Overview of Built-Up Bituminous Roofing
Built-up bituminous roofing, commonly known as BUR roofing, is a durable and effective roofing system widely used in commercial and industrial buildings in the United States. This roofing method involves multiple layers of bitumen alternated with reinforcing fabrics, creating a watertight and resilient roof membrane. BUR roofing combines strength, weather resistance, and longevity, making it a preferred choice for flat or low-slope roofs.
| Feature | Description |
|---|---|
| Material | Asphalt-based bitumen with reinforcing fabrics (felt) |
| Application | Hot or cold applied layers for flat/low-slope roofs |
| Lifespan | 15 to 30 years depending on maintenance and climate |
| Advantages | Waterproof, fire resistant, UV resistant, and robust |
| Common Uses | Commercial buildings, warehouses, institutional roofs |
What Is Built-Up Bituminous Roofing?
Built-up bituminous roofing is a multi-layered roofing system made by alternately applying layers of bitumen (asphalt or coal tar) with reinforcing fabrics such as felt or fiberglass mats. These layers are then sealed with a protective surface coating, such as gravel, mineral granules, or reflective coatings.
This construction provides a strong, waterproof barrier that excels at protecting roofs against harsh weather and UV radiation. BUR roofs are especially advantageous for flat or low-pitch roofs where water drainage is minimal and traditional shingles are less effective.
Components of Built-Up Bituminous Roofing Systems
| Component | Purpose |
|---|---|
| Bitumen (Asphalt or Coal Tar) | Binds layers and provides waterproofing |
| Roofing Felts (Fiberglass or Organic) | Reinforces layers for tensile strength and durability |
| Surfacing Materials (Gravel, Mineral Aggregate) | Protects roof from UV damage, fire, and physical wear |
| Base Sheet | Initial waterproof membrane providing adhesion |
| Insulation (optional) | Improves thermal efficiency beneath the membrane |
Installation Process of Built-Up Bituminous Roofing
The installation of BUR roofing involves several key steps, typically performed by professional roofing contractors because of the complexity and use of heat in application.
- Surface Preparation: The existing roof deck is cleaned and repaired to ensure a smooth, dry base.
- Base Sheet Installation: A base sheet is fastened or adhered to the roof deck as the first waterproofing layer.
- Laying Bitumen and Felt Layers: Multiple alternating layers of hot-applied bitumen and roofing felts are rolled out and bonded together.
- Applying the Surfacing Layer: A protective top layer such as gravel is broadcast onto the final hot bitumen layer for UV resistance and durability.
- Inspection and Quality Checks: The completed roofing assembly is inspected for proper adhesion and coverage.
This layered method improves the roof’s ability to withstand water intrusion, weather extremes, and mechanical damage.
Advantages of Built-Up Bituminous Roofing
- Durability: BUR roofing can last 15-30 years with proper maintenance due to its multiple protective layers.
- Waterproofing Excellence: The overlapping bitumen and felt layers create a continuous, impermeable surface.
- Fire Resistance: Many built-up roofing systems are fire rated because of the mineral surfacing applied.
- Resilience to Weather: BUR roofs endure temperature fluctuations, heavy rain, snow, and UV radiation.
- Low Maintenance: These roofs require infrequent maintenance compared to other flat roof systems.
Common Applications of Built-Up Bituminous Roofing
BUR roofing is primarily used on flat or low-slope roofs in various sectors because of its robustness and cost-effectiveness.
- Commercial Buildings: Office complexes and malls benefit from BUR roofs’ long service life and durability.
- Industrial Facilities: Factories and warehouses favor BUR systems for their strong water and chemical resistance.
- Institutional Buildings: Schools and hospitals use BUR roofing for reliable waterproofing and fire resistance.
Maintenance Tips for Built-Up Bituminous Roofing
Regular inspections and maintenance extend BUR roofing lifespan and performance.
- Routine Inspections: Check for cracks, blisters, or gravel displacement twice a year and after severe weather.
- Clean Surface: Remove debris and dirt to prevent ponding water and damage to the membrane.
- Prompt Repairs: Address tears, punctures, or seam failures immediately to prevent leaks.
- Re-Coating: Apply new protective coatings every few years to enhance UV and weather resistance.
Comparing Built-Up Bituminous Roofing With Other Roofing Options
| Feature | Built-Up Bituminous Roofing | Modified Bitumen Roofing | Single-Ply Membrane Roofing |
|---|---|---|---|
| Construction | Multiple layers of bitumen and felt | Modified bitumen sheets with polymers | Synthetic single-layer membranes (TPO, EPDM) |
| Durability | 15-30 years | 20-25 years | 15-20 years |
| Installation Complexity | Complex, hot-applied process | Less complex, can be torch-applied or cold-applied | Quick, often adhered or ballasted |
| Cost | Moderate to high | Moderate | Varies, sometimes lower |
| Maintenance | Low to moderate | Moderate | Moderate to high |
Environmental Impact and Sustainability
Modern BUR roofing systems consider environmental factors by incorporating recycled materials such as reclaimed asphalt or recycled roofing felts. The long service life of BUR roofing reduces waste and replacement frequency, contributing to sustainability. Reflective surfacing options also improve energy efficiency by reducing heat absorption and lowering cooling costs.
Cost Considerations for Built-Up Bituminous Roofing
Installation costs for BUR roofing typically range from $3 to $7 per square foot depending on the number of layers, type of bitumen, roof size, and complexity. Although upfront costs are moderate to high compared to some roofing types, the durability and minimal maintenance costs offer long-term value.
Choosing BUR roofing balances initial investment with reliable, long-lasting protection critical for flat and low-slope commercial buildings.