Commercial Asphalt Roof

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Commercial Asphalt Roof – Commercial buildings need roofing systems that balance durability, affordability, and performance. One of the most widely used solutions across offices, retail centers, warehouses, and multifamily properties is commercial asphalt roofing. Known for its versatility and proven track record, asphalt-based roofing systems have protected low-slope and flat commercial structures for decades.

Whether you’re planning a new installation, budgeting for a replacement, or comparing roofing materials, understanding how commercial asphalt roofing works will help you make a smarter long-term investment.

What Is Commercial Asphalt Roofing?

Commercial asphalt roofing refers to roofing systems that use asphalt (bitumen) as the primary waterproofing material. Unlike residential asphalt shingles, commercial asphalt roofs are typically designed for low-slope or flat roofs and are installed in layered systems for enhanced durability.

These systems are engineered to handle:

  • Heavy foot traffic from maintenance crews

  • Mechanical equipment loads (HVAC units, vents, skylights)

  • Large roof surface areas

  • Extreme weather conditions

The most common types of commercial asphalt roofing include:

  1. Built-Up Roofing (BUR)

  2. Modified Bitumen Roofing

Built-Up Roofing (BUR) Systems

Built-Up Roofing, often called a “tar and gravel” roof, is one of the oldest and most trusted commercial asphalt roofing systems. It consists of multiple layers of asphalt and reinforcing fabrics, creating a thick, waterproof membrane.

Key Components of BUR

A typical BUR system includes:

  • Roof deck (structural base)

  • Insulation layer

  • Base sheets

  • Multiple plies of felt or fiberglass mats

  • Hot-applied asphalt between layers

  • Protective surfacing, often gravel or mineral cap sheets

Advantages of BUR

1. Excellent Waterproofing
The multiple layers create redundancy. If one layer fails, others still protect the building.

2. Strong UV Protection
Gravel surfacing shields the asphalt from sun damage, extending roof life.

3. Proven Longevity
Properly installed BUR systems can last 20–30 years or more with regular maintenance.

4. Fire Resistance
Gravel surfaces also enhance fire resistance, an important safety benefit for commercial properties.

Considerations

BUR systems are heavier than many modern roofing options. The building structure must be able to support the load. Installation can also be labor-intensive and involve hot asphalt, which requires experienced crews.

Modified Bitumen Roofing

Modified bitumen is an evolution of BUR technology. It uses asphalt modified with rubber or plastic polymers to improve flexibility and performance.

There are two primary types:

SBS (Styrene-Butadiene-Styrene)

  • Rubber-like flexibility

  • Performs well in cold climates

  • Resists cracking from building movement

APP (Atactic Polypropylene)

  • Plastic-like durability

  • Better resistance to UV rays

  • Often installed with torch-applied methods

Installation Methods

Modified bitumen systems can be installed using:

  • Torch-applied

  • Cold adhesives

  • Self-adhered sheets

  • Hot asphalt

This flexibility allows contractors to choose methods that best suit building conditions and safety requirements.

Advantages of Modified Bitumen

1. High Flexibility
Handles temperature changes and structural movement better than traditional BUR.

2. Durable Surface Options
Granulated cap sheets protect against UV rays and weathering.

3. Easier Repairs
Damaged sections can often be patched without major tear-offs.

4. Multi-Layer Protection
Like BUR, modified bitumen is installed in layers for added redundancy.

Lifespan typically ranges from 20–25 years, depending on maintenance and climate.

Why Commercial Asphalt Roofing Is So Popular

Despite the rise of single-ply membranes, asphalt systems remain popular for several reasons.

Cost-Effective Performance

Commercial asphalt roofing offers a strong balance between upfront cost and long-term value. While not always the cheapest option initially, its durability and repairability often result in lower lifetime expenses.

Proven Track Record

Asphalt-based roofs have been used for over a century. Manufacturers like GAF and CertainTeed have continually refined asphalt roofing technologies for commercial use.

Multi-Layer Protection

Unlike single-layer systems, asphalt roofs use multiple plies. This redundancy is a major advantage in protecting against leaks.

