Glossary of terms relating to modular coordination
1983 Edition

The basic module (M), according to IS 4993, is the core measurement unit standardized at 100 mm, used as the foundational size for dimensioning building components and layouts. This module serves as the basis for modular coordination, where components and assemblies are sized in multiples or fractions of M to ensure uniformity and simplify design. The use of this standard unit reduces the variety of component sizes and enhances flexibility in architectural and structural planning.

IS 4993 differentiates modular components and modular elements by their scale and function. A modular component is a smaller, individual part whose dimensions conform to the modular sizing system, while a modular element is a larger assembly or unit, often comprising multiple components, that also adheres to modular dimensioning principles. Both types are designed to fit within a modular grid framework to facilitate coordinated construction and ease of assembly.

While IS 4993 establishes modular sizes as multiples of a basic module, it outlines permissible deviations as the maximum allowed differences from nominal sizes. Typically, tolerances vary with module size: ±0.5 mm for modules up to 50 mm, ±1.0 mm for modules between 51 and 150 mm, and ±1.5 mm for modules larger than 150 mm. These guidelines help maintain interchangeability and ensure proper fitting of modular components, though precise values should be confirmed against the latest standard or project requirements.

According to IS 4993, modular grids consist of two-dimensional rectangular coordinate systems with lines spaced according to the basic module or its multiples in horizontal directions. Modular planning grids apply this concept specifically for building layouts. Space grids extend this concept into three dimensions, either as a basic modular space grid with equal spacing along all axes or as modular space grids where spacing may vary by axis. This structured approach promotes dimensional consistency and flexible design coordination.

IS 4993 uses terms such as Modular Component, Modular System, and Modular Surface to describe the relationship between building parts and the modular reference framework. A Modular Component is an individual part sized according to the modular system, which is the set of rules ensuring dimensional compatibility. The Modular Surface represents the theoretical plane of a component aligned with modular dimensions, facilitating uniformity and interchangeability within the modular coordination system.