Loose Structural Steelwork Fixing
A structural bolted connection was found with the nut and washer not fully seated against the steel plate, leaving a visible gap. This indicates that the fixing may not have been correctly tightened or may have loosened after installation. The connection may therefore be unable to transfer loads as designed and could permit movement, vibration or progressive loosening. It should be assessed and rectified in accordance with the structural design and approved bolting procedure.
- NCQLE reference
- NCQLE-2026-00024
- Quality topic
- Installation quality
- Lesson type
- Near Miss
- Evidence rating
- Experience
- Published
- 2 August 2026
- Last reviewed
- 2 August 2026
Evidence basis: Supported by relevant professional experience. This learning is provided for professional consideration and does not replace project-specific competent advice, statutory duties or contractual requirements.
Context
The issue was identified during an inspection of a structural steelwork connection before the area was enclosed. One of the bolted fixings had a visible gap between the washer and the connection plate, indicating that the assembly had not been fully seated or correctly tightened. The connection formed part of the building’s load-bearing steelwork and required confirmation of its installation and structural adequacy before acceptance. A structural fixing was observed with a visible gap between the washer and the steel connection plate. The nut and washer were not fully seated, indicating that the bolt had not been correctly tightened or may have loosened after installation. This left the connection inadequately clamped and potentially unable to perform as required by the structural design.
The transferable lesson
Structural bolts must be installed, tightened and verified in accordance with the approved design and specified bolting procedure. Visual installation alone is not sufficient: connections require a documented inspection confirming that washers are correctly positioned, nuts are fully seated and the specified tightening or preload has been achieved. Loose fixings should be treated as a potential structural defect and investigated before the connection is loaded, enclosed or accepted.
Recommended action
Implement a documented inspection and tightening procedure for all structural bolted connections. Confirm the correct bolt, nut and washer arrangement; ensure mating surfaces are properly aligned; and tighten each fixing using the method and torque or preload specified by the designer and manufacturer. Mark completed fixings where appropriate, record the inspection results, and carry out a secondary check before the connection is loaded, enclosed or handed over. Any loose fixing should be isolated, investigated and rectified under the structural engineer’s direction.
Limitations and application
The correct tightening and acceptance criteria depend on the connection design, bolt grade, fixing system and whether the bolts are preloaded or non-preloaded. A visible gap may also result from misalignment, distorted steelwork, an incorrect washer arrangement or missing packers, so the defect should not be addressed by simply tightening the nut. The structural engineer should confirm the cause and required remedial action, particularly where the connection has already been loaded or shows signs of movement, damaged threads or deformation.