Overview
EN ISO 6284:2024 (identical to ISO 6284:2023) specifies methods for indicating limit deviations on construction documents. Published by CEN and prepared by ISO/TC 10, this standard defines how to present tolerance information both graphically (on drawings) and alphanumerically (in data templates/BIM) so that limit deviations are clear, consistent and usable for both humans and machines.
Key topics
- Scope and purpose: methods for indicating upper and lower limit deviations relative to a target size when there is a functional need to control position, dimension, orientation or form.
- Terms and definitions: builds on ISO 286-1 and ISO 6707-1 for concepts such as limit deviation, upper/lower limit deviation and target size.
- Two indication methods:
- Dimensions on construction drawings or notes - numerical indications placed with the relevant dimension (values in millimetres or metres); conventions for asymmetrical deviations, explicit zero values and symmetric tolerances are specified.
- Property items within data templates - natural-language property items for machine-readability supporting BIM and digital exchange.
- Designation of deviation types: common codes are recommended (examples: LD = Length deviation, AD = Angular deviation, PL = Profile deviation of a line, SL = Straightness, SS/FS = Surface shape/flatness, PP = Position of a point, VD/HD = Verticality/Horizontality).
- When to apply: a limit deviation is required only if there is a functional requirement to control the related attribute.
- Human + machine-readability: acknowledges the need for both graphical presentation and standardized data structures (e.g., ISO 23387-style templates) for digital workflows.
Applications
- Architects and engineers - specify tolerances and allowable deviations on construction drawings and models.
- BIM managers and CAD technicians - encode limit deviations in data templates to support automated checks and data exchange.
- Manufacturers and prefabrication suppliers - ensure products fit on site by communicating acceptable deviation limits.
- Contractors and site teams - use documented deviations to make on-site decisions, reduce rework and improve quality control.
- Quality assurance - inspection, conformance checks and acceptance criteria tied to documented limit deviations.
Related standards
- ISO 286-1 (tolerances on linear sizes)
- ISO 6707-1 (building vocabulary)
- ISO 9431 (drawing text spaces and title blocks)
- ISO 23387 (data templates for construction information)
- ISO/IEC directives and ISO 5127 referenced for broader terminology and document practice
By following EN ISO 6284:2024, organizations can standardize how tolerances and deviations are presented across drawings and digital models-improving clarity, reducing errors and enabling better integration of BIM and prefabrication workflows.
