What is Built-Up Roofing (BUR)?
Built-Up Roofing (BUR) is a traditional and durable flat or low-slope roofing system commonly used in commercial and industrial buildings. It consists of multiple layers of reinforcing felt or mats that are alternated with layers of bitumen (asphalt) and surfaced with aggregate, gravel, or a cap sheet.
Components of BUR
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Felts or Mats: BUR typically uses multiple layers of reinforcing materials like fiberglass or organic felts. These layers provide strength and stability to the roofing system.
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Bitumen: Asphalt bitumen serves as the waterproofing agent in BUR. It holds the layers of felts together and provides a waterproof barrier against moisture.
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Surfacing: BUR roofs are commonly surfaced with aggregate (gravel) or a cap sheet. The surfacing protects the bitumen from UV radiation and physical damage while also providing additional fire
Advantages
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Proven Durability: BUR is known for its long lifespan, often lasting 20 years or more with proper maintenance.
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Fire Resistance: The multiple layers and gravel surfacing provide excellent fire resistance.
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Weather Resistance: BUR can withstand various weather conditions and is particularly effective in climates with temperature extremes.
Installation Process
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Preparation: The roof deck is prepared by ensuring it is clean, smooth, and dry. Any necessary repairs or adjustments to the substrate are made before starting the BUR installation.
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Layering: Layers of roofing felt or mats are laid down onto the roof deck. Each layer is mopped or adhered using hot asphalt or cold adhesive.
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Bitumen Application: Hot bitumen is applied over the felts, and a roofing mop or spreader is used to evenly distribute the bitumen across the surface.
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Repeating Layers: The process is repeated with alternating layers of roofing felts and bitumen until the desired number of layers is achieved, typically 3-5 layers.
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Surfacing: Once the layers are complete, the roof surface may be covered with a layer of aggregate (gravel) embedded in hot bitumen or a cap sheet adhered with cold adhesive.
Considerations
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Installation: BUR installation typically requires skilled labor and may involve the use of hot bitumen, which can be hazardous.
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Maintenance: Regular inspection and maintenance are necessary to ensure the longevity of a BUR system, including reapplying surfacing materials as needed.