The most common dispute between project owners and neighbors in foundation work is over cracks that appear during pile driving. One side insists the house never cracked before; the other insists the piles were driven to standard. Almost every time, neither side has any numerical data to back up what they say. Vibration monitoring and a pre-construction (condition) survey are therefore the two tools that turn an argument based on feelings into verifiable data.
Can pile driving really crack the house next door?
Yes, it can, but you need to draw a clear line between "feeling vibration" and "damage severe enough to crack", which are very different levels. Research and international criteria on building vibration agree that humans are very sensitive sensors. Under the British guidance BS 5228-2, occupants of residential buildings begin to perceive vibration at a particle velocity of about 0.3 mm/s (in the most sensitive conditions perhaps from about 0.14), are likely to start complaining at about 1 mm/s if they have not been notified in advance, and at 10 mm/s most people find it intolerable even for short periods. By contrast, the level at which plastered walls start to develop small cosmetic cracks in ordinary residential buildings is about 5–20 mm/s under the commonly used reference criteria.
The level at which people start complaining is therefore about 5–20 times lower than the wall-cracking threshold, and the level at which they first feel vibration is lower still. On most sites this means neighbors clearly feel the vibration and become very worried, even though the measured values are still far from the damage threshold. Conversely, there are cases where actual values exceed the limit and nobody notices, because human perception also depends on frequency and exposure time, not on intensity alone. Judging by feel is therefore unreliable in both directions.
Factors that make pile-driving vibration more or less severe from site to site include the driving energy and hammer weight, the pile system chosen, the stiffness of the soil layers the pile toe must penetrate, the depth of the dense sand layer, the distance to neighboring buildings and, often overlooked, the existing condition of the neighboring building itself. Old buildings with accumulated cracks, unreinforced masonry without tie columns and lintels, or shallow foundations on fill are more sensitive to vibration than reinforced concrete buildings supported on piles. If you are unsure how the different pile systems compare, read more in Pile Types Compared
What is vibration measured with, and how are the readings interpreted?
The main instrument is a geophone, a triaxial particle-velocity sensor fixed firmly to the floor or foundation of the building being monitored and connected to a recorder that logs the signal continuously throughout the work. The main reported value is PPV (Peak Particle Velocity), the maximum velocity at which ground particles move, in millimeters per second (mm/s), measured simultaneously on three axes: radial, transverse and vertical.
PPV must always be read together with the dominant frequency, in hertz, because damage criteria are not a single number but are tied to frequency. Every building has its own natural frequency. If the frequency of the incoming waves is close to the building's natural frequency, the response is amplified and damage can occur at a lower PPV than usual. For this reason, international criteria allow higher PPV values at higher frequencies, because high-frequency vibration causes less relative displacement within the structure.
In addition, on work near heritage buildings or particularly sensitive buildings, monitoring is often supplemented with instruments that report continuously and have an alarm system. When a measured value exceeds an alert level set below the damage threshold, the site supervisor can change the working method immediately, before values reach the actual limit. This is the same concept used in monitoring ground and structural movement with instruments in Instrumentation work, which also uses a three-level trigger system.
The images below simulate on-site vibration monitoring as a 2D section and a 3D model, from the pile-driving point, through the waves spreading through the soil, to the geophone mounted on the neighboring house's foundation and the multi-level control values set below the damage threshold.
What vibration level counts as dangerous?
Thailand has the National Environment Board Notification No. 37 (B.E. 2553 (2010)) on Vibration Standards to Prevent Impacts on Buildings, which sets peak particle velocity limits by building type and frequency range, with measurement methods prescribed by the Pollution Control Department. It is not part of the building control law, however. In practice, project specifications, environmental impact assessment reports and construction contracts for large projects therefore often cite both this notification and foreign criteria, most commonly Germany's DIN 4150-3, followed by the UK's BS 7385-2, with ISO 4866 used as guidance on measurement and evaluation methods. The table below summarizes the value ranges from the DIN 4150-3 guidance, which are measured at the building foundation and vary with frequency.
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| Building type | Recommended PPV range | Remarks |
|---|---|---|
| Commercial / industrial buildings, robust structures | Approx. 20–50 | Lower values apply at low frequencies (about 1–10 Hz), higher values at high frequencies |
| Ordinary residential buildings | Approx. 5–20 | The most common group in urban pile driving |
| Heritage buildings / particularly vibration-sensitive buildings | Approx. 3–10 | Historic monuments, very old buildings, buildings with sensitive equipment |
| Level at which people perceive and start to complain (for comparison) | Approx. 0.3 (perceived) – 1 (complaints) | Not a damage criterion; a human-perception level per BS 5228-2 |
An important point is that the values are shown as ranges, because the actual limits in the standards vary with the dominant frequency. Taking a single number without looking at frequency can therefore be wrong in either direction. These values are also limits to prevent structural damage, not limits for occupant annoyance, which is a separate matter and uses much lower values.
DIN 4150-3, BS 7385-2 and BS 5228-2 are foreign standards used only as reference guidance. The Thai criterion is the National Environment Board Notification No. 37 (B.E. 2553 (2010)). Before using any figure, check the values in the full notification from the relevant agency. Which criterion applies to a given project must be stated in the project specification or contract and should be set by the project's responsible engineer, taking the actual condition of neighboring buildings into account.
Why does a pre-construction survey matter more than you think?
