Attaining a new level of precision in construction

After a long interval, the British Standard on tolerances and accuracy in construction has been fully revised. This blog post explains what the standard does and what’s new.

The fact is that BS 5606 was last revised in 1990. That was the year that Nelson Mandela was freed from prison after 27 years of captivity and Mikhail Gorbachev became the last president of the Soviet Union. Sinead O’Connor released Nothing compares with you and the first human gene experiment was conducted. In other words 1990 is a date from history. It’s a generation ago. BS 5606 badly needed to be updated, and happily that’s what’s happened now.

Accuracy and tolerance

What does BS 5606 do? Quite simply, the standard explains the principles that underpin accuracy and tolerance in construction projects, and gives examples of the challenges associated with the fit of elements and components of construction. So essentially, it’s about how to avoid problems on building sites that can arise when components don’t fit together.

It’s the case that in any building or manufacturing process there’s always some degree of dimensional variability. This happens because of the physical limitations of operatives and the inherent variability of tools, measuring equipment and materials. BS 5606 deals with the dimensional variability that arises during the building process.

And of course, this is a problem that has grown over time. Given digital technologies and modern methods of construction, and given that substantial components are often manufactured offsite, tolerances matter more than ever if onsite and offsite elements from steel frames and proprietary roofs, to internal partitions and sophisticated electrical and heating services are to fit together as required. Hence the revision.

How the standard works

BS 5606:2022 Accuracy and tolerance in design and construction – Guide applies to buildings and civil engineering works and helps users avoid or resolve problems of inaccuracy or fit by assessing the dimensional needs of a design regarding tolerances, and then designing and specifying appropriately. Those users will largely be architects and designers, structural engineers, building services engineers, construction product manufacturers, housing developers, surveyors, contractors and builders.

The standard also helps these professionals to assess the likely achievement of tolerances specified for a particular project, and it helps them monitor and control work during construction to ensure that it’s in accordance with specifications. The standard also guides the accuracy of surveys undertaken pre, during and post construction to measure existing features and as-builts, so they support the ability to achieve design tolerances and fit.

Revisions to the standard

For 2022, expert reviewers from across the construction sector completely revised the standard to reflect modern day tolerances and modern-day construction materials and processes including digital technologies, BIM (Building Information Modelling) and offsite construction. Updates have been made to the examples in the standard as well as to the technologies and processes covered.

Minor updates have been made to historical tables in the standard, but in fact construction tolerance data from the 1970s and 1980s - from the standard’s first incarnation - has been retained. This is because it still has a usefulness for today’s builders.

The overall result is a standard that now provides a comprehensive and data-rich source of guidance on construction tolerances that will help users to attain a new level of accuracy and fit, and avoid time-consuming problems. The standard also provides help with relating design tolerances to construction or manufacturing tolerances - a key area given the increasing adoption of computer modelling tools in construction processes.

No longer an historic document, BS 5606 is now fit to serve the future of a transformed and transforming construction sector.