Recommendations for modular coordination in the building industry: Horizontal co-ordination
1987 Edition

IS 7921 - Defining the Scope: Core Specifications & Tables

This standard governs the selection of preferred controlling dimensions for building elements such as doors, windows, and furniture, tailored for diverse building classifications to promote modular coordination and uniformity.

Highlights:

• Controlling dimensions set normative widths, heights, and spacing standards.
• Variations exist per building category: Educational, Residential/Industrial, Health/Office.
• These dimensions aim to streamline modular design, construction efficiency, and cost-effectiveness.

Sample Preferred Controlling Dimensions

Note: The symbol “selected” identifies preferred sizes.

Units & Symbols (SI Units)

Application Details:

• Clause 9.1 specifies door, window, and fixture widths per Table 1.
• Boundary planning (Clause 4.5) affects component placement.
• Modular dimensions simplify design, purchasing, and building phases.

flowchart LR
    A[Building Classification] --> B[Choose Interval]
    B --> C[Select Recommended Size]
    C --> D[Apply Modular Dimension]
    D --> E[Design Doors, Windows, Furniture]

Refer to Tables 2, 3, and 4 in IS 7921 for comprehensive dimension details.

IS 7921 - Application Domain: Essential Specifications & Tables

The standard establishes multimodule values and preferred horizontal coordinating dimensions for buildings and their components, including doors, windows, furniture, columns, and walls.

1. Usage Scope

• Applicable across all building categories: educational, residential, industrial, health, and office.
• Dimensions selected based on functional requirements, structural considerations, manufacturing, economic factors, and transport logistics.

2. Preferred Controlling Dimensions (in mm)

3. Multimodule Series

• Regular series include: 3M, 9M, 15M, 21M, 27M, 33M, 39M, 45M (M = module size).
• Preferred sizes noted with a “selected” indicator in the tables.

4. Units and Symbols (SI)

• Length: metre (m)
• Force: newton (N) equivalent to 1 kg·m/s²
• Pressure: pascal (Pa) equals 1 N/m²

Example Table Extract (Educational Buildings - 12m Interval)

IS 7921 - Definitions and Core Specifications Overview

1. Definitions (Clause 3.1):

   • Based on IS 4993-1983 and IS 6408-1971 foundational terms.
   • Additional definitions specific to this standard are also included.

2. Preferred Controlling Dimensions for Educational Buildings (Clause 10.3 & Table 4):

   • Standardized in millimeters with modular series such as 3m, 9m, 15m, 21m.
   • Examples: 1200, 2400, 3600, 4800, 6000 mm with preferred sizes marked.

3. SI Units and Symbols:

   • Length: metre (m)
   • Mass: kilogram (kg)
   • Time: second (s)
   • Force: newton (N) = 1 kg·m/s²
   • Pressure/stress: pascal (Pa) = 1 N/m²
   • Energy: joule (J) = 1 N·m
   • Power: watt (W) = 1 J/s

4. Application of Controlling Dimensions:

   • Applies to widths of doors, windows, and fixtures (Clause 9.1).
   • Facilitates modular coordination and standardization in design.

Sample Table Extract (Educational Buildings)

Modular Coordination Flowchart

graph LR
A[Building Elements] --> B[Doors, Windows, Fixtures]
B --> C[Controlling Dimensions]
C --> D[Modular Series: 3m, 9m, 15m, 21m]
D --> E[Design Implementation]

IS 7921: Overview of Horizontal Coordination

This principle ensures alignment of building components on horizontal planes to facilitate simplified design, manufacturing, and construction.

Essential Elements:

• Controlling Zone (Clause 3.1.3): A spatial region between controlling planes (floors, roofs, load-bearing walls, columns) governing horizontal modular coordination.

• Modular Grid System: Building parts are designed on a modular grid, usually based on a module size (M), such as 100 mm or 300 mm, standardizing dimensions.

Typical Specifications:

• Module (M): Base measurement unit for horizontal coordination.
• Horizontal modules define widths, openings, component sizes as multiples of M.
• Controlling planes are vertical alignments with structural elements maintaining modular consistency.

