Built Up Roof Materials: Types, Pros, Cons, and Installation

Built up roof materials, commonly known as BUR systems, have stood the test of time for commercial and some residential applications in the United States. This guide explains what BUR is, the typical layers involved, the main material options, and practical considerations for installation, maintenance, and longevity. Understanding the strengths and limitations of built up roofs helps property owners choose the right system for climate, budget, and performance goals.

What Is Built Up Roof Material?

Built up roof material is a multi-layer roofing system composed of alternating waterproofing and reinforcing plies that are adhered or hot-mopped together to form a durable, seamless surface. Traditionally, three or more plies are combined with bitumen binders, often finished with a surface cap sheet or mineral granules. BUR systems offer excellent waterproofing, UV resistance, and proven performance in severe weather. The overall assembly is designed to resist wind uplift and provide long service life when properly installed and maintained.

Common Layers In Built Up Roofing

A typical BUR assembly includes four core components: a roof deck, reinforcing plies, bitumen asphalt or coal tar pitch, and a surface surfacing layer. Reinforcing plies are usually fiberglass or organic felts. The bitumen acts as the waterproofing binder, while the surface layer may be mineral granules, smooth gravel, or reflective coatings. Enhanced BUR configurations may incorporate interply sheets for extra waterproofing or insulation boards for thermal efficiency. The finished surface protects against solar radiation, foot traffic, and weathering.

Material Options And Their Pros And Cons

Built up roofs primarily rely on bitumen-based waterproofing, with two common binders: asphalt and coal tar pitch. Asphalt BUR is cost-effective, readily available, and easy to repair, but it can be softer in high heat and may require reflective coatings to improve energy performance. Coal tar pitch offers superior longevity and chemical resistance, yet it raises health and odor concerns during installation and has more stringent handling requirements. Some modern BUR systems use modified bitumen or polymer-modified asphalt for enhanced performance. Each option affects installation methods, temperature sensitivity, and maintenance needs.

Important performance considerations include:

• Wind uplift resistance: BUR systems are designed to resist high winds, particularly with a properly attached base sheet and a strong cap layer.
• Thermal performance: Insulation and reflective cap options reduce heat transfer and energy use in hot climates.
• Maintenance: BUR requires periodic inspection and prompt patching of blisters, splits, or lifting edges to prevent water intrusion.

Installation Considerations And Safety

Installation of built up roofs involves skilled trades and careful sequencing. The deck must be clean and dry, with proper ventilation where needed. Plies are installed using hot asphalt or cold adhesives, depending on the system and climate. The cap sheet or granule finish provides UV protection and walking surface. Weather constraints are critical; hot asphalt must be applied at temperatures above a threshold to ensure proper adhesion. Safety protocols include personal protective equipment, ventilation for tar fumes, and fall protection for crews working at height.

Key steps in BUR installation include:

• Preparing and cleaning the substrate
• Applying the first bitumen-containing base sheet
• Adding reinforcing plies with adhesive or mopping process
• Sealing edges, penetrations, and terminations
• Applying cap sheet and surface finish

Contractors should follow manufacturer specifications, local building codes, and fire rating requirements. A successful installation minimizes leaks, limits odor exposure, and safeguards long-term performance.

Maintenance And Longevity

Regular inspection is essential to extend BUR life. Schedule annual or semi-annual checks for blisters, membrane lifting, cracks, and ponding water. Address issues promptly with patching, resealing, or replacing compromised plies. Clean the surface from debris and ensure drainage is unobstructed. When repairs become frequent or extensive, a system upgrade to another BUR composition or a different roof type may be warranted. A properly maintained BUR can last 20 to 40 years, depending on climate, ventilations, and maintenance rigor.

Durability is influenced by:

• Climate exposure: UV intensity, temperature swings, and precipitation patterns affect aging.
• Installation quality: Proper adhesion and ply layering prevent premature failures.
• Maintenance regime: Timely repairs prevent water intrusion and structural damage.

Sustainability And Recyclability

BUR systems have environmental considerations. Bitumen emissions, energy use during production, and the lifecycle impacts of roof replacements are factors for owners aiming for sustainability. Some manufacturers offer reflective caps to reduce cooling loads, while recycled or reclaimable components are increasing in availability. When possible, choosing long-life BUR configurations and efficient installation practices can lower overall environmental impact and maintenance needs over the roof’s lifespan.

Common Applications And Performance Considerations

Built up roofs are widely used on commercial buildings, warehouses, and schools due to their durability, impermeability, and proven performance. They perform well in areas with heavy rainfall, ice damming risks, and the need for a rugged walking surface. For residential flat roofs or retrofit projects, BUR is less common but may be found in some retrofits where traditional materials are preferred. When selecting BUR, consider building codes, fire ratings, energy efficiency goals, and life-cycle costs to determine the best material and configuration for the project.

Cost Considerations And Budgeting

Initial costs for BUR installations vary based on material choice, ply count, and surface finish. Coal tar pitch systems tend to have lower upfront material costs but higher handling and odor considerations. Asphalt-based BUR is typically more affordable upfront and easier to work with. Long-term expenses include maintenance, potential energy savings from reflective surfaces, and eventual re-roofing or system upgrades. A well-planned maintenance schedule reduces the total cost of ownership over the roof’s life.

Selecting A Contractor And Quality Assurance

Choose a licensed roofing contractor with BUR experience and a track record of successful projects. Request a written scope, warranty details, and references. Verify that crews hold current safety certifications and that the installation follows manufacturer specifications and local codes. A thorough inspection plan, documented workmanship, and a clear warranty help ensure confidence in the finished roof.

Key Takeaways

• BUR systems provide robust waterproofing with multi-ply construction and durable cap finishes.
• Material choice (asphalt vs coal tar) affects heat performance, odor, and longevity, requiring careful evaluation.
• Professional installation and diligent maintenance are critical for maximizing service life.