Vibration monitoring, and the neighbour dispute it prevents

Vibration monitoring, and the neighbour dispute it prevents

On a tight Sydney site, the work that creates the most risk to a builder is not the work on the site. It is what the neighbours say about it afterwards.

Rock breaking, piling, sheet piling, compaction and demolition all transmit energy through the ground into adjacent buildings. Whether that energy caused damage is a technical question, and without data it becomes an argument nobody can win.

What vibration actually does to a building

Buildings tolerate more vibration than people assume, and people tolerate far less than buildings do.

The level at which someone inside a house becomes alarmed is well below the level at which anything is damaged. That gap is the source of most disputes, because the complaint is genuine and the damage claim that follows it is often pre-existing.

Damage risk is assessed against peak particle velocity, and the thresholds vary by the type and condition of the structure. A modern reinforced concrete building tolerates far more than an unreinforced masonry cottage or a heritage listed building with lime mortar.

Monitoring is a record, not a control

A vibration monitor sits on or in the adjacent structure and records continuously through the works, logging the level, the frequency and the time of every event.

That produces two things. A live alarm when a level approaches the limit, so the method can be changed before anything is damaged. And a complete record afterwards, timestamped, showing exactly what the building experienced.

When a claim arrives six months later, that record is the evidence. Without it, the discussion is one person's recollection against another's.

Dilapidation surveys are the other half

Monitoring tells you what happened during the works. A dilapidation survey tells you what the building looked like before them.

Together they answer the whole question. Separately, neither does. A monitoring record showing low levels is useful, and it is far more useful alongside photographs proving the crack was already there.

Both are done before work starts, and access to the neighbouring property has to be arranged, which takes longer than people plan for.

What triggers the need for it

Rock excavation, which in much of Sydney means hammering sandstone within metres of a boundary.

Piling, particularly driven piles. Bored and screw piles transmit far less, which is sometimes the reason to choose them.

Demolition, especially where a party wall or a shared boundary is involved.

Compaction, which people underestimate because the plant is small and the frequencies it generates couple well into nearby structures.

Proximity to anything sensitive: heritage buildings, buildings with existing damage, hospitals, laboratories, or a neighbour who has already engaged a solicitor.

Setting the limits

Limits are set from the standards, adjusted for the condition and type of the adjacent structure, and often written into the conditions of consent.

Where a heritage building is involved the limit is usually lower, and the method statement has to be built around achieving it rather than tested against it afterwards.

The commercial case

Monitoring costs a fraction of one contested claim. It also gives a builder the ability to keep working when a complaint arrives, because the answer is available immediately rather than after an investigation.

We set up monitoring, limits and dilapidation records as part of project management and geotechnical work on constrained sites, and it is the cheapest risk reduction available on an urban excavation.