Sample Dimension Table

Advantages:

• Simplifies manufacturing and installation.
• Minimizes material waste.
• Enhances interchangeability.

flowchart LR
    A[Controlling Plane] --> B[Controlling Zone]
    B --> C[Floor]
    B --> D[Roof]
    B --> E[Load-bearing Wall]
    B --> F[Column]
    G[Module M] --> H[Horizontal Dimensions]
    H --> C
    H --> D
    H --> E
    H --> F

Summary: Horizontal coordination leverages a modular grid aligned with controlling zones to standardize horizontal dimensions, boosting construction efficiency and uniformity.

IS 7921: Summary of Preferred Horizontal Sizes

• Clauses 2.2 and 4.5 emphasize preferred horizontal dimensions for designing building elements influenced by boundary planning.

• Residential buildings (Clause 11.1) should use multiples of 3 meters for horizontal dimensions.

• Industrial buildings (Clause 8.2) adopt preferred horizontal modules, using standard unit multiples.

Key Table: Residential Horizontal Dimensions

Design Implications:

• Utilize 3-meter modular increments for beams, columns, and room sizes.
• Promotes standardization, cost savings, and simplifies building processes.

flowchart LR
    A[Boundary Planning] --> B[Preferred Dimensions]
    B --> C[Residential: Multiples of 3m]
    B --> D[Industrial: Preferred Modular Units]
    C --> E[Room Sizes, Structural Grid]
    D --> F[Component and Room Dimensions]

Recommendation: Use multiples of 3 meters as the basis for horizontal planning in residential and industrial structures.

IS 7921: Core Points and Equations for Modular Room Dimensions

• Modular Room Dimension Equation (Clause 7.3):

  [ \text{Room dimension} = n \times M + \Delta ]

  where:

  • ( n ) = integer count of modules
  • ( M ) = base module size
  • ( \Delta ) = adjustment:
    • +10 mm when plaster is applied
    • +30 mm without plaster

• Clear room dimensions exclude plaster and include a ±5 mm tolerance to ensure modular fixtures fit correctly.

• Modular planning (Clause 6.2) mandates that all fixtures, fittings, and partitions conform to modular room dimensions without on-site modification.

• Practical note (Clause 7.4): Exact modular room sizing is challenging during carcass construction owing to wall thickness economics and construction tolerances; thus, modular room dimensions are typically not employed for carcass design.

Summary Table: Modular Room Dimensions

flowchart TD
    A[Define Module Size M] --> B[Choose Integer n]
    B --> C[Calculate: n x M + Δ]
    C --> D{Is Plaster Applied?}
    D -- Yes --> E[Add 10 mm]
    D -- No --> F[Add 30 mm]
    E & F --> G[Apply 5 mm Tolerance]
    G --> H[Fit Modular Fixtures Without On-site Alteration]

Note: This modular method guarantees prefabricated components fit seamlessly, minimizing field adjustments.

IS 7921 - Essentials of Axial Planning

1. Definition (Clause 4.3)

• Axial planning determines the location of structural elements like columns, load-bearing walls, and beams by aligning them along shared axes for structural efficiency.

2. Integration with Boundary Planning (Clause 4.4)

• Axial planning can be combined with boundary planning (which is based on building edges) to optimize overall layout.

3. Modular Dimension Compliance (Clause 6.2)

• Modular room sizes must accommodate fixtures and partitions without requiring on-site shaping.

4. Controlling Dimensions (Clauses 4.3-4.5)

• Axial planning governs centerlines of columns, walls, and beams.
• Boundary planning controls the building’s outer limits.
• Modular planning ensures compatibility across all components.

Axial Planning Principle:

• Center-to-center axial spacing should be multiples of the modular unit (e.g., 600 mm, 1200 mm).
• This ensures balanced load distribution and construction simplicity.

Planning Types Overview

graph LR
A[Boundary Planning] --> B[Establish Building Dimensions]
A --> C[Axial Planning]
C --> D[Locate Columns & Walls]
D --> E[Modular Planning]
E --> F[Fit Fixtures & Partitions]

Summary: Axial planning aligns structural components along modular grid axes to facilitate efficient load transfer and construction.

IS 7921: Standard Sizes for Components and Rooms

Highlights:

• Clause 9.1 and Table 1 regulate widths of doors, windows, and built-in furniture, providing standardized sizes for modular coordination.

