Asphalt Built-Up Roof (BUR) systems have been a trusted roofing solution for decades, known for their durability, weather resistance, and cost-effectiveness. This roofing method involves multiple layers of asphalt and reinforcing fabrics, creating a robust barrier against environmental elements. Understanding the structure, benefits, installation process, and maintenance of asphalt built-up roofs is essential for homeowners and business owners seeking long-lasting roofing options. This guide covers everything needed to make an informed decision about BUR roofing.
| Aspect | Details |
|---|---|
| Roofing Type | Asphalt Built-Up Roofing (BUR) |
| Material Layers | Multiple layers of asphalt, felt, and reinforcing fabrics |
| Typical Lifespan | 15-30 Years |
| Common Applications | Flat or low-slope commercial and residential roofs |
| Key Benefits | Durability, waterproofing, UV resistance, fire resistant |
What Is Asphalt Built-Up Roofing (BUR)?
Asphalt Built-Up Roofing, commonly known as BUR, is a traditional flat or low-slope roofing system composed of alternating layers of asphalt and reinforcing felts. Each layer is carefully applied to form a laminated roof membrane. The asphalt acts as a waterproofing agent, while the felts provide strength and flexibility. The topmost layer often includes a protective surface such as gravel or a reflective coating to shield the roof from ultraviolet rays and weather conditions.
This method is widely recognized for its reliability in protecting buildings against water intrusion and weather extremes, making it a preferred choice for many commercial structures and some residential buildings with flat roofs.
Components and Materials of Asphalt Built-Up Roof
Asphalt
Asphalt serves as the adhesive and waterproofing agent in BUR systems. It is a byproduct of petroleum refining and is available in hot-applied or cold-applied formulations. Hot asphalt is heated to a liquid state before application, ensuring strong bonding and seamless waterproofing.
Roofing Felts
Roofing felts are layers of reinforcing fabric, generally made from organic materials or fiberglass. These felts are impregnated with asphalt and act to increase rigidity and tear resistance.
Surfacing Materials
The final layer includes various surfacing materials like gravel, mineral granules, or reflective coatings. These protect the roof membrane from mechanical damage, UV degradation, and improve fire resistance.
Additional Materials
- Insulation board: Sometimes installed beneath the BUR assembly to improve thermal performance.
- Reinforcement fabrics: Such as glass fiber mats for added strength and flexibility.
Advantages of Asphalt Built-Up Roofing
- Durability: BUR systems offer excellent durability and can last 15 to 30 years with proper maintenance.
- Waterproofing Excellence: Multiple layers allow for superior protection against water penetration.
- UV and Fire Resistance: Surfacing layers like gravel provide a shield from ultraviolet rays and reduce fire hazards.
- Low Maintenance: Built-up roofs require minimal maintenance compared to other roofing types.
- Cost-Effective: Initial costs are reasonable, especially for large flat roof areas, offering long-term value for money.
Common Applications of Asphalt Built-Up Roofing
BUR systems are predominantly used on commercial buildings with expansive flat or low-slope roofs. They are also suitable for multi-family residential buildings, warehouses, and institutional facilities.
The adaptability of BUR to various roof shapes and sizes, combined with its strength and longevity, makes it a favored choice for these settings.
Installation Process of Asphalt Built-Up Roofing
Installing a BUR system requires skilled professionals familiar with the heating and layering of asphalt and felts. The process typically involves:
- Preparation of the roof deck, ensuring a clean, dry, and structurally sound surface.
- Applying multiple alternating layers of hot asphalt and felt (usually 3-5 plies).
- Adding a gravel or mineral granule surface to protect the underlying layers.
- Ensuring proper flashing at roof edges, penetrations, and joints to prevent leaks.
Installation quality is crucial for the BUR’s longevity and waterproofing capabilities.
Maintenance and Repair of Asphalt Built-Up Roofs
Regular inspections are vital for detecting damage such as cracks, blistering, or gravel displacement. Maintenance typically involves:
- Clearing debris to prevent water pooling.
- Replacing lost or damaged gravel surfacing.
- Repairing minor punctures or tears with asphalt patches.
- Sealing flashings and joints to maintain a watertight seal.
Prompt repairs extend the service life and reduce the risk of costly water damage.
Environmental and Energy Considerations
Modern BUR systems can incorporate reflective coatings to reduce heat absorption, contributing to lower cooling costs. Additionally, the materials used are increasingly recyclable.
Environmental benefits include reducing the urban heat island effect and extending the lifecycle of roofing materials, supporting sustainable building practices.
Comparing Asphalt Built-Up Roofs to Other Flat Roofing Systems
| Roof Type | Durability | Installation Complexity | Cost | Maintenance |
|---|---|---|---|---|
| Asphalt Built-Up Roofing (BUR) | 15-30 Years | Moderate | Moderate | Low to Moderate |
| Modified Bitumen Roofing | 15-20 Years | Moderate | Moderate to High | Low |
| EPDM Rubber Roofing | 20-30 Years | Low | Moderate | Low |
| TPO (Thermoplastic Polyolefin) Roofing | 15-25 Years | Low to Moderate | Moderate | Low |
Cost Factors Affecting Asphalt Built-Up Roofing
The total cost of a BUR installation depends on several factors:
- Roof size and complexity: Larger or irregularly shaped roofs increase material and labor costs.
- Material quality: Premium materials such as fiberglass felts or higher-grade asphalt add to expenses.
- Labor rates: Skilled labor requirements impact overall installation cost.
- Geographic location: Local climate and material availability influence pricing.
- Maintenance needs: Regular upkeep can incur ongoing costs.
Budgeting carefully for upfront installation and long-term maintenance ensures effective investment in BUR roofing.
Key Considerations Before Choosing Asphalt Built-Up Roofing
- Assess roof slope suitability as BUR performs best on flat or low-pitch roofs.
- Consider the building’s load capacity due to BUR’s weight, especially with gravel surfacing.
- Evaluate local climate effects, particularly in areas with extreme heat or heavy rainfall.
- Confirm contractor expertise in BUR installation for quality assurance.
- Plan for periodic maintenance and professional inspections.
These factors help ensure BUR roofing meets expectations for durability, protection, and cost-effectiveness.