A condition survey of neighboring buildings before work starts is a systematic record of the condition of the surrounding buildings before a single machine enters the site. It costs little but is the strongest evidence when a dispute arises, because without a record of the pre-work condition there is no way to prove whether the cracks seen now were already there or have just appeared. (Read the full procedure in Adjacent Building Survey Before Construction (Dilapidation Survey))
A pre-construction condition survey report should include:
- Photographs of every crack with a reference scale and date, both inside and outside the building, including fences, parking-area pavement and visible building services
- Crack-width measurements with a crack-width ruler, with the crack tips marked so that any extension can be checked later
- A crack location plan that clearly identifies rooms and walls, so the same points can be re-inspected
- Crack-movement gauges (crack gauges or tell-tales) installed at points of particular concern
- Settlement points and tiltmeters on the neighboring building's structure, for work that also involves deep excavation or groundwater lowering
- An acknowledgment record signed jointly by the project owner and the owner of the neighboring building
When the work is finished, a repeat survey in the same format (post-construction survey) should be carried out for point-by-point comparison. Having before and after photos taken from the same angles lets negotiations conclude far faster than arguing from memory.
What does the on-site monitoring procedure look like?
On a typical project, vibration monitoring usually proceeds as follows. First, survey the neighboring buildings to select monitoring locations, choosing the nearest building and the most sensitive building, which need not be the same one. Then set three control levels — alert, action and stop-work — below the damage threshold stated in the specification.
Next, install the sensors fixed firmly to the floor or foundation in the specified orientation; a loose installation or placement on soft ground gives badly wrong values. Then record continuously throughout pile driving or other vibration-generating work, while logging site activities with matching timestamps so that each peak can be traced to the activity that caused it. Finally, compile daily or weekly reports with plots of the values against the limits, signed off by an engineer.
A common mistake is installing the monitor where it is convenient rather than where it represents the actual building, for example placing it on a road surface instead of fixing it to the building foundation, or measuring only during light work. The report then passes the criteria but does not reflect actual conditions, and data collected this way is useless when it is needed to respond to complaints.
How can vibration be reduced?
When measured values approach the limit, vibration-reduction methods used in practice range from adjusting the working method to changing the foundation system:
- Change the pile system from driven piles to bored piles or hydraulically jacked (press-in) piles. This reduces vibration the most, but you must accept the different cost and schedule.
- Pre-boring before driving reduces the energy needed to drive through stiff upper soil layers, and so reduces the vibration transmitted sideways.
- Adjust the driving energy by lowering the hammer drop height and increasing the number of blows instead of a few heavy blows. Take care that this does not conflict with the set (termination) criteria specified by the engineer. Read more about set criteria in Last 10 Blows vs Blow Count
- Dig a cut-off trench between the driving point and the neighboring building. This partly reduces surface waves, but its effectiveness depends on the trench depth relative to the wavelength.
- Sequence the work to start from the side nearest the neighboring building and move away from it, and agree working hours with neighbors in advance, reducing both impacts and complaints.
All of the methods above are changes that affect pile load capacity, so the decision must be made by the design engineer and the site supervisor, not adjusted on site for convenience. After the working method is changed, pile integrity and load capacity must still be tested as planned. For an overview of test methods, see The Complete Guide to Pile Testing Methods
How do vibration cracks differ from settlement cracks?
Not every crack that appears during construction is caused by vibration. A more common and more serious cause is ground settlement, resulting from excavation, groundwater lowering or soil movement around boreholes. Distinguishing the two causes matters because the remedies are completely different.
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| Issue | Vibration cracks | Settlement cracks |
|---|---|---|
| When they appear | Appear during or immediately after vibration-generating activity | Develop gradually and keep widening over weeks or months |
| Crack pattern | Usually hairline cracks in the plaster, distributed along material joints | Usually diagonal at about 45 degrees, wide at one end and tapering at the other |
| Growth | Stop growing once the vibration-generating work ends | Keep growing even after work stops |
| Associated symptoms | Usually no symptoms other than surface cracks | Sticking doors and windows, tilting floors, drains changing flow direction |
| What to check further | PPV records compared with when the cracks appeared | Settlement level survey; inspect foundation and soil conditions |
If the symptoms match the right-hand column more closely, the issue may not end with reducing vibration. Read about the warning signs to watch for in 5 Warning Signs of House Foundation Problems and how to read and monitor cracks in Which Structural Cracks Are Dangerous? For old buildings with no records of the existing foundation, a structural condition inspection before deciding on repairs is a step that cannot be skipped.
Who should do the monitoring, and who should you talk to first?
Vibration monitoring should be done by someone with calibrated instruments and an engineer who takes responsibility for the results, because reports without calibration data and without a signatory are easily challenged once the matter reaches the stage of negotiating compensation.
For project owners planning foundation work next to closely spaced neighboring buildings, the first thing to get right is accurate subsoil data, because it determines which pile system to choose and how much driving energy will be needed. This should be followed by a condition survey of neighboring buildings before work starts, and a plan to monitor ground movement and settlement alongside vibration measurements.
SPN Soil Engineering currently provides soil investigation, soil and pile testing, structural inspection, and installation of instruments for monitoring settlement and ground movement (Instrumentation). Dedicated vibration monitoring is not yet part of our service list. If you need to plan the overall monitoring of neighboring buildings, you can consult our engineering team for guidance.
This content explains the principles of vibration monitoring for general understanding only. The criteria actually used, the monitor locations and the damage assessment of each building must be determined directly by the engineer responsible for that project, and this does not constitute legal advice.