What is Built-Up Roofing

Built-up roofing (BUR) is a solution for homes with flat or low-slope roofs that has been used in the U.S. for over 100 years. Its multilayered structure, which includes asphalt, provides high resistance to even the most challenging climates. That’s why in regions like Cape Cod, this option is often used.

What is Built-Up Roofing (BUR)

Built-up roofing is used on low-slope or completely flat roofs. It gets its name from the installation method: materials are laid in multiple layers, forming a strong and watertight membrane.

Each layer (“ply”) consists of bitumen (asphalt or coal tar) alternating with reinforcing fabric. Once installation is complete, a layer of gravel is applied to protect the membrane from UV rays, hail, birds, and other potential damage.

Components of a Built-Up Roofing System

To better understand the technology, it’s important to break down the structure. Here’s how the roof is arranged layer by layer.

Base Sheet

The underlayment is the first layer laid on the roof deck, fixed with nails or adhesive. It serves as the primary waterproofing and the foundation of the entire BUR system. Various materials are used, such as fiberglass, often impregnated with asphalt for added strength and moisture resistance. Some types of underlayment are self-adhesive, while others are secured with asphalt or glue.

Bitumen

Bitumen is the key waterproofing component in the BUR system. It is applied hot to form a seamless, watertight membrane. Two types of bitumen are used: asphalt and coal tar.

Asphalt is the most popular since it combines good performance with ease of installation. There are three types based on application method: hot, cold, and mopped asphalt.
Coal tar is more moisture-resistant and is often used on roofs exposed to heavy rainfall or harsh chemicals. It has a self-healing effect — small cracks and cuts can seal themselves over time.

The lifespan of high-quality bitumen roofs can reach 40–50 years. Many experts claim that bitumen roofing is “one of the most reliable.” However, working with it carries risks: during removal or installation, roofers may suffer chemical burns to the skin, eyes, or respiratory tract. For this reason, the use of bitumen systems has been gradually declining.

Roofing Felt

Felt sheets, or roofing felts, serve as the reinforcing layer between plies of bitumen, increasing roof strength. Fiberglass mats are the most common due to their moisture resistance and compatibility with asphalt. Organic variants made from wood products, paper, or cellulose fibers are used less often because they absorb more moisture, though they are more flexible.

Surface Materials

The finishing layer is the final stage of the BUR system, designed to protect the underlying layers from mechanical damage and UV rays. Gravel is usually embedded in hot asphalt for this purpose.

There are also alternative finishes, such as mineral-surfaced roofing with granules or reflective coatings like aluminum or elastomeric layers. These not only protect from external impact but also improve energy efficiency by reflecting sunlight and reducing surface heat.

Built-Up Roofing Installation Process

Installing a BUR system is a complex process that requires specialized knowledge, skills, and equipment. It begins with inspecting and preparing the roof deck, which must be clean, dry, and structurally sound.

The first step is the underlayment layer, which is placed over the decking. Next come alternating layers of asphalt and roofing felt. The asphalt, applied hot, is spread using the mopping method, after which the felt sheets are laid. This cycle is repeated three to five times to create a multilayered roofing membrane.

The final stage is the application of the surface layer. If gravel is used, it is spread over the still-warm asphalt. If another finishing material is chosen, it is installed according to its specific installation method.

Pros and Cons of Built-Up Roofing (BUR)

Advantages:

Durability. The multilayer structure of bitumen and reinforcing materials reliably protects the roof space from moisture, wind, and other external impacts, including storms.
Waterproofing. Since the membrane is seamless, the risk of water penetration is significantly reduced.
UV protection. The top layer, whether gravel or a special coating, reflects sunlight, slowing the roof’s aging and extending its lifespan. This also reduces air conditioning costs, as the building heats up less in summer.
Strength. BUR systems are so robust that many roofs with this covering retain their performance for decades, sometimes up to 50–100 years.

Now Let’s Look at the Disadvantages of the Technology:

Complex installation. Installation requires the use of hot materials, special equipment, and a well-coordinated professional team. It is not possible to handle this task on your own.
Strong odor. Asphalt fumes often penetrate the building through ventilation, creating significant discomfort. After installation, the building may be uninhabitable for some time.
Hot asphalt application. Liquid bitumen can seep through cracks and seams, causing leaks. In addition, roofers often use propane torches with open flames to secure layers, which increases the risk of fire and injury.
Heavy load on the structure. The multilayer system with gravel is very heavy, and not all buildings can handle such weight. Applying 2–3 plies, weighing several thousand pounds per square, can weaken the structure and cause cracks in walls or façade elements.
Difficult repairs. Damage often goes unnoticed until it affects several layers, and fixing it requires opening the entire system.

If defects can be detected quickly on a smooth surface, leaks on a gravel roof are much harder to notice. As a result, inexperienced contractors often fail to properly fix the problems.

When Built-Up Roofing is a Good Choice

Most flat roofs work well with BUR technology. Thanks to its multilayered design, this type of roofing is highly water-resistant, and its strength makes the surface resistant to wear and even foot traffic. That’s why these roofs are often used as recreational spaces — because even regular movement on the surface won’t compromise their durability.

If hail or a branch punctures the top layer, the lower layers will still hold back water. This is a major advantage of bitumen membranes compared to thermoplastic polyurethane, which has only a single protective layer.

BUR is often used in combination with concrete decks. Its benefit is that fasteners are not required, whereas single-ply systems cannot do without them. This increases the sealing and waterproofing performance of the finished roof.

The technology has been in use for a long time. In fact, many roofs installed right after World War II are still functioning and performing well today.

Roofing & Siding of Cape Cod uses different technologies in roofing installation, including bitumen membranes. We have the expertise, experience, and equipment to perform all work strictly according to standards. We also provide warranties on both materials and installation and conduct regular inspections to detect issues in time.

If you’ve decided to protect your home with a bitumen membrane, contact us for a consultation. We’ll explain all the details of the technology, help calculate the estimate, draw up a contract, and offer convenient project timelines.

Dmitry Labkovich

Since 2002, I have dedicated my career to construction, starting as a cleanup worker and laborer. Despite tough conditions, I quickly mastered roofing and siding, and within six months, I was handling complex tasks. Later, I became a subcontractor, growing the business with a partner and expanding our team.

In 2011, I founded Roofing and Siding of Cape Cod and Boston. At the same time, I continued working with major firms, building a reputation through high-quality work and excellent service. In 2010, I joined the Coast Guard Reserve, which helped me develop leadership skills. Before my deployment in 2018, I built a reliable team that ensured steady company growth.

Today, Roofing and Siding of Cape Cod and Boston is a team of 30+ professionals, all OSHA-certified. We continue to expand while maintaining top-quality standards and exceptional customer service.

**Experience & Expertise**

- 20+ years in the roofing and siding industry
- Hands-on experience from laborer to business owner
- Managing a team of 30+ professionals
- Business development and client relations

**Education & Certification**

- Practical training in roofing and siding techniques
- OSHA safety certification
- Coast Guard Reserve service experience
- Ongoing professional development in construction

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What is Built-Up Roofing