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IS 1661:1972 is the Indian Standard (BIS) for the application of cement and cement-lime plaster finishes. This code provides comprehensive guidelines for applying cement and cement-lime plaster finishes to walls and ceilings. It details background preparation, mix proportioning, application techniques, and curing to ensure durable, well-bonded, and defect-free finishes.
Code of practice for the application of cement and cement-lime plaster finishes
Overview
Status
Current
Usage level
Frequently Used
Domain
Architectural — Flooring, Wall Finishing and Roofing
! Ensure masonry joints are raked to a depth of 10 mm while the mortar is still green to provide adequate mechanical keying for the plaster.
! Avoid over-troweling the plaster surface with a steel float, as it brings laitance to the surface and causes crazing and shrinkage cracks.
! The background masonry surface must be properly wetted (but not dripping wet) before plastering to prevent it from absorbing water from the plaster mix.
Standard Specification for Application of Portland Cement-Based Plaster
Covers the requirements for the application of portland cement-based plaster (stucco) on various interior and exterior substrates, directly aligning with the core purpose of IS 1661.
BS EN 13914-1:2016BSI / CEN
HighCurrent
Design, preparation and application of external rendering and internal plastering - Part 1: External rendering
This is the primary European standard for external cement plastering (rendering), making it a direct modern counterpart to the external application section of IS 1661.
BS EN 13914-2:2016BSI / CEN
HighCurrent
Design, preparation and application of external rendering and internal plastering - Part 2: Internal plastering
This European standard covers internal plastering, providing modern best practices that correspond to the internal application scope of IS 1661.
BS 5262:1991BSI
MediumWithdrawn
Code of practice for external renderings and internal plastering
As a withdrawn code of practice, it shares a similar prescriptive style with IS 1661 but is now outdated. It represents a historical equivalent from the UK.
Key Differences
≠IS 1661 is a prescriptive standard from 1972 focusing on volumetric site-mixing, while modern standards like ASTM C926 and BS EN 13914 are more performance-oriented, allowing for proprietary pre-blended mixes and advanced admixtures.
≠International standards provide significantly more detailed guidance on movement control joints, detailing for thermal insulation systems, and interaction with a wider variety of modern substrates compared to IS 1661.
≠IS 1661 provides explicit mix proportions for cement-lime plaster, reflecting its common use in India. While lime is permitted in international standards, the emphasis is often on Portland cement plaster modified with chemical admixtures for workability.
≠Modern international standards often include guidance on machine application of plaster, a topic not covered in the original IS 1661.
Key Similarities
≈All standards emphasize the fundamental need for proper surface preparation, including cleaning, roughening, and controlling suction by dampening the substrate before plaster application.
≈The concept of a multi-coat system (e.g., scratch/base coat followed by a finish coat) to build up thickness and achieve a good finish is a common principle across all standards.
≈All standards recognize the critical importance of moist curing for a minimum period to ensure proper cement hydration, minimize shrinkage cracking, and achieve desired strength.
≈The basic constituents of the plaster—Portland cement, properly graded sand, and clean water—are consistent across IS 1661 and its international counterparts.
Parameter Comparison
Parameter
IS Value
International
Source
Nominal Total Plaster Thickness (on masonry)
12 mm to 15 mm
~16 mm (5/8 inch) for two-coat work
ASTM C926
Minimum Curing Period
At least 7 days (moist condition)
48 hours moist cure minimum; must prevent premature drying
ASTM C926
Maximum Aggregate Size (Sand)
Passing 4.75 mm IS Sieve (for undercoats)
Passing No. 4 Sieve (4.75 mm)
ASTM C926 (ref. ASTM C897)
Finish Coat Thickness
2 to 3 mm
~3 mm (1/8 inch)
ASTM C926
Maximum Thickness Per Coat (Undercoat)
10-15 mm (not strictly defined)
10 mm (3/8 inch)
ASTM C926
Interval Between Coats
Undercoat to be 'sufficiently hard'
24 to 48 hours is typical to allow for sufficient rigidity
ASTM C926
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
single coat plaster thickness12 mm
under coat thickness two coat work10 to 12 mm
finishing coat thickness two coat work3 to 8 mm
minimum curing period7 days
wait time between coatsat least 2 days
Tables & Referenced Sections
Key Tables
Table 1 - Recommended Mix Proportions for Cement and Cement-Lime Plasters
Table 2 - Number of Coats and Thickness of Plaster for Different Backgrounds