Built-Up Roof (BUR) in Construction: A Comprehensive Guide for the USA

Built-Up Roofs (BUR) have been a staple in the roofing industry for decades. This multi-layered roofing system is widely known for its durability, versatility, and cost-effectiveness, making it a popular choice in construction across the USA. In this article, we will delve deep into the built-up roofing system, covering its components, benefits, installation process, maintenance, and how it compares to other roofing options.

What is a Built-Up Roof?

A Built-Up Roof (BUR) is a traditional roofing system constructed by layering multiple layers of roofing felt, bitumen, or asphalt. These layers are applied over a prepared base to create a waterproof and highly durable barrier. The typical BUR system consists of alternating layers of felt and asphalt or bitumen, making it a reliable and long-lasting option for low-slope roofs. Often topped with a layer of gravel or mineral granules, these roofs offer excellent protection from environmental factors such as rain, UV rays, and wind.

Components of a Built-Up Roof

The built-up roofing system is composed of several key components that work together to provide a weather-resistant, long-lasting roofing solution.

1. Roofing Felt

Roofing felt serves as the foundation of the BUR system. It is typically made from fiberglass or organic materials and is treated with asphalt or bitumen to enhance its waterproofing properties. The felt is rolled out and applied in layers to provide structural strength and protection against leaks.

2. Bitumen or Asphalt

Bitumen or asphalt is used to bond the layers of roofing felt together. It acts as a waterproofing agent that seals the roof, preventing water from penetrating the structure. The bitumen is applied hot or cold, depending on the specific system and installation method chosen.

3. Additional Layers

The number of layers in a BUR system can vary depending on the desired level of protection. In general, the more layers applied, the more durable and resistant the roof will be. Some systems include up to five or more layers of roofing felt and bitumen.

4. Gravel or Mineral Granules

To protect the roofing system from UV rays and physical damage, the final layer of a BUR roof is often covered with gravel, mineral granules, or reflective coatings. This layer not only provides additional protection but also helps with heat resistance, making BUR roofs a great option for energy efficiency.

Advantages of Built-Up Roofing in Construction

1. Durability and Longevity

One of the primary benefits of a Built-Up Roof is its impressive durability. Due to its multi-layer construction, BUR roofs are highly resistant to wear and tear, especially in areas with extreme weather conditions. With proper maintenance, a well-installed BUR roof can last 20 to 30 years or more, making it a wise investment for building owners.

2. Superior Waterproofing

The bitumen and felt layers in a built-up roofing system create a seamless barrier against water infiltration. This waterproofing ability makes BUR roofs an excellent choice for buildings in areas that experience heavy rainfall or snowfall. The system is designed to withstand ponding water, a common issue with low-slope roofs.

3. Low Maintenance Requirements

BUR systems are relatively low-maintenance compared to other roofing materials. While routine inspections and cleaning are recommended, the multi-layer design minimizes the risk of leaks and damage. The durability of the system reduces the need for frequent repairs, which ultimately saves on long-term costs.

4. Fire Resistance

Built-Up Roofs provide excellent fire resistance due to their layered structure and the fire-resistant properties of asphalt. This makes BUR roofs ideal for buildings that require a high level of fire protection, such as commercial and industrial properties.

5. Energy Efficiency

A BUR system can improve a building’s energy efficiency. The reflective gravel or mineral granules used in the final layer of the roof help to reflect sunlight, reducing the amount of heat absorbed into the building. This can lower cooling costs in the summer months and enhance the overall comfort of the building.

Installation Process of Built-Up Roofs

Installing a Built-Up Roof involves several steps that must be performed by skilled professionals to ensure a high-quality result.

1. Surface Preparation

Before installing the BUR system, the roof’s surface must be thoroughly cleaned and prepared. This involves removing any debris, old roofing materials, or contaminants that could affect the adhesion of the roofing layers.

2. Layering Felt and Bitumen

Once the surface is prepared, roofing felt is rolled out and secured to the roof deck. Bitumen or asphalt is then applied over the felt, bonding the layers together. This process is repeated for each additional layer of felt, ensuring that each layer is properly sealed.

3. Application of the Top Layer

After the desired number of felt layers have been applied, a final layer of bitumen is spread across the surface. The final layer is then covered with gravel, mineral granules, or a reflective coating to provide additional protection from the elements.

4. Curing and Inspection

Once the roof layers are in place, the bitumen needs time to cure and set. This curing process ensures that the roof is fully waterproof and secure. After curing, the roofing system is inspected for any defects or areas that need additional attention.

Maintenance of Built-Up Roofs

Though BUR roofs are low-maintenance, periodic inspection and care are essential to ensure the roof’s longevity. Some common maintenance tasks include:

• Regular Inspections: Inspect the roof annually and after severe weather events to identify any damage or wear.
• Cleaning: Remove debris, leaves, or branches that can accumulate on the roof and impede drainage.
• Repairs: Address any cracks, blisters, or punctures promptly to prevent leaks.
• Re-coating: After several years, the reflective gravel or granules may need to be replenished to maintain the roof’s energy efficiency and UV protection.

Comparing Built-Up Roofs to Other Roofing Systems

While Built-Up Roofs offer numerous benefits, it’s important to consider how they compare to other roofing options, such as:

1. Modified Bitumen Roofing

Modified bitumen roofing is similar to BUR but utilizes pre-manufactured rolls with a modified bitumen layer. It is easier and faster to install but may not offer the same level of long-term durability and customization as a traditional BUR system.

2. Single-Ply Membranes (TPO, PVC, EPDM)

Single-ply membranes like TPO, PVC, and EPDM are lightweight and easier to install than BUR systems. However, they typically offer less durability, and their resistance to punctures and extreme weather conditions is lower compared to BUR systems.

3. Metal Roofing

Metal roofing is another popular choice for low-slope roofs, known for its strength and longevity. However, metal roofing systems can be more expensive than BUR and may require additional insulation for energy efficiency.

Conclusion

Built-Up Roofs (BUR) remain one of the most reliable, durable, and cost-effective roofing solutions in the USA. Their multi-layer construction offers unparalleled protection against weather elements, while their fire resistance, low maintenance, and energy efficiency make them a preferred choice for commercial and industrial buildings. With proper installation and routine maintenance, BUR roofs can provide decades of service, ensuring long-term protection for your building.

For more information on this roofing solution, visit this article.