Post 519  by Gautam Shah


SI (French: Système International d’Unités, SI) is a derived set of Measurement Units factored by x1000. ISO Modulor Preferences (International Organization for Standardization) are prescribed sets of Measurements in consideration of the traditional choices, commercial practices and rational applicability.

Mill Owners’ Association (ATMA) Building, Ahmedabad India by Le Corbusier Wikipedia image by Author Sanyam Bahga

SI Recognized Measures: The SI system recognizes three sets of measures, in each of the major categories. This is a 1000-factored gradation. No interim measures like the most widely employed centimetre is to be used.

The SI Recognized Measures are:

             Length         mm    mt       km

             Weight         mg     kg       T

             Volume        ml       Lt       kl

Such 1000 factored unitization was not considered suitable for many commercial activities, planning and dimensional coordination. The next step was the ISO modular system of Modular preferences, based on SI system (a derivative of the metric system). This type of Modular Coordination of Dimensions, though, is unnatural and does not exactly relate to human body. Its implications to our senses are extremely limited. It creates an ‘order that lacks beauty’. The system does not harmonize the variable tolerances’ requirements, and differences in fitment sizes. ISO modular preferences in spite of the universal acceptance do not fully resolve all the anomalies of the world’s commercial processes.

Size modulated play units Lego

There are many products where smaller modulation or variations are desirable such as Garments and Shoes. ISO Modular Preferences, do not consider the variations in naturally available materials. Furniture, fittings and fixtures designed with ergonomic profile or serving anthropometric, inconsistencies have no specific accommodation in this system.

Array of bricks Wikipedia image by Author Thamizhpparithi Maari

ISO Modular Preferences, however, as a universally agreed system of preferred measures, disciplines design, procurement, production, conveyance, handling, storage, distribution, usage, wastage and reuse or recycling of materials. The system has provided a level ground to compare standards of various countries, and evolve world standards (ISO) for various products, services and work or operational procedures. It has made the writing of specification lucid and logical. It simplifies taxation procedures, costing, estimating, and valuation. It also rationalizes deployment of human and energy resources. It has made quality control procedures very objective.

Modulated Grid Plan Salisbury Cathedral

ISO is a modular system to form a grid or matrix for macro planning and in that sense takes a superior position. Components and parts are expected to fit in the system. As a result, work-sizes of components and assemblies should be determined by taking account of space for joint and allowance for tolerances. ISO Modular system has very simple and predictable progression-digression, unlike many mathematical orders and systems like Corbusier Modulor system.


Survey of India Triangulation Map

In spite of IS recognized measures and ISO Modular preferences, at any cross section of time, there are many creative people, who feel stifled by such an Abstract Dimension Modulating System. But one must also concede that by its universal acceptance (through ISO), a logical dimensioning tool has been made available to a vast majority of people. The Dimensioning Tool defies all localized traditions, cultural variations, anthropometric distinctions, racial biases and geographical peculiarities. The system is unaffected by time or space.

Building Grid Image from Flickr by Peter Alfred Hess

ISO’s Four Preferences for Modular Coordination:

The Foot-inch equivalent measures were shown as a carry-over or interim arrangement.

● First Preference               300 mm = 12″

● Second Preference         100 mm = 4″

● Third Preference              50 mm = 2″

● Fourth Preference           25 mm = 1″

First Preference is favoured by the building materials’ industry. Plywoods and other wood products are available in modules of 300 such as 600, 900, 1200, 1800, 2400 etc. Large buildings are designed with 300 as the modular measure. But, for smaller spaces such as Bedrooms, toilets, second preference of 100 is used as a module.

Second Preference is considered to be the most appropriate one for Building components and Planning. Glazed Tiles are available in multiples of 100 mm, with sizes like 100 x 200, 200 x 200, 200 x 300 etc., and also in sizes such as 150 x 150, 150 x 200 etc. as a carry over from the old system. Fabrics have widths of 600, 900, 1000, 1200, 1800 etc. When we order Windows or Doors the width x height are measured in 100 mm increments.

Third and Fourth Preferences are more preferred for objects smaller then 300 sizes. These preferences are not to be used for basic object sizes of more than 300, unless there are strong economic or functional reasons for doing differently.


Mother-Boards Sizes in ISO Modules