Disputes with adjacent buildings are among the most expensive risks of urban construction, because they can stop work immediately even when the actual damage is small. The root cause is usually not proving who is at fault, but that nobody has evidence of what the building looked like before work started. This article summarizes what to record, how to make a crack map and install monitoring instruments, how far out to survey, and what kind of report actually holds up in negotiations.

High-rise construction project in Bangkok with adjacent buildings on the property line
Urban construction with adjacent buildings right up against the property line — in conditions like this, the condition of surrounding buildings should be recorded before machinery enters the site

What is a dilapidation survey, and when is it done?

A dilapidation survey is the inspection and recording of the existing damage to adjacent buildings as evidence, before starting construction activities that may cause vibration or ground movement. In Thailand it is often called an "adjacent building condition survey" or a "pre-piling condition inspection" — they are the same job.

The right time is before heavy machinery enters the site, not after two or three piles have already been driven, because evidence collected after work has started can immediately be challenged on the grounds that the cracks may have been caused by the early works.

Five groups of activities should always be preceded by a survey, because they can move the surrounding ground even with good site control:

  • Pile driving
  • Large-diameter bored piling
  • Deep excavation and retaining wall works
  • Building demolition
  • Works requiring groundwater lowering (dewatering)
Aerial view of prestressed concrete pile driving, showing rows of driven pile heads and piles stacked at the edge of the site
Pile driving puts the most energy into the ground in the early phase of a project — the condition survey of adjacent buildings must be completed before the first pile goes in (Photo: SPN Soil Engineering)
Aerial view of excavation and pile head cutting for foundations, with a steep excavated face at the edge of the site and an excavator working above
Deep excavation loosens the adjacent soil and lets it move toward the excavation; even without vibration, surrounding buildings can undergo differential settlement
Aerial view of a construction site with many pile heads cut and foundations being prepared, with a building under construction at the edge of the site
On sites with dense foundation work and buildings right on the boundary, survey points and instrument locations should be set from the planning stage
Engineers and technicians walking through foundation work with lean concrete placed, with a crane and the project's steel structure in the background
A joint site walk-through by the team shows which phases of work will come close to the property line and where monitoring of adjacent buildings should be stepped up

Why do it when the law does not directly require it?

Because when a claim arises, the party without evidence of the prior condition can hardly tell which cracks are old and which are new. Legally, liability for construction that damages another person's property falls under tort law in Section 420 of the Thai Civil and Commercial Code, under which the injured party must prove that damage actually occurred and was caused by the other party's actions.

In practice, however, when cracks appear in a neighboring house while piles are being driven right outside, everyone's opinion immediately leans the same way. The usual result is a work stoppage for negotiations, and a payment to get work moving again.

💡 The real value of this documentation

An adjacent building survey report does not prevent damage, but it makes the scope of liability clear. The construction side is liable only for what actually got worse, and the owner of the adjacent building is compensated for the damage that actually occurred — which is why negotiations end much faster than arguing on feelings.

What must an adjacent building survey report record?

A usable report must answer 3 questions: which building was surveyed, what its condition was on that day, and when it was surveyed. The required elements can be summarized in 7 items, as shown in the table.

← Scroll to see the full table →

TopicWhat to record
Building informationAddress, owner or occupant, number of stories, structural system as far as can be observed, distance from the construction line
PhotographsOverall views of all 4 sides, close-ups of every crack with a ruler or scale in the frame, and the date embedded in the image file
Walk-through videoContinuous, unedited footage walking around the building and through accessible rooms, confirming that the record is not limited to hand-picked spots
Crack location plan (Crack Map)Location, direction, length and width of each crack, with reference numbers matching the photographs
Tilt and settlementPlumbness of walls or columns, floor level differences, gaps between floor and wall, doors and windows that do not close properly
Services and building elementsCracked tiles, leaks, water pipes and gutters with existing defects, fences and walkways around the building
Sign-offSurvey date, name and signature of the surveyor and, where possible, a joint acknowledgment signed by the owner of the adjacent building

The last item is often overlooked. Having the adjacent building owner sign an acknowledgment of the survey turns the report from "a document the contractor made on its own" into "a document both parties are aware of" — which carries very different weight at the negotiating table.

How are a crack map and crack gauges done?

A crack map is a plan showing the location and size of every crack in the building on the survey date, while a crack gauge is an instrument fixed across a crack to read changes in its width over time. The first answers "what was there on that day"; the second answers "is that crack still moving". These are different questions, and the two must be used together.

A practical way to make a crack map is to write a reference number next to each crack on the wall in pencil or with a sticker, photograph it so that the number and a measuring scale are in the same frame, and then record the width with a crack width gauge card. Numbering the cracks makes it possible to re-photograph exactly the same spot in the next round.

