, the general process follows these steps:
1. Preparation and Planning
Before installation begins, thorough inspection and preparation of the roof deck are essential. This includes removing existing roofing materials (in reroof applications), repairing damaged decking, and ensuring proper drainage. The installation team will also verify that the structural support can handle the considerable weight of a BUR system, which typically ranges from 5-7 pounds per square foot.
2. Base Layer Application
Installation begins with a base sheet or vapor barrier directly applied to the roof deck or insulation board. This initial layer serves as the foundation for the entire system and may be mechanically fastened, self-adhered, or embedded in bitumen depending on the specific design requirements.
3. Building the Membrane
The defining phase of BUR installation involves alternating layers of bitumen and reinforcing fabrics. Hot bitumen (heated to approximately 400°F) is spread across the roof surface, followed immediately by rolls of roofing felt.
Each subsequent layer is fully adhered to the previous one, creating a continuous, monolithic membrane. Cold-applied adhesives may be used as an alternative to hot bitumen in certain applications.
4. Surfacing Application
The final step involves applying the protective top surface. For traditional BUR systems, this typically consists of a flood coat of bitumen followed by an aggregate layer of gravel or slag. Alternative surfacing options include mineral-surfaced cap sheets, reflective coatings, or specialized asphalt emulsions designed for UV protection.
Proper installation requires experienced professionals with specific equipment and expertise. The process is labor-intensive and can be time-consuming compared to single-ply alternatives like standing seam metal roof systems, but the resulting durability often justifies the additional effort and expense.
Discover the Lasting Benefits of Built Up Roofing Systems
Built up roofing has maintained its popularity in commercial applications for good reason. Here are the key benefits that continue to make BUR systems a preferred choice for many building owners and facility managers:
Exceptional Waterproofing
The multi-layer construction of built up roofing creates a seamless, redundant waterproofing system. Unlike single-ply membranes where one puncture can lead to leaks, BUR systems provide multiple barriers against water infiltration.
The alternating layers of bitumen and reinforcing fabrics create a monolithic membrane where water typically cannot penetrate beyond the surface layer, even if damage occurs.
Impressive Durability and Longevity
With proper installation and maintenance, built up roofs regularly achieve service lives of 20-30 years. Some high-quality installations have even lasted 40+ years in appropriate climates. This exceptional longevity stems from:
- Multiple redundant layers that distribute stress
- Self-healing properties of bitumen that can seal minor cracks
- Resistance to foot traffic and maintenance activities
- Superior weathering characteristics
- Excellent resistance to UV degradation
Strong Resistance to Extreme Weather
Built up roofing systems excel in challenging weather conditions. The substantial weight and solid construction make BUR highly resistant to wind uplift, while the multiple layers provide excellent insulation against temperature extremes. The gravel or aggregate surfacing adds further protection against hail impact and fire exposure, making BUR particularly well-suited for regions prone to severe weather events.
Low Maintenance Requirements
Once installed, built up roofs typically require minimal ongoing maintenance. The durable surface can withstand occasional foot traffic for equipment maintenance, and the self-healing properties of the bitumen layers can address minor issues before they develop into serious problems. Routine inspections twice yearly and after major storms are generally sufficient to maintain optimal performance.
Excellent Value Over Time
While the initial installation cost may be higher than some alternative systems, the extended lifespan and minimal maintenance requirements of built up roofing often result in lower life-cycle costs. When considering the total cost of ownership over decades, BUR frequently emerges as one of the most economical options for commercial buildings.
Weigh the Challenges Before Choosing Built Up Roofing
Despite its many advantages, built up roofing isn’t the ideal solution for every building or situation. Consider these potential drawbacks when evaluating whether BUR aligns with your specific needs:
Installation Challenges
BUR installation is more complex and labor-intensive than many modern roofing alternatives. The process requires specialized equipment, including kettles for heating bitumen, and skilled workers who understand proper application techniques.
Installation is also weather-dependent, as moisture trapped between layers can cause blistering and premature failure. These factors contribute to higher installation costs and potentially longer project timelines compared to single-ply options.
Weight Considerations
Built up roofing systems are significantly heavier than most alternatives, typically weighing between 5-7 pounds per square foot. This substantial weight requires adequate structural support, which may necessitate additional engineering considerations or structural reinforcement for some buildings. Older structures particularly may need assessment to determine if they can safely support a BUR system.