• Clauses 10.3 and Tables 2, 3, and 4 define controlling dimensions for various building categories, including residential as detailed in Clause 11.

• Clause 8.2 bases dimensions on preferred horizontal modules, typically multiples of 100 mm or 300 mm.

Common Dimensions (from Tables & Clauses):

Room Sizes (Residential Buildings - Clause 11):

• Minimum room width: 2700 mm
• Preferred room length: 3600 mm or multiples of 300 mm
• Minimum ceiling height: 2400 mm

Modular Coordination Illustration

graph LR
A[Preferred Module] --> B[Building Components]
A --> C[Room Dimensions]
B --> D[Doors, Windows, Furniture]
C --> E[Rooms, Corridors, Openings]

Summary:

• Employ modular increments (commonly 300 mm) for all building components and room dimensions.
• Consult Table 1 for component widths.
• Refer to Tables 2-4 for building and room sizing.
• Maintain minimum clearances per residential building guidelines (Clause 11).

For complete details, refer to the full IS 7921 document.

IS 7921: Overview of Controlling Zones and Sub-modules

1. Controlling Zones (Clauses 3.1.3 & 9.3)

• Defined as spaces between controlling planes such as floors, roofs, load-bearing walls, or columns.
• These zones regulate critical dimensions including storey heights, wall thicknesses, and column spacing.
• Dimensions are coordinated within these zones to maintain building component compatibility.

2. Controlling Dimensions (Clauses 3.1.2 & 0.2)

• Dimensions that coordinate modular spacing between controlling points, lines, and planes.
• Examples include floor heights, distances between column centerlines, and wall thicknesses.
• Preferred sizes are aligned with functionality and modular component sizing to minimize variation and enhance standardization.

3. Application of Sub-modules (Clause 9.3)

• Sub-modules represent fractional parts of the main module used to fine-tune dimensions within controlling zones.
• They enable precise coordination where dimensions don’t fit exact multiples of main modules.
• Common sub-module fractions include halves (½), thirds (⅓), and quarters (¼) of the main module.

Typical Modular Coordination Table

Controlling Zones & Sub-module Diagram

graph LR
  A[Controlling Planes] --> B[Controlling Zone]
  B --> C[Main Module (M)]
  B --> D[Sub-modules (M/2, M/3, M/4)]
  C --> E[Floor Height, Column Spacing]
  D --> F[Fine Adjustment of Dimensions]

Summary: Controlling zones and sub-modules provide structured dimensional control to ensure modular compatibility and precise building coordination.

IS 7921: Key Points on Building Dimensions

1. Controlling Dimensions (Clause 10.3)

• Building sizes are regulated primarily by Clauses 11 through 15.
• Refer to Tables 2, 3, 4 and Figure 1 for standard size references.

2. Residential Buildings (Clause 11.1)

• Horizontal dimensions typically follow multiples of 3 meters.
• This modular grid simplifies design and construction workflows.

3. Industrial Buildings (Clause 12)

• Component widths such as doors and windows adhere to Table 1 sizes.
• This standardization eases fabrication and assembly.

4. Coordination Using Sub-modules (Clause 9.3)

• Sub-modules are employed within controlling zones to harmonize component dimensions.
• This reduces waste and enhances modular design.

Sample Table Extract (From Table 2)

flowchart LR
    A[Building Dimensions] --> B[Residential Buildings]
    A --> C[Industrial Buildings]
    B --> D[Horizontal Multiples of 3m]
    C --> E[Component Sizes per Table 1]
    B --> F[Coordination via Sub-modules]

Consult IS 7921 Tables 1-4 and Fig. 1 for detailed dimension and coordination data.

IS 7921: Key Residential Building Dimensions

1. Preferred Horizontal Controlling Sizes (Clause 11.1 & Table 2)

• Dimensions are based on multiples of 3 meters (3M).
• Typical controlling spaces (mm) include:

• Larger intervals such as 6m and 12m are used for bigger spaces.

2. Horizontal Coordination Principle

• Utilizing 3-meter multiples enables efficient design, construction, and component standardization.