A plate-type (tell-tale) crack gauge is fixed to the wall on both sides of the crack, and the movement of its scale is read at set intervals, e.g. weekly during pile driving. A steady reading means an old crack that has stopped moving; a continuously increasing reading is a signal that the project's responsible engineer must be notified immediately.

Monitoring cracks in an adjacent building with a plate-type (tell-tale) crack gauge, and reading the trend of readings during pile driving The left panel shows the wall of an adjacent building with crack number C-01 and a two-layer tell-tale crack gauge fixed across it. The lower plate carries a millimeter grid and is fixed to the left side of the crack; the clear upper plate carries a crosshair and is fixed to the right side. When the crack moves, the crosshair moves over the grid, so two directions can be read: opening along X and shear along Y. A baseline reading must be taken before machinery enters the site, then repeated at about the same time of day each round. The right panel is a conceptual graph of the change in width relative to the baseline over time, divided into before work, during pile driving and after completion. The green line fluctuates slightly around the original value with temperature, meaning the crack has stopped moving. The red line rises steadily until it reaches the alert threshold set in advance by the engineer, and the responsible engineer must be notified immediately. The bottom strip summarizes the three layers of monitoring: vibration indicates the level of loading, the crack gauge indicates the building's response, and settlement points or inclinometers show how much the ground and structure have moved. Crack gauge: is the adjacent crack still moving? Not to scale Fixed across crack C-01 on adjacent wall C-01 1 2 3 X Y ① Lower plate: mm grid, fixed left of crack ② Clear top plate: crosshair, right side ③ Read 2 axes: opening (X), shear (Y) Baseline reading before machinery arrives Reading trend (conceptual) Before work Pile driving After work Alert level 0 Time Δ width (mm) → Hits limit → Notify engineer Fluctuates = crack has stopped Small thermal swings are normal, so read at the same time of day 1 Vibration (PPV) Level of loading 2 Crack Gauge Building response 3 Settlement Point Ground + bldg movement
Crack monitoring principle — a tell-tale only measures the change in distance between the two sides of a crack relative to the baseline reading, not the absolute crack width. A reading that fluctuates slightly around the original value is a crack that has stopped moving, while a reading that climbs steadily until it reaches the threshold set in advance by the engineer is the point at which the project's responsible party must be notified.

How far out should buildings be surveyed?

There is no single radius that works for every project. The extent depends on the type of activity, the energy put into the ground, the depth of excavation, the local soil layers, and the vulnerability of the adjacent buildings themselves. Old buildings on shallow foundations on soft soil are affected at greater distances than new buildings on deep piles.

The approach used in practice is to start with every building on the property line, then extend coverage to buildings within approximately 30–50 meters of the pile driving line or the excavation edge, and then adjust the extent to actual conditions — for example, an old or heritage building further away should also be included.

3D model of the survey extent for adjacent buildings around a construction site, and monitoring instrument locations during pile driving (conceptual) Conceptual 3D view of a construction site with a pile-driving rig in the center, standing on a cut-away soil block that shows a soft soil layer and piles already driven, surrounded by four adjacent buildings. The two-story shophouse on the left sits on the property line and belongs to the group where every building must be surveyed. On its wall facing the construction there is a crack labeled C-01 with a crack gauge fixed across it, and a tilt meter mounted on the wall. At the foot of the wall a vibration monitor sits on the ground, and there is a settlement point at the building corner. In the soil section between the building and the works an inclinometer casing is installed in the ground, and dotted arcs show vibration waves radiating from the pile toward the building. A blue dashed line on the ground marks a distance of approximately 30 to 50 meters from the works, covering the four-story building at the back and the single-story house on the right. The old timber house on the far left lies outside the dashed line but is included because it is an old, vulnerable building. A surveyor stands photographing the building wall. The box on the right splits the items into two groups: before work, consisting of photos and video of all four sides and a crack map with reference numbers; and during construction, consisting of crack gauges, vibration measurement, settlement points with tilt meters, and inclinometers at the excavation edge. The bottom strip summarizes the three steps for setting the extent: every building on the property line, buildings within approximately 30 to 50 meters, and old or vulnerable buildings further away. The actual distance must be set by the project engineer. 3D model: which buildings to survey, where to monitor Not to scale 1 2 3 4 5 5 6 Construction site Piling · excavation · demolition On property line Survey all Old / vulnerable bldg Include even if out of range ~30–50 m from the works Starting point for extent Vibration waves + ground movement Before work · record condition 1 Photos + video, 4 sides Dated · scale in frame 2 Crack Map Crack number, e.g. C-01 During works · monitoring 3 Crack Gauge Is the old crack moving? 4 Vibration monitoring (PPV) Level of loading 5 Settlement pts + tiltmeter How much bldg settles/tilts 6 Inclinometer Ground movement at excav. 1 On property line Survey all 2 ~30–50 m from piling line / excav. edge 3 Old · vulnerable bldgs Include even if farther Conceptual · positions and distances are assumed Actual extent and alert levels set by the project engineer
Conceptual 3D view — the extent starts with every building on the property line, extends to approximately 30–50 meters, and includes vulnerable old buildings even if they are farther away. Numbers 1–6 are the items recorded before work and the instruments used for monitoring during construction. Distances and positions in the figure are assumed values.
SPN staff surveying a construction site with an old timber house on the property line
Old buildings on shallow foundations along the property line always come first on the survey list, because they respond more to vibration and ground movement than new buildings (Photo from an SPN subsurface investigation job)
Survey work on an inner-city construction site surrounded by high-rise and commercial buildings
Inner-city construction sites have both high-rise and low-rise buildings all around, so the survey extent has to be worked out building by building based on distance and vulnerability, not with one radius covering everything
⚠️ The extent must come from the project engineer

