Standards Development

Scope

This document specifies the classification criteria for prefabricated buildings, including structural material, dimensions of prefabricated components, construction method, degree of assembly, as the design service life. It further defines the classification principles and the applicability boundaries for each category.

NOTE: This document applies to the design, production, construction, and related activities of prefabricated buildings, including newly constructed buildings, renovation projects, and extension projects incorporating prefabricated components, in the residential, public, and industrial building sectors. This document does not apply to temporary buildings intended for short-term use.

Purpose

The core goal of this standard is to unify technical terminology. Currently, terms like "precast", "modular" and "prefabricated" are often mixed and misused across different countries, with unclear conceptual boundaries that severely impede international technical exchanges and mutual recognition in trade. By drawing on the terminology foundation of ISO 25084, the standard offers unified classification terms and definition criteria for all stakeholders.

Additionally, it establishes a five-dimensional classification framework, which accurately describes buildings from five aspects: structural materials, prefabricated component dimensions, construction systems and technologies, prefabrication degree, and design service life. This addresses the limitation of existing national standards, which typically only classify buildings from a single dimension. Furthermore, the standard covers the entire life cycle of construction activities, including design, production, construction, acceptance, and maintenance. It is applicable to new construction, reconstruction, expansion projects, as well as various types of building fields.

Justification:

To meet the urgent needs of the committee's subsequent work: when ISO/TC59/SC19 Prefabricated Building Subcommittee advances follow-up work in the field of prefabricated buildings, such as formulating subsequent technical standards, conducting industry data statistics, and promoting technological achievements, it requires a set of unified classification standards as the basic support to ensure the consistency and effectiveness of various tasks. Therefore, the project approval of this standard is a necessary prerequisite for the orderly development of the committee's work.

Currently, there are multiple structural gaps in the global prefabricated building field. First, the core terminology system is chaotic. The connotations and extensions of concepts such as "precast", "modular" and "prefabricated" vary significantly in different national contexts, resulting in a lack of a unified linguistic foundation for technical exchanges and trade. Second, the classification dimension is single. Existing national standards either focus on structural materials or prefabrication rate evaluation, and no comprehensive framework has been formed that can simultaneously cover material properties, component dimensions, construction technologies, prefabrication degree and service life, making it difficult to accurately portray complex building systems.

Third, emerging systems such as bamboo structures, container buildings and various mixed structures are developing rapidly, while current international standards mainly focus on traditional materials such as concrete, steel and wood, resulting in an obvious lack of classification and positioning for the above systems.

Fourth, there are significant differences in the definition and evaluation methods of prefabrication degree among various countries, either based on the proportion of on-site workload or the value of off site manufacturing, and there is a lack of internationally general classification methods that do not rely on specific national parameters.

Fifth, there are essential differences between temporary buildings and permanent buildings in terms of structural design, safety requirements and durability standards. However, due to the lack of unified definition criteria, standards vary among countries in regulatory practices, which not only causes resource misallocation but also brings potential safety hazards. Sixth, cross-border trade of prefabricated building components and modules is growing day by day, but the certification standards and testing methods of different countries are difficult to be mutually recognized, and the industry is in urgent need of an internationally general product identification system.

The existence of the above problems makes it an urgent task to establish a classification standard that is connected with the ISO 25084 terminology system, covers multi-dimensional attributes, and takes into account both traditional and emerging systems. This standard is not only a necessary supplement to the existing international standard family but also a basic prerequisite for promoting global technical exchanges, unimpeded trade and mutual recognition of supervision in the field of prefabricated buildings.