What are the main types of bitumen felts as per this standard?

Type 1 (Underlay), Type 2 (Self-finishing), and Type 3 (Hessian-based) are the three main types, each with different grades (Clause 3).

What is the key difference between Grade 1 and Grade 2 felts?

Grade 2 felts have superior physical properties, such as higher breaking strength and better heat resistance, making them suitable for more demanding applications compared to Grade 1 (Table 1).

What is the minimum breaking strength for a standard hessian-based felt (Type 3, Grade 1)?

The minimum longitudinal breaking strength is 350 N per 50 mm width, and transverse strength is 200 N per 50 mm width (Table 1).

How should bitumen felt rolls be stored on site?

Rolls should be stored upright on a clean, level surface, away from direct sunlight and heat, and protected from physical damage (Clause 11).

IS 1322

: 1982

Bitumen felts for waterproofing and damp-proofing - Specification

CurrentFrequently UsedSpecificationBIMMaterials Science · Waterproofing and Damp Proofing

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This standard specifies the requirements for bitumen felts intended for use in waterproofing and damp-proofing of buildings. It covers the classification, materials, manufacture, dimensions, physical properties, and testing methods for different types and grades of bitumen felts.

Specifies requirements for bitumen felts used as waterproofing and damp-proofing barriers in buildings.

Quick Reference Values

Min. longitudinal breaking strength for Type 3 Grade 1 felt350 N / 50 mm width

Min. transverse breaking strength for Type 3 Grade 1 felt200 N / 50 mm width

Pliability test mandrel diameter for Type 3 Grade 1 felt20 mm

Max. water absorption for Type 3 felts1.0 % by mass

Heat resistance test temperature for Type 3 Grade 170 °C

Nominal roll width1 m

Nominal roll length10 m or 20 m

Practical Notes

Ensure the surface is clean, dry, and primed with an appropriate bitumen primer before laying the felt.

Proper overlapping (typically 75-100 mm for side laps and 150 mm for end laps) and sealing of joints is critical for an effective waterproofing system.

Type 3 (hessian-based) is commonly used for general waterproofing, while Type 2 (fibre-based, self-finishing) is often used for exposed roofing applications.