Summary

• Apply 3-meter modular grids for residential planning.
• Refer to Table 2 for preferred sizes.
• This approach enhances economic and repetitive design aspects.

flowchart LR
    A[Residential Design Start] --> B[Select Controlling Dimension]
    B --> C{Is Dimension a Multiple of 3m?}
    C -- Yes --> D[Use Table 2 Preferred Sizes]
    C -- No --> E[Adjust to Nearest 3m Multiple]
    E --> D
    D --> F[Apply Horizontal Coordination]
    F --> G[Proceed with Modular Design]

Always consult Table 2 of IS 7921 for detailed residential dimensioning.

IS 7921: Industrial Building Dimension Guidelines (Clause 12)

• Preferred horizontal sizes for industrial facilities (single or multi-storey) are multiples of: 3m, 6m, 12m, 24m, 48m, 96m, and so forth.

• These extended intervals serve as modular units for structural elements and overall planning.

• Refer to Table 2 in IS 7921 for detailed dimension modules suited to industrial applications.

Preferred Dimension Table Extract (from Table 2)

Application Notes:

• Use these sizes for column spacing, bay widths, and structural grid layouts.
• Supports standardization, cost efficiency, and ease of construction.
• Enhances coordination among building elements and fixtures.

flowchart LR
    A[Industrial Design] --> B[Choose Module Size]
    B --> C{Dimension Options}
    C -->|3m| D[Structural Grid]
    C -->|6m| D
    C -->|12m| D
    C -->|24m| D
    C -->|48m| D
    C -->|96m| D
    D --> E[Design Structural Components]
    E --> F[Optimize Building Layout]

This modular framework fosters efficient design and construction of industrial buildings per IS 7921.

Health Building Dimension Guidelines (IS 7921: Clause 13.1)

• Preferred horizontal dimensions for health-related buildings are multiples of 6 meters.
• Refer to Table 3 for controlling sizes (in millimeters) and recommended dimensions.

Table 3: Preferred Controlling Sizes for Health Buildings (mm)

Note: "Selected" indicates recommended sizes.

Summary:

• Employ multiples of 6 meters for modular planning.
• Use controlling sizes from Table 3 for structural design.
• These dimensions guide layout, column spacing, and modular coordination in health buildings.

flowchart LR
    A[Health Facility Design] --> B[Apply 6m Multiples]
    B --> C[Select Sizes from Table 3]
    C --> D[Design Structural Elements]
    D --> E[Achieve Efficient Modular Coordination]

This strategy promotes standardization and cost-effective construction in healthcare buildings per IS 7921.

IS 7921 - Office Building Dimension Guidelines

1. Preferred Horizontal Dimensions (Clause 14.1)

• Recommended horizontal sizes for office buildings are multiples of 6 meters.
• Table 3 provides preferred controlling dimension values.

2. Table 3: Controlling Sizes for Health and Office Buildings

Note: "Selected" denotes preferred dimensions.

3. General Recommendations

• Use multiples of 6 meters for modular planning.
• Align structural grids with preferred controlling dimensions to optimize material use and architectural layout.
• Reference Figure 1 for planning grid displacement considerations.

graph LR
A[Office Building] --> B[Horizontal Grid: Multiples of 6m]
B --> C[Preferred Sizes from Table 3]
C --> D[600mm, 1200mm, 2400mm, 4800mm (3m series)]
C --> E[1800mm, 3600mm (9m series)]
C --> F[3000mm, 6000mm (15m series)]
C --> G[4200mm (21m series)]

This modular approach ensures economical and flexible office building layouts as per IS 7921.

IS 7921: Educational Building Dimension Specifications (Clause 15 & Table 4)

• Preferred controlling sizes (in mm) provide a framework for modular planning in educational buildings, enhancing economy and standardization.

• Modular intervals include 12m, 24m, 48m, 96m, and 192m.

• These dimensions optimize structural grids, room measurements, and overall building layouts.

• Useful for defining beam spans, column spacing, and floor plans.

Summary:

• Use multiples of 3m or 6m for grid spacing.
• Preferred sizes ensure modular compatibility.
• Common controlling sizes include 1200mm, 2400mm, 3600mm, 4800mm, 6000mm, etc.
• Refer to Table 4 in IS 7921 for detailed size selection.

graph LR
A[Educational Building Design] --> B[Select Controlling Dimension]
B --> C{Dimension Series}
C -->|3M Series| D[1200, 2400, 4800, 9600, ...]