Asphalt Built Up Roofing: A Comprehensive Guide

Aphalt Built Up Roofing refers to a traditional roofing system that combines multiple tar and asphalt layers with reinforcing fibers, topped by stone granules. This method creates a durable, weather-resistant surface commonly used on flat or low-slope roofs. The combination of waterproof membranes and protective aggregates provides reliability in varied climates. This guide explains the structure, benefits, installation, maintenance, and troubleshooting of asphalt built up roofing to help homeowners and builders make informed decisions.

Note: Asphalt built up roofs are valued for their long track record, cost efficiency, and versatility in drainage configurations. The following sections highlight key considerations, from material choices to seasonal maintenance, ensuring the system performs effectively over time.

What Is Asphalt Built Up Roofing

Asphalt built up roofing (BUR) is a composite roofing system that layers hot asphalt or coal tar pitch with reinforcing plies, typically polyester or fiberglass felts. Each ply adds strength, while the final layer is a reflective or mineral-surfaced cap sheet. The finished system is designed to resist water intrusion on flat or low-pitch structures and to endure typical U.S. weather patterns.

The core advantage of BUR lies in its redundancy: if one layer is compromised, others continue to provide protection. The system can be customized with ply configurations, torch-down or cold-applied adhesives, and cap sheets to match project requirements and local codes.

Key Materials And Layers

The typical BUR assembly includes several essential components. First, a roof deck provides a solid base. A vapor barrier may be installed to control moisture movement. Then multiple plies of reinforcing felt are saturated with hot asphalt or coal tar pitch. A surfacing layer—either mineral granules or reflective coating—finishes the system and protects against ultraviolet exposure.

Common ply configurations range from three to five plies, with additional layers used for enhanced durability or for roofs with steeper sub-pitches. Cap sheets may be mineral surfaced for durability and protection or reflective for energy savings. The exact composition depends on climate, building codes, and performance goals.

Benefits And Drawbacks

Benefits include strong waterproofing with multiple protective layers, proven performance in broad climates, exceptional puncture resistance, and a relatively long service life when properly maintained. BUR roofs can be repaired in localized areas without complete replacement, which reduces long-term costs. They also perform well on flat and low-slope roofs where drainage can be challenging.

Drawbacks involve heavier weight, higher installation labor, odor from hot asphalt during installation, and potential environmental concerns with coal tar in some formulations. Maintenance is essential to prevent asphalt oxidation and to monitor membrane seams for leaks. In modern construction, BUR competes with single-pply membranes and fluid-applied systems depending on project requirements.

Installation Process Overview

Installation begins with surface preparation, including cleaning, flashing critical penetrations, and installing a prime coat if specified. The process then advances through several plies of felt, each saturated with hot asphalt or adhesive. The final layer is a cap sheet, which may be mineral surfaced or reflective. Some projects use cold-applied adhesives for safer handling and reduced odors. Proper ventilation and safety practices are mandatory due to hot materials and fumes.

Quality control is critical at every step. The installer should ensure uniform asphalt saturation, correct ply alignment, and seamless transitions at edges and terminations. Joints and flashings require careful detailing to prevent leaks around chimneys, skylights, and roof penetrations.

Maintenance And Longevity

Regular maintenance extends BUR life. Periodic inspections after severe weather help identify issues such as blisters, cracks, or membrane lifting. Cleaning debris from the surface and ensuring proper drainage prevents standing water and membrane degradation. Re-surfacing or applying a new cap sheet at recommended intervals can restore weatherproofing and extend service life.

Professional inspections every 3–5 years, or after major storms, are common practice. Prompt repairs of blisters, splits, or punctures preserve insulation performance and reduce the risk of leaks. Documentation of maintenance history aids in planning future replacements and budgeting for capital expenditures.

Common Issues And Troubleshooting

Typical problems include blisters arising from trapped moisture, punctures from foot traffic or impacts, and edge leaks where the cap sheet fails to shed water properly. Poor adhesion between plies can lead to delamination, reducing the system’s structural integrity. Improper flashing around edges or penetrations commonly causes leaks.

Troubleshooting tips include localized patching for small damage, resealing problematic seams, and restoring drainage paths. If widespread deterioration is detected, a full or partial re-cover with a new BUR assembly may be necessary. Always consult a qualified roofer to assess roof condition and recommended remediation strategies.

Climate Considerations And Performance

BUR is adaptable to diverse climates, but local conditions influence the design. In hot climates, reflective cap sheets or cooling coatings can reduce heat gain. In cold regions, extra attention to insulation and ice dam considerations is important. In coastal areas, bonds and seals must resist humidity and salt exposure. Wind uplift resistance is enhanced by proper attachment and edge detailing.

Environmental And Energy Considerations

Older BUR systems may utilize coal tar pitch, raising environmental and health concerns. Modern BUR installations often replace coal tar with safer asphalt blends. Reflective cap sheets and cool coatings can improve energy efficiency by reducing cooling loads. Proper disposal of old roofing materials complies with local environmental regulations, and the choice of recyclable components can influence a project’s sustainability profile.

Cost Considerations And Budgeting

Cost for asphalt built up roofing varies with ply count, cap sheet choice, roof complexity, and labor rates. A higher ply count provides greater durability but increases upfront costs. Maintenance costs over the system’s life, including periodic resealing and potential re-coverings, should be weighed against the expected service life. For comparative purposes, BUR often presents a mid-range option relative to single-ply membranes and built-up systems with alternative coverings.

Choosing A Roofing Contractor

Selecting a qualified contractor is crucial for BUR performance. Look for licenses, insurance, and a portfolio of BUR installations. Confirm the contractor’s familiarity with local building codes, climate considerations, and required permits. Request written proposals detailing ply configurations, cap sheet types, warranty terms, and expected timelines. Ask for references and verify completed projects similar in size and exposure to your roof.

In summary, asphalt built up roofing offers robust waterproofing through layered construction, versatility for flat and low-slope roofs, and a range of customization options. Understanding the material makeup, installation practices, and maintenance needs helps ensure a long-lasting, reliable roof that performs well in U.S. climates.