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IS 1609:1991 is the Indian Standard (BIS) for laying damp-proofing treatment using bitumen felts. This code specifies the standard procedures and requirements for executing damp-proofing treatments (DPC) in buildings using bitumen felts. It covers surface preparation, application of primer, laying and bonding techniques, and specific requirements for overlaps to prevent capillary moisture ingress.
Code of practice for laying damp-proofing treatment using bitumen felts
! Ensure the concrete or masonry base is completely dry, clean, and free of dust before applying the bitumen primer to prevent debonding.
! Trapped moisture during the laying process can cause blistering; laying should be avoided during rainy or highly humid conditions.
! For rough masonry surfaces, a leveling coat of cement mortar (1:3 or 1:4, min 12 mm thick) must be applied, troweled smooth, and cured before commencing damp-proofing.
BS 8215:1991BSI (British Standards Institution), UK
HighWithdrawn
Code of practice for design and installation of damp-proof courses in masonry construction
Provides guidance on laying damp-proof courses, sharing a very similar prescriptive approach to IS 1609.
BS 8102:2022BSI (British Standards Institution), UK
MediumCurrent
Protection of below ground structures against water from the ground. Code of practice
Modern UK equivalent covering all below-ground waterproofing, where bitumen sheets (Type A) are one option.
ASTM D6769 − 02(2021)ASTM International, USA
MediumCurrent
Standard Guide for Application of Fully Adhered Hot-Applied Reinforced Waterproofing Systems
Covers the application of hot-applied bitumen systems, but is a 'guide' and often involves reinforced liquid systems.
Key Differences
≠IS 1609 is a prescriptive standard detailing specific methods and dimensions, whereas modern equivalents like BS 8102:2022 are performance-based, requiring designers to achieve a certain 'Grade' of protection based on risk assessment.
≠BS 8102:2022 introduces a comprehensive waterproofing design philosophy using Types A (barrier), B (integral structure), and C (drained cavity), a framework not present in the more straightforward approach of IS 1609.
≠IS 1609 explicitly refers to older Indian bitumen grades (e.g., 85/25, 90/15), while international standards reference materials compliant with their own regional specifications (e.g., ASTM or EN standards), which often include polymer-modified bitumens.
≠IS 1609 provides a single set of guidelines, whereas BS 8102 requires the appointment of a 'waterproofing specialist' as part of the design team for more complex projects.
Key Similarities
≈All standards universally emphasize the critical need for the substrate to be clean, dry, smooth, and free of contaminants before applying the primer and felt.
≈The fundamental principle of ensuring continuity of the damp-proofing system is central to all codes, stressing the importance of correct lapping, sealing, and detailing around corners and penetrations.
≈The use of a bitumen primer to promote adhesion between the substrate and the bitumen felt is a common requirement across IS 1609 and its international counterparts.
≈All standards specify the need for a protective layer (e.g., screed, backfill, or protection board) to be placed over the finished membrane to prevent mechanical damage during subsequent construction activities.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Side Lap Width
75 mm
75 mm (for torch-on and bonded felts)
BS 8215:1991
Minimum End Lap Width
100 mm
100 mm (for torch-on and bonded felts)
BS 8215:1991
Design Approach
Prescriptive code of practice
Performance-based risk assessment (Grades 1-3)
BS 8102:2022
Bonding Material
Hot bitumen of suitable grade (e.g., 85/25)
Hot-applied rubberized asphalt or as per system manufacturer's specification
ASTM D6769 − 02(2021)
Primer Application Rate
0.25 to 0.50 litres/m²
Typically 0.3 - 0.4 litres/m² (1 gal/100-150 ft²), based on manufacturer guidance
ASTM D6769 − 02(2021)
Protection of Membrane
A course of sand blinding or protective layer of cement mortar (1:4) or concrete.
A compatible protection board, drainage composite, or screed should be installed to prevent damage.
BS 8102:2022
Number of Coats for Tanking (Basements)
Minimum 3 coats for heads up to 3m; 5 coats for heads from 3m to 6m.
Number of layers determined by the system design to meet the required Performance Grade (1, 2, or 3).
BS 8102:2022
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Side lap for bitumen felt75 mm (min)
End lap for bitumen felt100 mm (min)
Bitumen primer application rate0.27 to 0.32 litres/sq.m
Hot bitumen bonding application rate1.2 kg/sq.m per coat
Levelling mortar thickness for rough surfaces12 mm (min)
What is the minimum overlap required when joining bitumen felts?+
A minimum overlap of 75 mm is required for longitudinal (side) laps and 100 mm for transverse (end) laps.
What type of bitumen is used for bonding the felts?+
Industrial blown type bitumen conforming to IS 702, typically applied hot at a rate of 1.2 kg/m².
Is a primer necessary before laying the bitumen felt?+
Yes, a cold applied bitumen primer conforming to IS 3384 must be applied to the completely dry base surface to ensure proper adhesion of the hot bitumen.