Overview
ISO 3443-7:1988 - Tolerances for building, Part 7 (Method 2: Statistical control method) defines an operational procedure for accepting dimensional accuracy of building components and operations using statistical inspection. It is intended for use when contracting parties agree to refer to this part of ISO 3443. The standard covers recognition of specified requirements, acceptance criteria and consequences of rejection, recommended agreements and measurement methods, and planning and executing inspection using statistical control.
Key facts:
- Focus: dimensional tolerances and statistical control in the building industry
- Applicability: all forms, dimensions and positions used in construction
- Use: voluntary - applied only if parties include it in the inspection agreement
Key topics
- Scope and field of application: defines when and how the statistical control method is used for dimensional tolerance acceptance.
- Tolerances and specification recognition: how tolerances should be indicated on drawings or in contracts and how unspecified cases are handled.
- Approval criteria: rules for acceptance/rejection of individual items and lots based on measurements and sampling.
- Inspector responsibilities: designation, duties (sampling plans, lot formation, measurement supervision, calibration checks, recording results).
- Procedures for defective items: judgement of applicability, repair and retest rules, exceptions for remeasurement.
- Statistical inspection techniques: planning and execution of sampling-by-attributes and variables, references to sampling tables and charts (annexes include tables and statistical definitions).
- Measurement methods: recommendations and references to measurement standards for consistent dimensional verification.
- Integration with other standards: references ISO standards for sampling (ISO 2859, ISO 3951), statistics (ISO 3534), drawing indication (ISO 6294), and measurement methods (ISO 7077).
Applications
Who uses it:
- Quality managers and control engineers in construction and prefabrication
- Site surveyors and measuring technicians
- Suppliers, fabricators and contractors responsible for dimensional compliance
- Inspectors and acceptance authorities managing lot sampling and conformity assessment
Typical uses:
- Defining acceptance criteria for manufactured components (doors, frames, precast concrete, MEP modules)
- Planning sampling inspection of lots and subcontracted components
- Establishing measurement protocols and inspection agreements between supplier and client
- Implementing statistical process control for dimensional conformity on site or in factory settings
Related standards
This part of ISO 3443 is intended to be used alongside related ISO publications, including (but not limited to):
- ISO 3443-6 (Method 1 - short method for approval criteria)
- ISO 2859 series (sampling procedures and tables for inspection by attributes)
- ISO 3951 (sampling by variables)
- ISO 3534 (statistics - vocabulary and symbols)
- ISO 7077 (measuring methods for building)
- ISO 6294 / ISO 4464 (indication and relationship of tolerances on drawings)
Using ISO 3443-7 helps organisations apply consistent, auditable statistical methods for dimensional tolerance control - improving acceptance decisions, reducing disputes, and supporting contractual clarity.