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CROSS Safety Report

Inadequate design submissions for alterations to an existing building

Report ID: 1085 Published: 10 March 2022 Region: CROSS-UK

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An upper storey extension was designed without considering the effect on the structure below. A further four attempts to prove the proposed new structure failed to demonstrate adequacy.

Key Learning Outcomes

For owners and clients:

  • Ensure engineers are competent for the project in hand before appointing

For all built environment professionals:

  • Work within the limits of your competence
  • All professionals should understand the code of conduct of their qualifying institution(s), which they are obligated to uphold
  • Codes of conduct will require professionals to apply appropriate skills, experience, and knowledge

For civil and structural design engineers:

  • Supervision of design by experienced engineers can allow less experienced engineers to develop their competence
  • Engineers should undertake full assessments of existing structures when considering alterations
  • Independent checking is good practice

Full Report

Find out more about the Full Report

The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


A report has been received from a consulting engineer who was appointed to check the design for an upper storey extension. The check was part of a landlord’s consent process.

The checking engineer found that the structural design did not consider the effects on the existing structure below. When asked why they had not done checks on the existing structure, the design engineers did not appear to understand the need to assess the supporting structure. After accepting the need to assess the existing structure, calculations were re-submitted, but these proved to have very significant errors.

A second re-submission was made, and this also contained serious errors. A third, and then fourth re-submission were made; the last two versions had apparently been reviewed by a chartered engineer at the design practice. None of the submissions adequately justified the proposals.

The design firm responsible appeared to have little understanding of lateral stability considerations

The design firm responsible appeared to have, in the view of the reporter, little understanding of lateral stability considerations. The Landlord was told that the calculations were insufficient to prove that the building was capable of accepting the proposed upper storey extension. Subsequently, a second design practice was engaged to design the upper story extension. 

Unsurprisingly, the reporter concluded that designs for additional storeys should only be undertaken by competent people.

Expert Panel Comments

Find out more about the Expert Panels

Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

This is a worrying report. That several attempts were made without success to justify the structure suggests that the designers may have been working outside their knowledge and experience.

Engineers should always be mindful of their professional duties under law, their terms of appointment and the code of conduct of their qualifying institution. The code of conduct alone will require them to be competent to perform the duties offered, apply appropriate skills, experience and knowledge, to act with impartiality and have full regard for safety. It would be very unwise indeed for any engineer, or indeed other building professional, to act outside of their obligations. An engineer acting outside of their competence, as appears to be the case here, is a very serious issue that may well lead to unsafe structures.

An engineer acting outside of their competence is a very serious issue that may well lead to unsafe structures

The value of independent checks

It is foreseeable that mistakes will occur however the supervising senior engineer should have identified all shortcomings when checking the design. It is fortunate in this case that an independent check was required as this led to the discovery of the inadequate design. The value of independent checks should not be underestimated since not only are errors found but learning and development across teams are facilitated.

Clients should assess competency before appointing

Clients should always be concerned to understand the competence of building professionals they propose to appoint. Capability in terms of the experience, training and qualifications should be assessed alongside the proposed resourcing. The firm’s checking and validation protocols should be appropriate to the complexity of the work in hand.


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