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IS 6408:2000 (Part 2) is the Indian Standard (BIS) for recommendations for modular coordination in the building industry: tolerances, part 2: principles and applications. This standard provides recommendations and guiding principles for setting and applying dimensional tolerances in the building industry, specifically within a modular coordination framework. It covers the concepts of manufacturing, erection, and induced tolerances, and how to calculate them to ensure proper fit and assembly of components, especially in prefabricated construction. This document is Part 2, focusing on principles and applications.
Recommendations for modular coordination in the building industry: Tolerances, Part 2: Principles and applications
Overview
Status
Current
Usage level
Specialized
Domain
Architectural — Planning, Housing and Pre-fabricated Construction
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! The core principle is to design on a 'planning grid' based on the 100mm module (M), which governs the placement of structural elements and components.
! A clear distinction must be made between 'grid dimensions' (controlling dimensions) and 'component work sizes', with the difference accommodating joints and tolerances.
! Effective implementation requires adoption from the very beginning of the conceptual design phase and consistent application across all project disciplines (Architectural, Structural, MEP).
ISO 1803:2023ISO (International Organization for Standardization)
HighCurrent
Buildings and civil engineering works — Vocabulary for tolerances and accuracy
Provides the most up-to-date international vocabulary for building tolerances, directly aligning with the IS code's subject matter.
ISO 1803:1997ISO (International Organization for Standardization)
HighWithdrawn
Building construction — Tolerances — Vocabulary
This was the likely basis for IS 6408:2000, sharing an almost identical scope and conceptual framework.
ISO 6707-1:2020ISO (International Organization for Standardization)
MediumCurrent
Buildings and civil engineering works — Vocabulary — Part 1: General terms
A broader vocabulary standard that includes a section on tolerances and measurement, overlapping with key terms in the IS code.
BS 6954-1:1988BSI (British Standards Institution), United Kingdom
MediumWithdrawn
Tolerances for building. Recommendations for basic principles for aiming for fit
A historical UK standard whose glossary section covered the same fundamental concepts of tolerance, deviation, and fit.
Key Differences
≠IS 6408:2000 is based on concepts from the late 1990s (like ISO 1803:1997), while current international standards like ISO 1803:2023 have been updated to reflect modern surveying techniques and statistical concepts of accuracy.
≠The Indian standard is part of a series specific to 'Recommendations for Modular Co-ordination', whereas the ISO equivalents are more general vocabulary standards for all types of building tolerances and accuracy, not just modular.
≠Modern ISO standards may introduce terms related to digital construction (BIM) and data-driven accuracy control, which are absent in the 20-year-old IS code.
≠The scope of the current ISO 1803:2023 explicitly includes 'civil engineering works' alongside 'buildings', making it broader than the IS code which is focused on the 'Building Industry'.
Key Similarities
≈Both the IS code and its international equivalents are fundamentally glossaries, established to create a common, unambiguous language for designers, manufacturers, and contractors regarding tolerances.
≈The core concepts defined, such as 'tolerance', 'deviation', 'basic size', 'actual size', and 'limits of size', form the foundation of both the Indian and international frameworks.
≈All standards utilize the concept of a 'basic size' as a theoretical reference from which permissible deviations and tolerances are calculated.
≈The hierarchical structure of tolerances (e.g., distinguishing between manufacturing, setting-out, and erection tolerances) is a shared principle, even if the specific terms vary slightly.
Parameter Comparison
Parameter
IS Value
International
Source
Tolerance
The difference between the upper and lower limits of size.
Difference between the upper limit of size and the lower limit of size.
ISO 1803:2023
Deviation
The algebraical difference between a size (actual, limit, etc) and the corresponding basic size.
Difference between a size and the corresponding basic size.
ISO 1803:2023
Basic Size
The size by reference to which the limits of size are fixed. It is a theoretically exact size.
Size by reference to which the limits of size are fixed.
ISO 1803:2023
Actual Size
The size of a component as measured. It is the value of a physical measurement.
Size of a feature obtained by measurement.
ISO 1803:2023
Clearance
The difference between the sizes of two components which are to be assembled.
Difference between the sizes of two features before assembly, where this difference is positive.
ISO 1803:2023
Inaccuracy
The total deviation from the specified value which includes errors resulting from measurement, setting-out and erection.
Difference between the mean of a set of measured values and a reference value (true or accepted).
ISO 1803:2023
Permissible Deviation
The deviation permitted by the specification for the work. It is numerically equal to the tolerance.
Extreme value for a deviation permitted by the specification for the work.
ISO 1803:2023
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Basic Module (M)100 mm
Recommended Horizontal Multi-module3M (300 mm)
Secondary Horizontal Multi-module6M (600 mm)
Recommended Vertical Multi-module1M (100 mm)
Typical Joint Thickness Range0 to 20 mm
Key Formulas
J = T + C — Basic formula for Joint Width (J) relating Total Tolerance (T) and Clearance (C)
T = sqrt(T1^2 + T2^2 + ... + Tn^2) — Statistical summation of independent tolerances
Tables & Referenced Sections
Key Tables
Table 1 - Examples of Components and Their Relevant Tolerances
Key Clauses
Clause 3 - Terminology
Clause 4 - Aims of Application
Clause 5 - Rules for the Application of Modular Coordination
What is the basic module (M) that forms the basis of modular coordination?+
The basic module 'M' is 100 mm. All other preferred dimensions are multiples or sub-multiples of this value.
What is the purpose of a planning grid?+
A planning grid is a reference system of orthogonal lines used to locate and coordinate the position and size of building elements, spaces, and components (Clause 6).
How does modular coordination relate component size to grid size?+
The component's 'work size' is derived from the modular grid space, subtracting allowances for joints and manufacturing tolerances, ensuring components fit within the grid (Clause 5.3).