Recommendations for modular co-ordination: notations and symbols for modular drawings
1986 Edition

This section defines the extent of IS 11775, focusing on modular coordination concepts applied in building drawings. It emphasizes the use of standardized grid lines and measurement units to enhance clarity and uniformity.

Key details include grid line intervals differentiated by line thickness and style, and adherence to the International System of Units (SI) for all dimensional quantities. The standard aligns with global practices while adapting to Indian construction contexts.

Defines modular grid lines as primary reference lines used in structural layout and design. It describes planning these lines at consistent intervals, commonly from 3 to 6 meters, to optimize material use and construction efficiency. Identification is done using letters along one axis and numbers along the perpendicular axis, creating a clear coordinate system for element placement. Modular dimensions are multiples of a base increment, typically 300 mm.

Centre lines indicate the precise axes of structural elements like walls, columns, and beams. They are depicted on drawings using thin dashed lines with distinct centre markings at each end. These lines serve as essential control references for accurate layout and dimensioning, ensuring consistency throughout construction.

This section specifies the form and positioning of arrowheads terminating dimension lines. Arrowheads are short strokes forming angles between 15° and 90°, and can be open, closed, or filled. Placement is preferably within the dimension line, but may be outside if space is limited. Numerical dimension values are positioned adjacent to arrowheads on the dimension line for readability.

Clarifies the concept of modular space as the fundamental unit of measurement in modular coordination, usually taken as 100 mm or 300 mm. Modular dimensions are defined as multiples of this module, facilitating design standardization and component interchangeability. The notation 'M' is used to represent the module size, with dimensions expressed as n times M.

Describes graphical conventions for illustrating facade corners in modular drawings. Thin dashed or continuous lines with square end marks symbolize facade corners, indicating the building's reference framework. When facade corners coincide with axial lines, circles replace squares at line ends. The standard uses alphanumeric grid references to accurately locate structural elements.

Defines neutral zones as transition areas between modular or non-modular elements. Modular neutral zones are represented by thin dashed lines ending with circles, while non-modular zones end with half-circles. These graphical notations aid in clarifying interfaces and detailing in modular construction layouts.

Modular dimensions are standardized sizes expressed as integer multiples of a fixed module 'M'. The standard distinguishes between modular, working, and checking dimensions, with working dimensions including allowances and checking dimensions used for verification. Non-modular dimensions accommodate sizes outside the modular grid, used when precise modular sizes are impractical.

Non-modular dimensions refer to sizes that do not conform to the standard modular multiples. They provide flexibility for custom measurements needed for architectural or specific functional requirements. This section discusses their use alongside modular dimensions, including manufacturing tolerances and quality control considerations.

Checking dimensions are critical measurements shown as continuous thin lines with small clockwise slant marks, used to verify essential clearances and sizes such as widths and heights. The code recommends combining modular, working, and checking dimensions on drawings to ensure accuracy and proper fit.

Erection sequence is depicted by numbers enclosed within squares, indicating the order in which structural components should be assembled. Element positioning uses a grid system with alphabetic labels on the horizontal axis and numeric labels on the vertical axis, facilitating precise location identification during construction.

Details the identification system for modular and reference lines on drawings, which includes numbering or lettering lines spaced typically at multiples of 100 mm. Primary modular lines use bold continuous strokes, while secondary lines may be dashed or thinner. Symbols indicate intersections and line types to maintain clarity.

This section covers the use of specific line types and end symbols for section markings. Section lines are thin dashed or continuous lines ending with a circle inside a diamond or a diamond alone, depending on the clause. Modular grid lines use thin, thick, or chain lines with diamond end marks to represent different intervals and axial positions.

Explains the combined use of modular (base units), working (actual construction sizes), and checking (verification measurements) dimensions within the same drawings. It highlights the importance of distinct symbols for each type to facilitate cross-verification and maintain consistency in modular coordination.

Provides an overview of standardized graphical symbols and notation systems used for modular coordination. It includes codes for architectural elements such as doors, windows, partitions, and fixtures, with alphanumeric identifiers to ensure clarity. The section reinforces the importance of using these conventions to maintain uniformity across modular construction documentation.