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IS 3620:1979 is the Indian Standard (BIS) for laterite stone block for masonry. This standard specifies the requirements for laterite stone blocks used in masonry construction, covering standard dimensions, tolerances, dressing standards, and physical properties to ensure suitability for structural and architectural applications.
! Laterite stones are soft when freshly quarried containing natural moisture but harden significantly upon prolonged exposure to air; they should be cut and dressed early.
! Due to the porous nature of laterite, exterior walls built with these blocks in high-rainfall regions often require protective pointing or plastering to prevent moisture ingress.
! Ensure blocks are free from cracks, flaws, and significant voids before structural use.
Specification for masonry units - Part 6: Natural stone masonry units
Specifies requirements for masonry units made from quarried natural stone, covering the same functional purpose.
ASTM C568 / C568M - 15ASTM International, USA
MediumCurrent
Standard Specification for Limestone Dimension Stone
Covers a specific type of natural stone (limestone) for building, with similar parameter requirements.
NZS 4298:1998Standards New Zealand, New Zealand
MediumCurrent
Materials and workmanship for earth buildings
Covers unfired earth blocks (adobe), which are materially similar to some forms of laterite.
ASTM C90-18ASTM International, USA
LowCurrent
Standard Specification for Loadbearing Concrete Masonry Units
Provides a benchmark for a common load-bearing masonry unit, though the material is different.
Key Differences
≠IS 3620 is prescriptive, setting a minimum compressive strength (1.5 N/mm²). In contrast, BS EN 771-6 is performance-based, requiring manufacturers to declare the strength without setting a universal minimum.
≠The minimum strength required by IS 3620 (1.5 N/mm²) is significantly lower than for mainstream materials like concrete blocks under ASTM C90 (approx. 13.8 N/mm²), reflecting laterite's nature as a soft stone.
≠IS 3620 is specific to laterite, a regional material. International standards tend to be either for a broad category (e.g., all natural stone in EN 771-6) or for globally traded materials (e.g., limestone in ASTM C568).
≠Modern standards like EN 771-6 include durability requirements such as freeze-thaw resistance. IS 3620 does not, which is consistent with the tropical climates where laterite is traditionally used.
Key Similarities
≈Both IS 3620 and its counterparts aim to define minimum quality and performance characteristics for masonry units to ensure they are fit for purpose in construction.
≈Key physical properties such as compressive strength, water absorption, and dimensional tolerances are identified as critical parameters across all compared standards.
≈All standards specify the basic methodology for sampling and testing, such as testing a set number of units to determine average properties.
≈IS 3620's requirement for blocks to be 'free from veins, cracks, and other defects' is conceptually parallel to clauses on material structure and appearance in standards like BS EN 771-6.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Average Compressive Strength
1.5 N/mm²
No minimum specified; manufacturer declares the value.
BS EN 771-6:2011+A1:2015
Minimum Average Compressive Strength (Functional Comparison)
1.5 N/mm² (for laterite stone)
13.8 N/mm² (2000 psi) (for concrete block)
ASTM C90-18
Maximum Water Absorption
20% by mass
No maximum specified; manufacturer declares the value.
BS EN 771-6:2011+A1:2015
Dimensional Tolerance (on length/width)
± 5 mm
± 3.2 mm (± 1/8 in)
ASTM C90-18
Dimensional Tolerance Classes
A single tolerance value is specified.
Manufacturer declares a tolerance class (e.g., T1, T2, T3, T4).
BS EN 771-6:2011+A1:2015
Durability Requirement
Not specified (implicitly for non-freezing climates)
Freeze-thaw resistance declaration required where relevant.
BS EN 771-6:2011+A1:2015
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Standard lengths300, 400, 500, 600 mm
Standard widths150, 200, 250 mm
Standard heights150, 200, 250, 300 mm
Dimensional tolerance±5 mm
Minimum compressive strength35 kg/cm² (approx 3.5 N/mm²) typical for structural use
Tables & Referenced Sections
Key Tables
Table 1 - Standard Dimensions of Laterite Stone Blocks
What is the permissible tolerance in the dimensions of laterite blocks?+
The standard allows a dimensional tolerance of ±5 mm.
How is the water absorption of laterite blocks tested?+
Water absorption and specific gravity are tested in accordance with the procedures laid out in IS 1124.
Are laterite blocks suitable for high-rise buildings?+
No, due to their relatively lower compressive strength compared to concrete or granite, they are strictly recommended for low-rise or light-to-medium load-bearing structures.