BITUMEN WASHER

Product Specification :

Bitumen Washers (often referred to as felt or fiber washers) are heavy-duty sealing components made from high-quality fibers impregnated with bitumen (asphalt). They are the traditional choice for waterproofing fasteners in heavy industrial roofing, particularly when used with corrugated asbestos-cement or fiber-cement sheeting.

1. Functional Design
Bitumen washers are designed to be "self-healing." When the fastener is tightened, the bitumen is slightly squeezed, creating a viscous, waterproof plug that seals both the hole in the roofing sheet and the area around the bolt or screw shank.
Shape: Usually flat or slightly domed.
Texture: Fiber-reinforced, slightly tacky to the touch.
Deformation: Unlike rubber, bitumen washers conform permanently to the irregular surface of corrugated sheets.

2. Material Specifications
Feature    Specification
Base Material    Organic or synthetic fibers (cellulose or felt).
Impregnant    Refined Bitumen / Polymer-modified Asphalt.
Temperature Range    Stable from -10°C to +80°C.
Chemical Resistance    Resistant to salt air, dilute acids, and alkalis common in industrial areas.

3. Key Technical Features
Compatibility: Specifically designed for use with fiber-cement and bituminous corrugated sheets. They are often used in conjunction with a plastic or metal "caps" to provide a secondary layer of UV protection.
Self-Sealing: The bitumen "flows" into micro-cracks around the drill hole, ensuring a long-term seal even as the building vibrates or the sheets shift.
Thickness: Usually thicker than standard EPDM washers (typically 2mm to 4mm) to provide better cushioning for brittle roofing materials.

4. Dimensional Standards
Bitumen washers are sized by their outer diameter (OD) and the internal diameter (ID) of the hole.
Size (OD)    Hole (ID)    Typical Fastener
25mm    6mm - 8mm    M6 Hook Bolts / Drive Screws
32mm    8mm - 10mm    Heavy-duty M8 Roofing Bolts

5. Installation Performance
Because bitumen is a thermoplastic material, its performance is affected by temperature:
In Cold Weather: The washers can become brittle. It is recommended to keep them at room temperature before installation to ensure they remain pliable enough to seal.
In Hot Weather: The bitumen softens, which improves the seal but can result in "bleeding" (excess bitumen squeezing out). This is normal and actually indicates a successful seal.
Compression: They should be tightened until the washer is firmly compressed, but not so tight that the fiber-cement roofing sheet cracks.

6. Primary Applications
Agricultural Buildings: Securing fiber-cement roofs on barns and sheds.
Industrial Warehousing: Used with heavy-duty hook bolts on steel purlins.
Repair & Maintenance: Replacing old, perished seals on traditional corrugated roofs.