Excellent Waterproofing

Asphalt is naturally water-resistant. When layered, it forms a continuous, durable waterproof barrier.

Performance in Different Climates

Cold Climates

SBS-modified bitumen performs exceptionally well in freezing temperatures due to its flexibility. It resists cracking caused by contraction and expansion.

Hot and Sunny Regions

APP-modified bitumen and BUR with reflective surfacing help reduce UV degradation. Light-colored cap sheets can also improve energy efficiency.

Wet and Storm-Prone Areas

The layered design of asphalt roofing provides strong resistance to heavy rain and ponding water when proper drainage is in place.

Installation Process Overview

Although exact steps vary, most commercial asphalt roofing installations include:

  1. Tear-Off or Preparation
    Old materials may be removed, or the existing roof prepared for overlay.

  2. Deck Inspection and Repair
    The structural deck is checked for damage or moisture.

  3. Insulation Installation
    Rigid insulation boards improve energy performance.

  4. Base Sheet Application
    Acts as the foundation for the roofing system.

  5. Membrane Layering
    Multiple layers of asphalt and reinforcement are applied.

  6. Cap Sheet or Surfacing
    Granulated sheets or gravel provide UV and impact protection.

Professional installation is critical. Improperly sealed seams or flashing details can lead to leaks regardless of material quality.

Maintenance Requirements

Commercial asphalt roofs are durable, but they are not maintenance-free.

Routine Maintenance Should Include:

  • Biannual inspections (spring and fall)

  • Checking for blisters, cracks, or punctures

  • Clearing debris and drainage systems

  • Inspecting flashing around penetrations

  • Prompt repairs of minor damage

Well-maintained asphalt roofs often exceed their expected lifespan.

Common Problems and Repairs

Even strong systems can develop issues over time.

Blistering

Air or moisture trapped between layers can cause bubbles. Small blisters may be monitored; larger ones require repair.

Alligatoring

Surface cracking resembling reptile skin often signals aging asphalt and UV damage.

Ponding Water

Flat roofs must drain properly. Long-term ponding can weaken the membrane.

Flashing Failures

Most leaks occur at edges, seams, or penetrations rather than in the field of the roof.

Repairs typically involve patching with compatible asphalt materials, making commercial asphalt systems relatively easy to maintain compared to some alternatives.

Energy Efficiency Considerations

While traditional asphalt is dark and absorbs heat, modern systems can be made more energy-efficient.

Options include:

  • Reflective cap sheets

  • Light-colored mineral surfacing

  • Improved insulation beneath the membrane

Some systems compete with reflective membranes offered by companies like Firestone Building Products in terms of energy performance when designed properly.

When Is Commercial Asphalt Roofing the Best Choice?

Asphalt systems are ideal for:

  • Large flat or low-slope commercial roofs

  • Buildings with frequent rooftop maintenance traffic

  • Projects needing proven, long-term waterproofing

  • Owners who prefer repairable, layered systems over single membranes

They are particularly well-suited for schools, hospitals, retail centers, and industrial buildings.

Lifespan and Replacement Timing

Typical lifespan ranges:

  • BUR systems: 20–30+ years

  • Modified bitumen: 20–25 years

Signs it may be time for replacement:

  • Widespread cracking or surface deterioration

  • Frequent leaks despite repairs

  • Insulation saturated with moisture

  • Flashing failures across multiple areas

A professional roof inspection can determine whether repairs or full replacement is more cost-effective.

Final Thoughts

Commercial asphalt roofing remains one of the most dependable solutions in the roofing industry. Its layered construction, strong waterproofing properties, and long service life make it a smart investment for many commercial property owners.

While newer materials have entered the market, asphalt-based systems continue to prove their value through durability, repairability, and decades of real-world performance. When installed by experienced professionals and maintained regularly, a commercial asphalt roof can protect your building reliably for decades.

If you manage or own a commercial property, understanding these systems gives you the confidence to plan budgets, evaluate contractor proposals, and choose a roofing solution that delivers both performance and peace of mind.