What are the common thicknesses for APP membranes?

Commonly available in 2mm, 3mm, and 4mm. The minimum thickness required depends on the type and class as specified in Table 1.

What is the minimum required tensile strength for a polyester reinforced membrane?

For Type 2 (polyester reinforced), the minimum longitudinal tensile strength is 650 N/50mm as per Table 1.

What does the cold flexibility test signify?

It indicates the lowest temperature at which the membrane can be bent without cracking. For Type 2 sheets, it is -5 °C (Table 1), making it crucial for regions with cold winters.

Is this standard still active?

No, IS 15808:2008 has been superseded by the revised version, IS 15808:2019.

IS 15808

: 2008

Polymer modified bituminous sheets for waterproofing - Specification

CurrentFrequently UsedSpecificationBIMMaterials Science · Waterproofing and Damp Proofing

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This standard specifies the requirements for polymer-modified bituminous sheets used for waterproofing applications. It covers the material composition, dimensions, physical and mechanical properties for different types of sheets, such as those reinforced with polyester or glass fibre, intended for applications like roofing and tanking.

Specifies requirements for polymer modified bituminous sheets, such as APP or SBS modified membranes, used for waterproofing.

Quick Reference Values

Minimum Thickness (Type 2, Class B)3.0 mm

Tensile Strength Longitudinal (Polyester Reinforced)≥ 650 N/50 mm

Elongation at Break (Polyester Reinforced)≥ 40 %

Cold Flexibility (Type 2)No crack at -5 °C

Water Absorption (Max)1 % by mass

Softening Point of the compound≥ 150 °C

Practical Notes

The choice between APP (Atactic Polypropylene) and SBS (Styrene Butadiene Styrene) modified membranes is critical; APP offers better UV/heat resistance, while SBS provides superior low-temperature flexibility.

Reinforcement type significantly impacts performance. Polyester reinforcement offers high elongation and puncture resistance, ideal for roofs with movement. Glass fibre provides excellent dimensional stability but lower elongation.

Proper application technique (e.g., torching, surface preparation, overlaps) is as crucial as the material quality for achieving a leak-proof waterproofing system.