DESIGN AUDITS

The design of roofs in the UK often takes place in a 'piecemeal' fashion, with different parties taking individual design decisions and sometimes working in isolation. This fragmented process was described in an article published in RCI in February/March 1996. For some projects, there is a need for a more co-ordinated approach to roof design to ensure that the completed construction is robust and will last. This is appropriate for projects where there is an unusual roof shape, an exposed site, extreme internal conditions such as pool halls or possibly a prestigious building with a long design life.
To check a proposed construction, perhaps as part of a quality system, design audits are carried out. But what design tasks should this include and is there a systematic approach?

Design Task Check List

For the past couple of years we have used a check list which identifies specific design tasks and the relevant current British Standard. Not every task identified is necessarily appropriate for a given project, although, it is helpful to be reminded of the wider issues. Alternatively on some projects there may be additional specific design requirements since the check list is not exhaustive.
As with most check lists they can soon become outdated, especially with the frequent issue of revised British Standards. Three of the main standards covering the design of roofing systems have been revised in as many years. In the future Eurocodes will be introduced, but currently the timetable for their implementation appears to be several years away. As well as the British Standards given there are many other good authoritative design guides published by Trade Associations and manufacturers, although there are too many to list in this Technical Note.

Design Audits

Design audits should be carried out by competent and experienced people. As a minimum they require a copy of the current version of the British Standard together with a working understanding of its contents. Appropriate time should be allowed for a design audit, recognising that conclusions reached may require changes to the roof to be constructed.

Conclusion

In the increasingly litigious world where the responsibilities of the parties are more clearly defined, those carrying out design work need to have professional indemnity insurance to cover a potential claim in the event of a design error. With the trend to adopt more complex lightweight 'engineered' roofing systems, there is a greater need for a more rigorous approach to the design of roofs in the UK.

References

© Keith Roberts, 1998
First published in Roofing Cladding Insulation, April 1998

Important Note: Readers should check that they are using the latest version of the relevant Standard

RCI Technical Notes

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