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IS 11775:1986 is the Indian Standard (BIS) for recommendations for modular co-ordination: notations and symbols for modular drawings. This standard provides recommendations for a unified system of notations and symbols for use in modular drawings. It aims to standardize the graphical language for modular grids, levels, components, and joints to ensure clarity and consistency in construction documents, particularly for prefabricated and system-built projects.
Recommendations for modular co-ordination: notations and symbols for modular drawings
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
! This standard is the graphical 'language' for the principles of modular coordination outlined in IS 11774.
! Essential for architects and drafters working on prefabricated or system-built projects to ensure clear communication with manufacturers and site teams.
! The concepts of standardized grids and component symbols are foundational to modern BIM workflows, making this standard conceptually relevant even today.
Collaborative production of architectural, engineering and construction information — Code of practice
A broader code for construction drawing practice that includes conventions for grids and dimensioning.
ISO 128-20:2020ISO (International Organization for Standardization)
LowCurrent
Technical product documentation (TPD) — General principles of presentation — Part 20: Basic conventions for lines
Specifically covers the types and conventions for lines used in technical drawings, a component of IS 11775.
Key Differences
≠IS 11775:1986 is a standalone document focused only on notations for modular drawings, whereas modern international practice integrates these notations into broader standards for digital information management and BIM, such as the ISO 19650 series.
≠The Indian standard is based on 1980s manual drafting techniques and is still officially 'current'. Its direct international equivalent, ISO 8560:1986, has been withdrawn, reflecting a shift in international standardization towards more comprehensive drawing systems.
≠While the principle of indicating modular size is shared, the notation can differ. IS 11775 suggests writing the modular size (e.g., 30M) above the dimension line, while ISO 2848 suggests writing the modular number in brackets next to the work size, e.g., 2990 (30M).
Key Similarities
≈Both IS 11775 and international standards (stemming from ISO 2848) are founded on the same basic module 'M' of 100 mm as the fundamental unit of measure.
≈The graphical convention of using a structural grid with alphanumeric locators (e.g., A, B, C... and 1, 2, 3...) enclosed in circles at the end of grid lines is a common practice in both the IS code and international standards like ISO 8560.
≈Both systems use thin, non-continuous line types (e.g., chain line, dashed line) to represent the modular grid, distinguishing it visually from the solid lines used for building components.
≈The use of specific symbols to denote reference levels and planes, such as the finished floor level (FFL), is a shared concept, even if the exact graphic varies slightly.
Parameter Comparison
Parameter
IS Value
International
Source
Basic Module (M) Value
100 mm (defined in the referenced IS 10213)
100 mm
ISO 2848:1984
Grid Line Type
Thin continuous line or long-dashed dotted line (as per IS 10714)
Thin chain line (long dash, short dash)
ISO 8560:1986
Grid Line Identification Symbol
Circle of approx. 10 mm diameter containing the grid number/letter.
Circle at the end of a grid line containing the identification.
ISO 8560:1986
Floor Level Symbol
Circle bisected by a horizontal line, top half shaded, with level value.
Circle with a horizontal arrow pointing to the reference face, with level value.
ISO 7519:1991 (Withdrawn)
Component Deviation from Grid
Indicated by a small dimension with an arrow from the component to the grid line.
Indicated by a secondary dimension from the component to the grid line.
ISO 8560:1986
Standard Status
Current (Reaffirmed 2021)
Withdrawn (without direct replacement)
ISO 8560:1986
⚠ Verify details from original standards before use
Key Values0
No quick reference values available for this code yet.
Tables & Referenced Sections
Key Tables
No tables data
Key Clauses
Clause 3 - Symbols for Grids
Clause 4 - Symbols for Indicating Storey Heights and Levels
Clause 5 - Symbols for Components
Clause 6 - Symbols for Joints
Clause 7 - Notations for Dimensions
Frequently Asked Questions4
What is the symbol for a basic module (1M) grid line?+
A thin continuous line with a small circle at its end containing the grid reference (Clause 3.1).
How is a structural floor level indicated?+
Using a solid black triangle pointing downwards, placed next to the level dimension (Clause 4.1).
What symbol is used to identify a non-modular component?+
An arrow pointing to the component with the letter 'N' enclosed in a circle (Clause 5.3).
How are multimodular grid lines represented?+
By a long-dashed dotted line with a small circle at its end (Clause 3.2).