Built-Up Roofing in Construction in Canada: A Complete Guide

When it comes to construction in Canada, particularly in the commercial and industrial sectors, built-up roofing (BUR) has proven itself as a reliable and durable option for flat and low-sloped roofs. This roofing system, often referred to as tar and gravel roofing, is a time-tested solution that has been widely adopted in both residential and commercial projects across the country. Understanding its components, installation process, advantages, and maintenance needs is crucial for any builder, contractor, or property owner considering this option.

What is Built-Up Roofing (BUR)?

Built-up roofing (BUR) is a roofing system that consists of multiple layers of bitumen (asphalt or coal tar) alternated with reinforcing fabrics. The layers of BUR are built up over time, creating a strong, water-resistant barrier. Typically, the system features three to five layers of these materials, which are then topped with gravel or a similar aggregate. This multi-layered system provides significant protection against weather elements and offers impressive durability for buildings located in Canada’s diverse climates.

BUR is often installed on flat roofs or low-slope roofs, which are commonly found in commercial buildings, industrial structures, and multi-family residential units in cities such as Toronto, Vancouver, and Montreal.

Components of Built-Up Roofing

The key components that make up a built-up roofing system include:

• Base Sheet: This is the initial layer of the roofing system, which provides a stable foundation for the subsequent layers.
• Bitumen: Bitumen is the primary material used in BUR systems. It can be asphalt or coal tar and serves as the waterproofing agent.
• Reinforcing Fabrics: These are layers of materials such as fiberglass or polyester mats that are embedded between the layers of bitumen to add strength and durability to the roof system.
• Surfacing: The top layer of the roof, often covered with gravel, stone, or other aggregates, serves to protect the underlying layers from UV radiation and weather elements.

Advantages of Built-Up Roofing in Canada

1. Durability and Longevity

One of the main reasons why built-up roofing systems are preferred in construction in Canada is their exceptional durability. BUR systems are known to last for several decades, with many installations lasting 30 years or more with proper maintenance. This makes them a cost-effective choice for building owners in Canada who are looking for a long-term roofing solution.

Given the country’s harsh winters, heavy snowfall, and extreme temperature fluctuations, the durability of BUR systems is a significant benefit. The multiple layers of bitumen provide excellent resistance to these elements, ensuring that the roof remains intact and functional even in the face of severe weather conditions.

2. Weather Resistance

Canada’s diverse climates—from the coastal rain of Vancouver to the freezing temperatures of Edmonton—pose unique challenges to roofing systems. Built-up roofing excels in protecting buildings from these climatic extremes. The layers of asphalt or coal tar used in BUR systems create an excellent water barrier, which helps prevent leaks and water damage from rain, snow, and ice. Additionally, the gravel surface helps to deflect UV rays, reducing the risk of thermal damage and keeping the roof cool during the hot summer months.

3. Energy Efficiency

Built-up roofing systems can significantly improve the energy efficiency of a building. The reflective properties of the gravel or stone surface help to reduce heat absorption, thus lowering the energy required to cool the building during warmer months. This is particularly important in Canada’s southern regions, such as Ontario and Quebec, where temperature extremes in both summer and winter can drive up energy costs. By installing a BUR system, building owners can reduce their reliance on air conditioning and heating, resulting in lower energy bills over time.

4. Low Maintenance Requirements

Once installed, built-up roofing systems are relatively easy to maintain. The strong, layered construction of BUR provides a protective shield against many of the issues that affect traditional roofing systems, such as leaks, cracks, and wear from weather exposure. Routine inspections and minor repairs, such as replenishing gravel or replacing worn-out areas, can help extend the lifespan of the roof.

In Canada, where roofs are subjected to snow accumulation and ice dams, regular maintenance of built-up roofs can ensure that these structures remain in top condition for years. Additionally, BUR systems are resistant to moss, algae, and fungus growth, which can be problematic for other roofing systems.

The Installation Process of Built-Up Roofing in Canada

The installation of a built-up roofing system requires significant expertise, as it involves several layers of materials that must be carefully applied to create a durable, waterproof surface. The process typically involves the following steps:

1. Surface Preparation

Before any materials are applied, the roof surface must be thoroughly prepared. This includes cleaning the roof deck, removing any debris, and ensuring that the surface is smooth and dry. The roof deck is typically made of plywood, OSB, or concrete.

2. Applying the Base Sheet

The base sheet is the first layer of the BUR system. This sheet is typically made of fiberglass or polyester and is adhered to the roof deck using a layer of bitumen. The base sheet helps to create a stable foundation for the subsequent layers.

3. Layering Bitumen and Reinforcing Fabrics

Next, bitumen is applied in layers, followed by a layer of reinforcing fabric. The bitumen is typically heated before being spread over the surface, allowing it to bond with the fabric and create a seamless, waterproof barrier. This process is repeated several times, with each layer of fabric adding strength and durability to the system.

4. Final Surfacing

The final step in the installation process is to apply the surfacing material, which is typically gravel or stone. This layer serves multiple purposes, including providing protection from UV rays, adding weight to prevent wind uplift, and improving the roof’s overall aesthetic. In some cases, an alternative surfacing material, such as a cool roof coating, may be applied for enhanced energy efficiency.

Built-Up Roofing Maintenance in Canada

While BUR systems are known for their low maintenance requirements, regular inspection and upkeep are still necessary to ensure their long-term performance. Here are some key maintenance tips for BUR systems in Canada:

• Regular Inspections: Periodic inspections should be conducted to identify any wear or damage, particularly after severe weather events. Inspectors should check for cracks, blisters, and any areas where the bitumen may have worn thin.
• Clear Debris: It’s important to keep the roof free of debris, leaves, and branches, which can block drainage systems and cause water to pool on the roof.
• Replenish Gravel: Over time, the gravel surfacing may erode or shift. It’s important to replenish the gravel to maintain the roof’s protective qualities.

Conclusion

Built-up roofing (BUR) remains one of the most trusted and durable roofing systems for construction in Canada. Offering unmatched weather resistance, durability, and energy efficiency, BUR is a preferred choice for commercial, industrial, and residential properties alike. Its multi-layered construction, long lifespan, and low maintenance requirements make it an ideal solution for buildings in Canada’s harsh climate.

For anyone considering a BUR system for their construction project in Canada, it’s essential to work with a qualified roofing contractor who understands the intricacies of the installation process. With the right care and maintenance, a built-up roof can protect a building for decades, offering both performance and value.

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