Comprehensive Guide to Asphalt Built-Up Roofs for Durable Roofing Solutions

Asphalt Built-Up Roofs (BUR) remain a popular choice for commercial and residential flat roofing due to their durability and cost-effectiveness. This roofing system combines layers of asphalt and reinforcing fabrics to create a robust, waterproof barrier. Understanding its components, installation process, benefits, and maintenance is crucial for property owners looking for reliable flat roofing solutions. This article delves deep into the details of asphalt built-up roofs, exploring every aspect to provide a thorough understanding for American homeowners, contractors, and facility managers.

What Is an Asphalt Built-Up Roof?

Asphalt Built-Up Roofs (BUR) are traditional roofing systems consisting of multiple layers of asphalt alternated with reinforcing fabrics such as fiberglass or organic felts. Also known as “tar and gravel roofs,” these layers are assembled on flat or low-sloped roofs to create a durable, waterproof membrane. The top layer is often finished with gravel or mineral granules to protect against UV radiation and weathering.

This roofing type traces back over a century, valued for its simplicity, reliability, and strong resistance to water infiltration. Its layered construction provides redundancy, making it highly resilient compared to single-layer solutions.

Core Components of Asphalt Built-Up Roof Systems

Asphalt

Asphalt acts as the adhesive and waterproofing agent in BUR systems. Available in hot-applied or cold-applied formulations, it binds roofing felts and creates a continuous waterproof barrier. The quality of asphalt, including modifiers for flexibility and temperature resistance, impacts the roof’s longevity and performance.

Reinforcing Fabrics (Felts)

Felt layers enhance the roof’s structural integrity. They are typically made from organic materials (like cellulose) or fiberglass mats. Fiberglass felts offer superior resistance to fire and moisture compared to organic felts, though they may be costlier.

Surfacing Materials

• Gravel or Aggregate: Commonly used to shield the asphalt from UV rays, mechanical damage, and fire hazards.
• Mineral Granules: Sometimes embedded in the asphalt surface to provide similar protective benefits.
• Coatings: Reflective coatings can improve energy efficiency by reflecting sunlight, reducing heat absorption.

Installation Process of Asphalt Built-Up Roofs

The BUR installation must be carefully executed by experienced roofing professionals to ensure a watertight and durable result. The process typically involves:

1. Surface Preparation: Clean and inspect the roof deck to ensure it’s smooth and free of moisture or debris.
2. Applying the Base Layer: A base sheet is laid or embedded in hot asphalt to create the first waterproof barrier.
3. Layering Felts and Asphalt: Multiple plies of roofing felt are embedded in buckets of hot asphalt or cold adhesives. The number of plies varies based on design and local building codes, typically between three to five layers.
4. Adding the Surfacing Layer: After the felts are installed, loose gravel or mineral granules are applied while the asphalt is still hot. The granules protect the membrane from UV rays and mechanical wear.
5. Final Inspection: The roof is inspected for uniform thickness, coverage, and absence of defects.

Alternative Application Methods

• Cold Adhesive Application: Uses chemical adhesives instead of hot asphalt to reduce fire risk and odor.
• Torch-Applied BUR: Employs heat from a torch to melt the asphalt, aiding adhesion of layers.

Advantages of Asphalt Built-Up Roofs

Asphalt BURs combine durability with cost-efficiency and versatility:

• Water Resistance: Multi-layered construction offers excellent protection against water infiltration and ponding common on flat roofs.
• Long Lifespan: Typically, BUR systems last 15 to 30 years when installed and maintained correctly.
• Fire Resistance: Asphalt and associated materials provide a high degree of fire protection, particularly when surfaced with gravel.
• UV Protection: The gravel or mineral surface guards against ultraviolet degradation, extending the membrane’s life.
• Cost-Effective Installation: Compared to single-ply membranes, BUR roofing often offers better value for long-term durability.
• Thermal Performance: Multiple layers provide better insulation properties, reducing energy costs.

Common Drawbacks and Limitations

Even with its many benefits, asphalt built-up roofs have some drawbacks to consider:

• Weight: BUR systems are relatively heavy, requiring a strong roof deck structurally capable of supporting the added mass.
• Installation Time: The multi-layer process can be time-consuming, increasing labor costs and exposure to weather risks during application.
• Maintenance Needs: Though durable, BUR systems require regular inspections to identify and repair cracks, blisters, or other damages.
• Environmental Concerns: Uses petroleum-based materials, which may have environmental impacts in production and disposal.

Maintenance and Repair Tips for Asphalt Built-Up Roofs

Routine maintenance is essential for maximizing the lifespan of BUR roofs and preventing costly repairs. Property owners should must:

• Inspect the Roof Twice Annually: Check for signs of cracking, blistering, or edge damage.
• Clear Debris: Remove leaves, dirt, and standing water to avoid membrane degradation.
• Repair Damage Promptly: Use roofing asphalt and patches to seal blisters or punctures immediately.
• Monitor Flashings and Seals: Ensure perimeter and roof penetrations are watertight.
• Professional Inspections: Have qualified roofing contractors perform detailed checks every few years.

Cost Considerations for Asphalt Built-Up Roof Installation

Costs can vary widely depending on geographic location, roof size, and materials selected. As of recent data, BUR roofs typically cost between $4.50 to $8.00 per square foot installed.

Investing in higher-quality materials and skilled labor will typically increase upfront costs but improve durability and reduce long-term expenses.

Comparing Asphalt Built-Up Roofs With Other Flat Roofing Options

Environmental Impact and Sustainability

While BUR roofs use petroleum-based products contributing to environmental considerations, advances have been made to improve sustainability:

• Use of recycled asphalt products reduces raw material consumption.
• Reflective surfacing options decrease building cooling demand.
• Proper disposal and recycling of old BUR materials minimize landfill impact.

Property owners increasingly look for eco-friendly options during reroofing, making it essential to weigh BUR’s performance benefits against environmental concerns.

When to Choose Asphalt Built-Up Roofing

BUR roofs are best suited for:

• Flat or low-slope roofs requiring proven waterproofing and durability.
• Buildings where long-lasting fire resistance is a priority.
• Clients seeking a cost-effective roofing system with a proven track record.
• Projects where roof weight load is structurally supported.
• Maintenance access is reasonable to support periodic upkeep.

For many commercial buildings, warehouses, and some residential flat roof applications, asphalt BUR remains an ideal roofing system.