Cross UK says in a report about basement works that engineers should carry out a full assessment of existing structures when considering alterations.
The UK’s structural safety body has made a number of recommendations in response to an incident in which an inadequate structural design for a basement led to structural distress within a five-storey townhouse.
The incident occurred when a structural engineer was appointed to investigate cracking within a recently altered Victorian house. Changes centered around the removal of a load-bearing wall at the basement level.
The Collaborative Reporting for Safe Structures (CROSS) UK report states: “For the basement works the client engaged an engineer to prepare structural calculations for the works. The engineer proposed openings to be made in the basement prepared a design for a beam (with padstones) over the K. However, the engineer failed to check the supporting walls, piers and foundations.
The report states that a second engineer, commissioned by the client to check the first engineer’s design, approved the design without flagging the original engineer’s failure to check the walls, piers and foundations.
For the basement work, the client did not give notice or award arrangements to other owners within the building as required under the Party Wall etc Act 1996.
The report said that after the completion of the work, cracks appeared in the walls supported by the newly installed beams. A “reporter” called in to investigate found that the modified structural configuration required the walls, piers and foundations to be opened up and assessed.
The report questioned the competence and suitability of both the design and test engineers for the project.
The report states, “While it is not possibly known how close the building was to a serious collapse, it appears that significant structural work was carried out with respect to the stability of structural elements below and above the removed wall. “
Commenting on the incident, an expert panel said: “This is a very worrying report indeed. There were many opportunities to avoid this dire situation. For two engineers to perform so poorly in carrying out their duties, There is no apparent impact on the design proposal for the building control process and for the client to ignore important advice relating to party walls, demonstrating glaring failings that should go unnoticed.
Cross UK made the following recommendations in the report:
For property owners and customers
- Understand the required competencies of engineers for the project at hand
- All structural design must be signed off by an appropriately experienced Chartered Civil or Structural Engineer
For civil and structural design engineers
- Engineers must make a full assessment of existing structures when considering changes
- Designers have responsibilities under the Construction (Design and Management) Regulations 2015
- Consider basing design checks on drawings and specifications as well as calculations
- Be aware that the adequacy of the structural design submitted to the building control body rests with the original designer – do not rely on a building control review
for the creation of control bodies
- Ensure all structures are checked for compliance with Part A of the Building Regulations in England and Wales, and by equivalently qualified and experienced people in Scotland and Northern Ireland