EXC/Support Systems/TBT-EXC-026
Adjacent Structure Monitoring During Excavation
Excavations › Support Systems › Adjacent Structure Monitoring During Excavation
Toolbox Talk
Adjacent Structure Monitoring During Excavation
Excavation work near existing buildings, walls, or other structures can undermine their foundations and cause settlement or collapse. Monitoring adjacent structures is essential to detect early signs of movement and prevent catastrophic failure. This talk explains the monitoring methods used, the warning signs to watch for, and the responsibilities of every operative working near existing structures.
Key Hazards
Structural collapse of buildings undermined by nearby excavation
Ground settlement causing cracking and foundation damage
Surcharge loading from spoil heaps destabilising adjacent walls
Vibration from plant operations damaging nearby structures
Control Measures
- Carry out a condition survey of all adjacent structures before excavation work begins.
- Install monitoring points such as tell-tales, prisms, or crack gauges as specified in the method statement.
- Check monitoring readings at the frequency defined by the temporary works designer.
- Keep spoil heaps and heavy plant away from the zone of influence around adjacent structures.
- Report any new cracks, bulging, or movement in nearby buildings immediately to the site manager.
- Ensure excavation support systems are installed progressively as digging advances.
- Follow the temporary works design for sequence and depth of excavation near structures.
- Use low-vibration plant where specified to minimise disturbance to foundations.
- Maintain clear access around monitoring points so readings can be taken without obstruction.
Remember
- Always complete a condition survey of nearby structures before any excavation starts
- Monitoring points must be read at the frequency stated in the method statement
- New cracks or movement in adjacent buildings must be reported immediately to management
- Spoil heaps placed too close to structures can cause overloading and collapse
- Temporary works designs set the safe sequence and depth limits for excavation
- Low-vibration plant should be used near sensitive or fragile existing structures
Applicable Legislation: CDM Regulations 2015 · BS 5975:2019 (Temporary Works) · Health and Safety at Work etc. Act 1974 · Building Regulations 2010
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