3D Laser Scanning for Building Restoration After a Disaster
After a fire, a flood, a storm or a collapse, a building has to be documented twice: as it is on the morning after, for the insurer, the engineer and the authority, and as it was, for the building restoration that follows. The second record often does not exist, and the first has to be made before anything is cleared, propped or demolished. This guide explains how 3D laser scanning records a damaged building, what the scan captures and what it cannot in a structure that is unsafe to enter, how the record is used by the people who have to decide what happens next, and how it becomes the base for the restoration.
The record on the morning after
A damaged building changes by the hour. Water drains, charred timber can dry and move, a leaning wall is shored or comes down. A laser scan taken before the site is touched records what stands in the scanner’s line of sight as it is that day: the lean of a wall, the sag of a floor, the line where the water stood, the opening a collapse left. By its datasheet, a scanner of the Trimble X7 class holds a 3D point accuracy of 2.4 mm at 10 m, 3.5 mm at 20 m and 6.0 mm at 40 m (one standard deviation) over a range that reaches 80 m, which is what allows a building that cannot be entered to be scanned from the street and the neighboring lots, and from the roofs around it where access is granted, with the scanner no closer than the engineer or the authority permits.
The scan is scheduled as soon as the project needs it, often within days of the order, so that the record exists before the clearance begins.
What the scan captures and what it cannot
From outside, the scan records the envelope: the facades, the roof where it can be seen from adjacent height, the openings, the damage visible from the street and the condition of the adjoining buildings, which an insurer for a neighboring property may want as much as the owner does. From inside, where entry is permitted, it records the rooms, the floors, the ceilings and the structure exposed by the damage, with the scanner on a tripod and the operator in the building for a few minutes per station.
What the scanner cannot see is not in the cloud. A collapsed floor hides the one below it; a smoke-blackened room may need the high sensitivity mode the datasheet lists for dark surfaces, which takes about twice as long for the same point spacing; standing water returns little of the beam; and the structure behind a finish is not captured until the finish is off. The scan records surfaces, and the engineer’s assessment of what is behind them, the condition of the steel after a fire or of the reinforcement after a flood, is the engineer’s work, informed by the geometry the scan gives.
How the record is used
The registered point cloud, delivered in E57, the ASTM exchange format for 3D imaging data, and in RCP/RCS for Revit with its registration report, is the measured record that the insurer, the structural engineer and the authority can each open and measure in. An engineer measures the lean of a wall or the deflection of a beam directly in the cloud, against the surveyor’s control when the project has it; an adjuster compares the building with the record set and with the pre-loss photographs; an authority deciding about the structure has its measured geometry in front of it. The panoramic images from each scan position, delivered with the cloud when the stations were photographed, show what the points do not: the texture of a charred surface, the label on a panel, the contents of a room on that day.
When the building has to be shored or partly taken down before the engineer can enter, the scan can be repeated after each stage when the scope includes it, so that the record follows the building through the clearance.
The base for the restoration
A restoration is designed against the building as it stands after the damage, and that is the second use of the scan. As-built drawings are traced from the cloud: plans, elevations and sections in DWG and PDF, with the sheet saying which lines were measured and which were taken from older documents. A Revit model of the surviving structure is built from the same cloud when the design is done in Revit, at the level of development the scope names, with the destroyed elements carried from the pre-loss drawings where those exist and marked as unverified. The quote states the accuracy of the drawings and the model as a USIBD Level of Accuracy, a standard deviation at the 95 percent confidence level; LOA30, which allows a deviation of 15 mm down to 5 mm, is the usual level for a set of this kind. For a historic building, the scan of what survives is also the record of the ornament and the profiles that the restoration has to reproduce; the guide to 3D scanning for historic preservation covers that case.
The 3D laser scanning, as-built drawings and Scan-to-BIM pages describe each deliverable.
Price and time
A damaged building is priced on what can be reached and what is built on the cloud, and the ranges are the same typical ranges as for any building: the point cloud alone starts at about $1,200; a house or an apartment with drawings or a model, $2,000 to $4,500; interiors with the facades and the site, $2,500 to $5,000; an office or a commercial floor, $3,000 to $9,000; large buildings run from $12,000 and are quoted on their own. A building scanned only from outside, or in stages through a clearance, is quoted on its own. The exact price comes in a quote within one business day of your sending the address, photographs and what the record is for, and the scan is scheduled as soon as the project needs it. The cloud and its report usually arrive a few days after the scan; drawings and models have their own dates in the quote. We scan in all 50 states.
FAQ
Can you scan a building that is unsafe to enter?
From outside, yes: the facades, the roof where it can be seen, the openings and the visible damage are scanned from the street and the surrounding lots, with the scanner no closer than the engineer or the authority permits. Interiors are scanned where entry is permitted.
How soon after the loss can the scan be done?
It is scheduled as soon as the project needs it, often within days of the order. The record has to be made before the site is cleared, shored or demolished.
What does the insurer get?
The registered point cloud with its registration report and the panoramic images from each scan position, in formats that open in point cloud software in general, so the damage can be measured in the file.
Can you show what the building looked like before the loss?
Only from the records that exist: older drawings, photographs or a scan taken earlier. A scan after the loss records the building as it stands that day, and the model carries the destroyed elements from the pre-loss documents, marked as unverified.
Is the scan a structural assessment?
No. The scan records the geometry: the lean of a wall, the deflection of a floor, the extent of a collapse. The assessment of the structure’s condition is the engineer’s work, on that measured base.
How much does it cost?
The same typical ranges as for any building: the point cloud alone from about $1,200, a house with drawings or a model $2,000 to $4,500. An outside-only or staged scan is quoted on its own. The quote arrives within one business day.
Sources
- Trimble X7 3D laser scanning system datasheet: range, scan speed, 3D point accuracy at 10, 20 and 40 m, station durations, high sensitivity mode.
- ASTM E2807, Standard Specification for 3D Imaging Data Exchange: the E57 file format.
- Autodesk Revit help: linked point clouds require indexed RCP or RCS files
- USIBD Document C120, Level of Accuracy Specification Guide, version 2.0 (2016): the LOA levels as standard deviations at the 95 percent confidence level.