Odor and VOC Emissions
Traditional hot-applied BUR systems produce strong odors and volatile organic compound (VOC) emissions during installation. These issues can be particularly problematic for occupied buildings, healthcare facilities, or food processing plants where air quality concerns are paramount.
While cold-applied alternatives reduce these problems, they may not provide the same performance characteristics as hot-applied systems.
Environmental Considerations
The asphalt-based materials used in traditional BUR systems are petroleum products with associated environmental impacts. Additionally, at the end of their service life, BUR systems are difficult to recycle and typically end up in landfills. Modern alternatives like GAF roofing materials often offer more environmentally friendly options with similar performance characteristics.
Challenging Repair Process
While built up roofing systems are generally low-maintenance, when repairs are necessary, they can be more complex than with single-ply systems. Identifying the source of leaks can be difficult due to the multi-layer construction, and repairs often require specialized materials and techniques to maintain system integrity.
Identify Where Built Up Roofing Performs Best
Built up roofing performs exceptionally well in specific applications where its strengths align with project requirements. Understanding these ideal use cases can help determine whether BUR is appropriate for your building:
Commercial Low-Slope Buildings
BUR systems excel on large commercial buildings with low-slope or “flat” roofs (typically with slopes less than 2:12). The seamless, multi-layer construction provides superior protection for extensive roof areas where water might otherwise pond. Common applications include:
- Retail centers and shopping malls
- Warehouses and distribution facilities
- Manufacturing plants
- Office buildings
- Schools and educational facilities
High-Traffic Roof Areas
Areas that require regular maintenance access or support rooftop equipment benefit from the durable, puncture-resistant nature of built up roofing. The robust construction can withstand occasional foot traffic without damage, making it ideal for buildings with:
- Extensive HVAC equipment requiring regular servicing
- Solar panel installations
- Rooftop mechanical systems
- Maintenance access routes
Regions with Extreme Weather Conditions
The substantial weight and durability of BUR systems make them particularly well-suited for the following regions experiencing severe weather challenges:
- Hurricane-prone coastal areas benefit from BUR’s excellent wind uplift resistance
- Regions with heavy snowfall appreciate the system’s insulating properties and structural integrity
- Areas with extreme temperature fluctuations benefit from BUR’s thermal stability
- Locations prone to hailstorms gain protection from the aggregate surfacing
Projects Prioritizing Long-Term Value
When long-term performance takes precedence over initial cost considerations, built up roofing often emerges as a preferred solution. The extended service life and minimal maintenance requirements create excellent value over decades of use, making BUR particularly attractive for:
- Buildings intended for long-term ownership
- Facilities where roof replacement would cause significant operational disruption
- Properties where initial investment in quality materials is prioritized over short-term cost savings
- Institutional buildings with extended planning horizons
Explore Modern Upgrades Improving Built Up Roofing
While built up roofing maintains its traditional multi-layer approach, significant innovations have modernized the system to address contemporary building challenges:
Enhanced Energy Efficiency
Today’s BUR systems can incorporate reflective surfacing options that significantly improve energy efficiency. Instead of traditional dark gravel or aggregate finishes, modern options include:
- White mineral granules embedded in the cap sheet
- Aluminum coatings that reflect solar radiation
- Cool roof emulsions that reduce heat absorption
- Light-colored aggregate options that minimize thermal impact
These modifications can reduce cooling costs by 10-30% in hot climates while extending roof life by minimizing thermal stress and UV degradation.
Improved Installation Methods
Advancements in application technology have addressed many traditional BUR installation challenges:
- Cold-applied adhesives eliminate the need for hot kettles, improving safety and reducing odors
- Self-adhering base sheets minimize fastener penetrations and improve wind uplift resistance
- Specialized equipment allows for more precise bitumen application
- Factory-manufactured components ensure consistent quality
Hybrid Systems
Modern built up roofing increasingly incorporates elements from other roofing technologies to enhance performance. Common hybrid approaches include:
- BUR base layers topped with modified bitumen cap sheets for improved flexibility and strength
- Integration with spray polyurethane foam insulation for superior thermal performance
- Combination systems utilizing BUR in high-traffic areas and single-ply membranes elsewhere
- Modified bitumen sheets with factory-applied adhesive backing to eliminate field application of hot asphalt
Environmental Improvements
Responding to sustainability concerns, the built up roofing industry has developed more environmentally responsible alternatives:
- Low-VOC and low-odor bitumen formulations
- Recycled content in felt and reinforcement materials
- Vegetative roofing options that can be installed over BUR systems
- Extended service life that reduces replacement frequency and associated waste
Frequently Asked Questions
How long does a built up roof typically last?
