Built-Up Roofing (BUR) is a classic and proven roofing system widely used in commercial and residential buildings with flat or low-slope roofs. Known for its durability and multi-layer protection, BUR roofing involves multiple layers of bitumen and reinforcing fabrics. This article explores the essential components, installation techniques, advantages, and maintenance of BUR roofing to help property owners understand why it remains a trusted roofing solution.
| Aspect | Description |
|---|---|
| Definition | Multiple layers of bitumen and reinforcing fabrics creating a durable roof membrane |
| Common Use | Flat and low-slope roofs on commercial and residential buildings |
| Main Components | Asphalt/coal tar, fiberglass or organic felts, gravel or mineral surface |
| Installation Method | Layering of hot or cold applied bitumen and felts, topped with protective surfacing |
| Key Benefits | Durability, UV resistance, excellent waterproofing, and fire resistance |
| Maintenance | Periodic inspection, cleaning, and repair of surfacing |
What Does BUR Roofing Mean?
Built-Up Roofing, abbreviated as BUR, is a traditional roofing method involving the application of alternating layers of bitumen (asphalt or coal tar) and reinforcing fabrics like fiberglass or organic felt. These layers create a robust, waterproof membrane designed to withstand the harshest weather conditions and traffic loads. The top layer typically includes gravel or mineral granules which protect the roof from ultraviolet rays and mechanical damage.
The History and Evolution of BUR Roofing
BUR has been in use for over a century, originating in the early 1900s to address the challenges of flat roofing. Early BUR systems primarily used coal tar and organic felts, evolving to incorporate asphalt and fiberglass felts for enhanced longevity and fire resistance. Despite the rise of newer roofing technologies, BUR remains a popular choice due to its proven performance and cost-effectiveness.
Key Components of a BUR Roof
| Component | Description | Purpose |
|---|---|---|
| Bitumen | Asphalt or coal tar used as adhesive and waterproofing layer | Bonds felts, provides waterproofing and resilience |
| Reinforcing Fabrics | Fiberglass or organic felt mats | Reinforce the roof membrane and add tensile strength |
| Surfacing Layer | Gravel, mineral granules, or reflective coating | Protect against UV damage, mechanical abrasion, and weathering |
How Is BUR Roofing Installed?
The installation process for BUR roofing is methodical and involves several steps to ensure a seamless, watertight membrane:
- Deck Preparation: The roof deck must be clean, dry, and structurally sound.
- Base Sheet Installation: A base sheet is often installed to create a solid foundation.
- Layering of Bitumen and Felts: Multiple layers of hot or cold applied bitumen are alternated with reinforcing felts. Typically 3 to 5 membrane plies are used.
- Surfacing: The top layer consists of gravel, mineral granules, or a reflective coating to shield the membrane.
The layering creates a thick, durable membrane capable of resisting water penetration, UV rays, and foot traffic damage.
Advantages of Choosing BUR Roofing
BUR systems offer several benefits that make them a preferred roofing solution for flat roofs in the U.S.
- Superior Waterproofing: Multiple bitumen layers create an almost impervious barrier to water.
- Long Lifespan: Typically lasts 20-30 years with proper maintenance.
- Fire Resistance: Especially with coal tar bitumen, BUR roofs have excellent fire-resistant properties.
- UV Protection: Gravel or mineral surfacing shields the membrane from sun damage, preventing premature aging.
- Low Maintenance: Requires only periodic inspections and minor repairs.
- Cost-Effective Installation: BUR tends to be more economical over its service life compared to some modern systems.
Common Uses of BUR Roofing in the United States
BUR roofing is widely applied in commercial buildings like offices, warehouses, schools, and retail establishments because of its strength and longevity. It is also suitable for residential properties with flat or low-slope roofs seeking durable waterproofing solutions. BUR is often favored where roof traffic is expected or where environmental exposure is especially harsh.
Maintenance and Longevity Tips for BUR Roofs
To maximize the lifespan of a BUR roof, consistent maintenance practices are recommended:
- Regular Inspections: At least twice annually and after severe weather events.
- Cleaning: Remove debris, leaves, and dirt to prevent water pooling and surface damage.
- Surfacing Repair: Replace lost gravel or mineral granules to protect bitumen from UV rays.
- Patching Membrane Damage: Address blisters, cracks, or punctures promptly to avoid leaks.
- Professional Assessments: Use certified roofing contractors for assessments and repairs.
Proper upkeep can extend a BUR roof’s life by several years, preserving its waterproof integrity and preventing costly replacements.
Comparing BUR Roofing With Other Flat Roofing Options
When considering roofing systems for flat roofs, BUR is often compared to other popular choices:
| Roof Type | Typical Longevity | Cost | Key Advantage | Notable Disadvantage |
|---|---|---|---|---|
| BUR | 20-30 years | Moderate | Durable, proven waterproofing | Heavy weight, labor intensive installation |
| Modified Bitumen | 15-20 years | Moderate | Flexible, easier installation | Less resistant to foot traffic |
| EPDM (Rubber) | 20-25 years | Low | Lightweight, easy repairs | Can be vulnerable to punctures |
| TPO | 15-20 years | Moderate | Reflective, energy efficient | Relatively new, limited track record |
Environmental and Energy Considerations
Traditional BUR roofing materials like asphalt and coal tar are petroleum-based, raising environmental concerns. However, many modern BUR systems incorporate low-VOC bitumen and recyclable surfacing materials. Reflective gravel or mineral tops can also enhance energy efficiency by reducing heat absorption, lowering cooling costs for buildings.
Choosing the Right Contractor for BUR Roofing
Installing or repairing a BUR roof requires specialized skills due to the layering and handling of hot bitumen. Property owners should select licensed and experienced roofing contractors familiar with BUR systems. Verify past project references and ensure the contractor adheres to local building codes and safety standards.