Last edited 11 May 2021

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BSRIA Institute / association Website


Design Framework for Building Services 5th Edition (BG 6/2018), written by David Churcher, John Sands & Martin Ronceray, and published by BSRIA in June 2018 defines a clash as: ‘Two distinct elements occupying the same space. Space for access, installation and maintenance must be allowed for.’

It identifies three types of acceptable clash:

  • Critical: Major clash - must be resolved at this stage.
  • Moderate: Easily resolvable – does not have a major impact on ongoing design. Can be resolved at a future stage.
  • Allowable: Acceptable clash – resolution not required in the design model.


See also: Clash avoidance.

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