A properly installed and maintained built up roof typically lasts between 20-30 years, with some high-quality installations extending to 40+ years under ideal conditions. Factors affecting longevity include climate exposure, maintenance practices, number of plies in the system, quality of materials used, and installation workmanship.
Regular inspections (twice yearly) and prompt repairs of minor issues significantly extend service life. Buildings in extreme climates with high UV exposure or frequent temperature fluctuations may experience shorter lifespans unless additional protective measures are incorporated.
What is the average cost of a built up roofing system?
Built up roofing typically costs between $5.50 and $9.00 per square foot for new installations, including materials and labor. Several factors influence this price range, including regional labor costs, number of plies (typically 3-5 layers), surfacing options (gravel being most economical, reflective coatings more expensive), insulation requirements, and roof accessibility.
While this represents a higher initial investment than some single-ply options, the extended lifespan often results in lower life-cycle costs when calculated over 20+ years of service. Additional costs may apply for tear-off of existing roofing or structural reinforcement if required.
How does built up roofing compare to single-ply membrane systems?
Built up roofing differs from single-ply systems like TPO, EPDM, or PVC in several key aspects. BUR offers superior puncture resistance and typically lasts 5-10 years longer than most single-ply options. However, single-ply systems install faster, weigh significantly less (1-2 pounds per square foot vs. 5-7 for BUR), and often provide better energy efficiency through reflective surfaces.
BUR excels in durability and redundant protection but requires more skilled labor for installation. Single-ply systems offer easier repairs and installation flexibility but may be more vulnerable to damage from a single puncture. The choice depends primarily on budget constraints, building structure, climate conditions, and planned ownership duration.
What maintenance does a built up roof require?
Maintenance for built up roofing is relatively minimal but essential for maximizing lifespan. Recommended maintenance includes semi-annual inspections (spring and fall), clearing debris from drains and scuppers, removing vegetation growth, checking flashings and penetrations for deterioration, and examining the surface for blistering or cracking.
After severe weather events, additional inspections should assess potential damage. Minor repairs typically involve reinforcing damaged areas with additional bitumen and fabric. More significant issues might require patch repairs using compatible materials. Professional roofing contractors should perform annual inspections to identify potential problems before they lead to leaks or structural damage.
Can a built up roof be installed in all climates?
Built up roofing can perform well in most climates with proper design considerations. In hot, sunny regions, reflective surfacing options help reduce thermal loading and extend roof life by minimizing UV degradation.
For cold climates, additional insulation layers and careful attention to vapor control prevent condensation issues. BUR performs exceptionally well in areas with high winds due to its substantial weight and monolithic construction. However, installation in very cold conditions (below 40°F) becomes challenging as bitumen may not adhere properly.
Similarly, extremely hot climates may require modified formulations to prevent softening during intense heat. Local building codes and climate-specific details should be incorporated into the design to optimize performance for regional conditions.
Explore Whether Built Up Roofing Fits Your Building’s Needs
Built up roofing represents a time-tested solution that continues to provide exceptional value for commercial buildings requiring durable, long-lasting protection. Its multi-layer construction creates redundant waterproofing that few other systems can match, while its substantial weight and monolithic structure provide outstanding resistance to extreme weather conditions.
Though the installation process demands skilled craftsmanship and the initial investment exceeds some alternatives, the extended service life and minimal maintenance requirements often result in superior long-term economics.
As with any roofing decision, evaluating whether built up roofing aligns with your building’s performance needs, budget, and long-term goals is essential. Consulting with a knowledgeable roofing professional can help you make an informed choice that protects your investment for decades.
About Pickle Roofing Solutions
Pickle Roofing Solutions brings over 15 years of expertise in commercial and residential roofing systems across Texas. Our team understands the demands of flat and low-slope roofing, offering specialized solutions like built up roofing for long-term durability and weather resistance.
We provide expert inspections, installations, repairs, and maintenance for built up systems, integrating modern techniques with time-tested practices. Whether you’re upgrading an existing structure or planning a new build, we deliver roofing solutions that stand up to harsh Texas conditions.
Connect with us today to schedule a consultation and find out if a built up roof is the right fit for your commercial building.