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IS 1640:1960 is the Indian Standard (BIS) for waterproofing of roofs with bitumen felts. This code specifies the procedures and practices for waterproofing roofs using bitumen felts. It details the requirements for surface preparation, primer application, bonding bitumen application, felt overlapping, and the handling of critical roof details such as parapets, drains, and gutters.
Lays down the code of practice for waterproofing of roofs using bitumen felts.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Ensure the roof surface is bone dry and thoroughly cleaned of dust and debris before applying the bitumen primer to prevent blistering and poor adhesion.
! Stagger the joints of consecutive layers of felt in multi-layer treatments to avoid creating continuous weak spots.
! Pay special attention to flashing details at parapet walls and roof penetrations, as these are the most common failure points for leaks.
BS 8217:2005BSI - British Standards Institution, UK
HighCurrent
Reinforced bitumen membranes for roofing. Code of practice
Provides guidance on the design and application of reinforced bituminous roofing, covering similar principles of multi-layer systems.
DIN 18531-3:2017-07DIN - Deutsches Institut für Normung, Germany
HighCurrent
Waterproofing of roofs and of decks and balconies - Part 3: Selection, design principles and details
Covers the execution and detailing of roof waterproofing systems, including those using bitumen sheets.
NRCA Roofing Manual: Membrane Roof Systems - 2023NRCA - National Roofing Contractors Association, USA
MediumCurrent
The NRCA Roofing Manual: Membrane Roof Systems
A comprehensive industry guide rather than a standard, but its chapter on built-up roofing (BUR) details equivalent application practices.
ASTM D226 / D226M - 18ASTM International, USA
LowCurrent
Standard Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing
This is a material specification for the felt itself, a component used within the system described by IS 1640, not an application code.
Key Differences
≠Material Technology: IS 1640 is based on traditional organic (hessian/fibre) felts, whereas modern international standards (e.g., BS 8217) focus on polymer-modified bitumen (SBS, APP) with superior polyester or glass fibre reinforcement for enhanced flexibility and durability.
≠Application Methods: IS 1640 primarily details the 'pour and roll' method with hot-mopped bitumen. Modern codes also extensively cover torch-on application and self-adhesive membranes, which offer faster installation and different performance characteristics.
≠System Integration: Modern standards like BS 8217 and DIN 18531 integrate waterproofing with thermal insulation (warm/inverted roofs) and vapour control layers as part of a complete roof system design, concepts not addressed in IS 1640:1960.
≠Health and Safety: International standards have significantly more detailed and stringent requirements for worker health and safety, including fume control for hot bitumen, fire prevention protocols for torch-on work, and general site safety, which are minimal in the 1960 code.
Key Similarities
≈Fundamental Principle: All standards are based on the core concept of creating a continuous, multi-layer waterproof membrane by bonding successive layers of bitumen-impregnated felt together with bitumen.
≈Emphasis on Surface Preparation: Both IS 1640 and its international counterparts stress the critical importance of having a clean, dry, smooth, and properly graded substrate to ensure full adhesion and effective drainage.
≈Lapping Technique: The method of overlapping adjacent sheets of felt (side and end laps) to prevent water ingress at joints is a fundamental and common requirement across all the standards.
≈Detailing at Terminations: All codes recognize that upstands, parapets, and penetrations are high-risk areas and provide specific guidance on how to carry the waterproofing membrane up vertically to ensure continuity and prevent failure.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Side Lap Width
75 mm
75 mm (for pour and roll method)
BS 8217:2005
Minimum End Lap Width
100 mm
100 mm (for pour and roll method)
BS 8217:2005
Minimum Upstand Height
150 mm
150 mm above finished roof level
BS 8217:2005
Felt Reinforcement Type
Hessian (jute) or fibre base
Polyester or glass fibre
BS 8217:2005
Bitumen Application Temperature (Typical)
180°C - 200°C (for 85/25 grade)
Working temperature should not exceed manufacturer limits, often around 210°C - 230°C
BS 8217:2005
Surface Protection
Gravel or coarse sand embedded in a final bitumen coat.
Mineral granules (factory applied), stone chippings, paving slabs, or ballast.
BS 8217:2005
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Bitumen application rate for bonding1.2 kg/sqm
Bitumen primer application rate0.27 to 0.40 kg/sqm