Built-Up Roofing (BUR) is one of the oldest and most time-tested commercial roofing systems in use today. Often referred to as "tar and gravel" roofs, BUR systems have been trusted by property owners for over a century, particularly for flat or low-slope roofs. They are known for their durability, water resistance, and ability to withstand harsh weather conditions. Let's explore everything you need to know about BUR roofing—from what it is and how it works, to its benefits, drawbacks, installation process, maintenance tips, and how it compares to modern alternatives.

What Is a Built-Up Roof System?

A built-up roof consists of multiple layers of bitumen (asphalt or coal tar) alternated with reinforcing fabrics, commonly called "plies." These layers are topped with a final surfacing material such as gravel, slag, or a reflective coating to protect the system from UV rays, temperature extremes, and mechanical damage.

Typical components of a BUR system include:

• Base sheet: Installed over the roof deck as the foundation layer
• Bitumen layers: Hot-applied asphalt or coal tar pitch
• Reinforcement plies: Layers of felt, fiberglass, or polyester fabric
• Surfacing: Gravel, mineral cap sheet, or reflective coating

Depending on building needs, a BUR may include 3 to 5 plies or more, creating a redundant, watertight membrane system.

Key Benefits of Built-Up Roofing

BUR systems offer several proven advantages that make them ideal for commercial properties:

Proven Longevity

Built-up roofs have a proven track record spanning 100+ years. With proper maintenance, BUR systems can last 20–30+ years, depending on climate, foot traffic, and installation quality.

Excellent Waterproofing

Multiple plies create a thick, watertight barrier that performs exceptionally well under standing water, snow loads, and heavy rainfall. Each layer adds redundancy, making it less likely to leak compared to single-ply systems.

UV and Heat Resistance

The top layer of gravel or a reflective coating protects the system from harmful UV rays and minimizes thermal cycling damage, which helps extend the roof's lifespan.

Fire Resistance

BUR systems, especially those with mineral-surfaced cap sheets or gravel, offer excellent fire resistance. Many BUR systems meet Class A fire ratings.

Sound and Impact Dampening

The thickness of the built-up system provides excellent soundproofing and can reduce the noise of rain, hail, and rooftop equipment. It also offers superior protection from foot traffic and mechanical impacts.

Common Drawbacks of BUR Systems

While BUR roofing systems offer many benefits, they aren't ideal for every situation. Here are a few limitations to consider:

Heavier Weight

Because BUR involves multiple layers of asphalt and aggregate, it's significantly heavier than systems like TPO or EPDM. Some older structures may require structural reinforcement before installation.

More Complex Installation

BUR installation is labor-intensive and requires specialized skills. It also involves hot asphalt or coal tar, which means longer installation times, fumes, and potential job-site safety concerns. However, experienced professionals (like those at Applied Roofing Solutions) can complete even the most complex jobs to industry-leading standards. 

Higher Initial Cost

Upfront costs for BUR are generally higher than for single-ply systems. However, when factoring in lifespan and durability, it can offer a strong return on investment.

Difficult Repairs

Detecting and repairing leaks in a BUR system can be more challenging than with a single-ply roof, especially without proper documentation or inspection history. However, this is also no problem for trusted, experienced BUR specialists (like those at Applied Roofing). 

Installation Process of a BUR System

Installing a BUR roof involves several key steps, including:

Step 1: Deck Preparation

The existing roof is removed (if necessary), and the surface is cleaned, dried, and prepped. A base sheet is fastened to the deck to serve as the first layer.

Step 2: Bitumen Application

Hot asphalt or coal tar is applied to bond each layer. The bitumen is heated in a kettle and spread evenly across the roof between each ply.

Step 3: Reinforcement Plies

Felt or fiberglass plies are embedded into the hot bitumen layer by layer. Most BUR systems use at least three plies, though some may use more for added durability.

Step 4: Surfacing

Once the desired number of plies is installed, the system is finished with a protective top layer—typically gravel, mineral cap sheets, or a UV-reflective coating. This surfacing enhances durability, UV protection, and fire resistance.

Maintenance and Lifespan Tips

To ensure your BUR system reaches its full lifespan potential, follow these maintenance best practices:

• Inspect the roof at least twice per year, preferably in spring and fall
• Check after storms for signs of ponding water, gravel displacement, and flashing issues
• Clean debris from drains and gutters to prevent water buildup
• Monitor high-traffic areas near HVAC units, skylights, or service paths for surface wear
• Promptly repair small cracks or splits as part of your maintenance plan to prevent larger water intrusion problems

Is BUR Right for Your Building?

BUR roofing is an excellent choice for many types of commercial, industrial, and institutional buildings, especially when durability, longevity, and fire resistance are top priorities. It is ideal for:

• Flat or low-slope roofs
• Buildings with heavy foot traffic
• Areas with intense sun, snow, or storm exposure
• Facility managers planning for long-term roof ROI

However, it may not be ideal for lightweight structures, quick installations, or odor-sensitive environments due to the hot asphalt fumes during application. 

Built-Up Roofing has remained a trusted commercial roofing system for over a century—and for good reason. Its layered construction offers unmatched protection, weather resistance, and longevity. While installation is more complex and costly than some modern systems, BUR pays off in durability, energy efficiency, and low risk of early failure.

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Choose Applied Roofing Solutions BUR Installation

Applied Roofing Solutions is your trusted source of BUR installation. We proudly serve businesses near Reidsville, Burlington, Eden, Graham, Danville, Martinsville, Stanleytown, Patrick Springs, and beyond. 

For business owners seeking a rugged, long-lasting roof with a proven track record, BUR continues to be one of the best investments available in commercial roofing. Our specialists invite you to explore our portfolio or contact our commercial roofing professionals to get started today!

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