The distances above are only a starting point for planning, not a criterion that replaces project-specific assessment. The actual survey extent should be set by the responsible engineer, taking into account the soil profile from the project's soil investigation report.

What else must be monitored during construction?

During construction, 3 additional layers must be monitored: crack gauge readings, vibration, and movement of the ground and structures, because the pre-construction survey is only the first reference point.

  • Read crack gauges at set intervals — keep a log of dates and readings, with photographs every time, so the trend is visible rather than just the final value.
  • Vibration monitoring — measure peak particle velocity at adjacent buildings during pile driving to check whether vibration levels are within the reference criteria. For measurement methods and reference criteria such as DIN 4150-3 and BS 7385-2, see Pile Driving Cracked the House Next Door? Vibration Monitoring
  • Monitor ground and structural movement — for deep excavations or retaining wall works, install instruments such as settlement points or inclinometers; see the Geotechnical Instrumentation page for guidance. To turn settlement and tilt of adjacent buildings into numbers that can be compared with alert levels, read how to select and place measurement points in Settlement Points and Tiltmeters: Measuring Settlement and Tilt of Adjacent Buildings
SPN staff surveying in the narrow gap between an adjacent building and the site fence
The narrow gap between an adjacent building and the site boundary is the hardest place to access, but it is exactly where both pre-construction photos and monitoring rounds during construction are needed (Photo: SPN Soil Engineering)

These three layers complement each other. Vibration readings tell you "how strong the loading is", crack gauge readings tell you "how the building is responding", and movement instruments tell you "how far the ground and structure have moved". Having all three makes it possible to explain events in sequence instead of guessing after the fact.

How is this documentation used when a dispute arises?

As "before–after" comparison images of the same spot, to separate existing cracks from new ones. The steps that resolve the matter quickly almost always follow the same sequence:

  1. Respond and visit the site immediately — look at the location of the complaint first; do not deny before looking.
  2. Open the original survey report — compare photographs of the same spot by crack number.
  3. Record the current condition — take a new set of photographs and width measurements that day.
  4. Agree on the findings together — if it is an existing crack, show the dated comparison images directly to the building owner. If it is a new crack or an existing crack that has widened, have an engineer assess whether it affects structural stability or is only cosmetic damage, and then decide on the repair approach and who is responsible.

Where cracks are in worrying locations such as columns, beams or load-bearing walls, further in-depth non-destructive testing should be carried out to see whether the concrete and reinforcement are affected. For suitable methods in this case, see the NDT guide for non-destructive testing of concrete structures, and if the adjacent building is an old building with pre-existing problems, read the assessment approach in Before Extending an Old Building: What Structural Checks Are Needed

✅ What gives a report weight

Photographs with the date embedded in the file · a measuring scale visible in close-ups · crack reference numbers that match between the map and the photos · the surveyor's signature · and, where possible, an acknowledgment signed by the owner of the adjacent building. These elements make the document much harder to challenge.

Summary

Surveying adjacent buildings before construction is low-cost paperwork compared with the risk it prevents. The key is to do it before real work starts, photograph every side, make a crack map with reference numbers, and install instruments at locations of concern to see the trend along the way.

When a claim comes in, what settles it is not insisting that "we did the work correctly", but comparison images that both parties look at and agree on what has changed. Vibration monitoring alongside helps show that construction really stayed within controlled levels. To plan a survey and instrumentation for your project, contact us for a free quotation within 24 hours.

⚠️ This article provides general information

This content summarizes practice for general understanding only. It is not legal advice and not a project-specific plan. The survey extent, vibration control criteria and damage assessment must be set by the project's responsible engineer, and questions of liability and damage claims should be discussed with your legal advisor.