The Frontline of DX in Exterior Wall Inspections: Safe Inspections Without Scaffolding Using Smartphone 3D Scanning

To prevent accidents caused by cracks in exterior walls or falling tiles, there have been reported cases in which passersby were injured by detached exterior tiles due to aging, and for buildings above a certain scale exterior wall inspection (exterior wall survey) is periodically required. Especially for apartment buildings and public facilities that have passed 10 years since completion, a full exterior wall survey by specialized technicians is necessary (periodic reports based on Article 12 of the Building Standards Act). Under the Building Standards Act’s periodic reporting system, for specified buildings of a certain scale used by an unspecified large number of people, a visual inspection roughly every 3 years and a detailed full sounding inspection at the 10th year after completion (and thereafter as needed) are required. However, conventional exterior wall inspections have many issues, and calls for improvement have come from the field.

• The burden of erecting scaffolding: Erecting scaffolding around the entire building requires large costs and many days, and preparations comparable to major repairs are necessary. During inspections, impacts on the scenery and daily life cannot be avoided. In practice, total exterior wall inspection costs can vary by several times depending on the inspection method, and whether expensive scaffolding is used often has a major effect on cost.

• Safety risks of high-altitude work: High-altitude sounding and visual work are always accompanied by the danger of falls and similar accidents. The burden on workers is large, and it is becoming difficult to respond amid labor shortages.

• Dependence on individual inspectors: Evaluation of exterior wall deterioration tends to rely on the human eye and is inevitably subjective. As a result, judgments can vary among multiple inspectors, and it has been difficult to quantitatively record and compare the progression of deterioration.

• Cumbersome record-keeping and reporting: Conventionally, inspectors would handwrite crack locations on wall drawings or have to organize photos afterward. Report creation was also laborious, and information sharing and accumulation did not proceed smoothly.

Owners and managers frequently ask, “Can we inspect the exterior walls more easily without erecting scaffolding for full sounding?” and “Can we conduct reliable safety inspections at lower cost?” To meet these needs, a new method that can be called the cutting edge of DX for exterior wall inspections (digital transformation) has emerged: exterior wall inspection using 3D point-cloud scanning with a smartphone. This method digitizes the entire building exterior without scaffolding and allows damage points to be checked on site with AR, and it is poised to greatly change the way exterior wall inspections are performed.

Next-generation exterior wall inspections with a smartphone: Overview of LRTK

A solution attracting attention to solve these issues is the smartphone-based exterior wall inspection system “LRTK”. LRTK attaches a small centimeter-level GNSS receiver (a palm-sized device mounted on the back of a smartphone) to the phone and uses a dedicated app to perform 3D scanning and AR display; it is designed so that anyone on site can easily carry out digital surveying. Where previously special laser scanners or artisan skills were required for three-dimensional measurement of exterior walls, it is becoming possible with just a smartphone.

The main functions enabled by LRTK are as follows.

• 3D point-cloud scanning: Using the smartphone’s LiDAR sensor or photogrammetry functions, the system scans the building exterior down to every corner and acquires three-dimensional data (point clouds) composed of numerous points. Without scaffolding or high-altitude work platforms, you can digitally record the wall shapes simply by walking around the building from the ground or its surroundings. The acquired point-cloud data are tagged with high-precision position coordinates by LRTK, allowing analysis in combination with drawings and other survey data. Since surface color information is also included in the acquired data, small cracks and stains can be visually identified in the 3D space.

• Damage verification via AR: The acquired point-cloud model can be displayed on the smartphone screen in AR on site and checked overlaid on the real building (the display remains precisely aligned with the real object even if the smartphone is moved). Viewed through the screen, the virtual 3D model is displayed in perfect alignment with the real exterior wall, enabling intuitive comparison for cracks or deformations. If the point cloud has missing areas (scan gaps), these can be immediately recognized and additional shooting can be done as needed to supplement the data.

• Geotagged photo records: Areas of concern on the wall can be photographed, and the photos are saved along with position information in 3D. Because shooting points are specified on the point cloud data, it is immediately obvious which part of the wall a photo corresponds to. You can record photos with attached XYZ coordinates and names so that anyone can accurately identify the location without handwritten notes like “crack A is near the window on the south side of floor X.” Photos can include timestamps and comments, and classification according to the type and urgency of deterioration can be performed on site.

• Cloud integration and sharing: Scanned point-cloud data and recorded photos can be uploaded to the cloud and shared with stakeholders via the internet. Using a cloud viewer, 3D point clouds and photos can be viewed from a web browser, so anyone can handle the data without specialized software. Digital data acquired on site can be viewed on office PCs, and remote technicians can review the same model and provide instructions, helping to address labor shortages. Since data are accumulated in the cloud, they can be compared with previous inspections to quantitatively understand the progression of deterioration over time, which is useful for long-term maintenance. Storing data in the cloud also eliminates concerns about data loss.

Exterior wall inspection flow using smartphone 3D scanning

Now let’s review the basic on-site flow of how smartphone exterior wall inspections with LRTK actually proceed.

• 3D scan of the entire building: First, walk around the building perimeter and scan the walls with a smartphone. If the device has LiDAR, simply holding the device and walking will sequentially capture the wall shapes and generate a point-cloud model of the entire building in a short time. During scanning, the acquired point cloud is displayed in real time on the smartphone screen, allowing you to proceed while checking that no areas are missed. If LiDAR is not available, a 3D model can still be created from photos taken from multiple angles with the smartphone camera. From the ground to the eaves, including high areas that were previously difficult to approach, the building exterior is digitally recorded without omission.

• On-site verification of scan results with AR: After scanning, switch the smartphone to AR mode to verify the results on site. The previously acquired 3D point-cloud data are overlaid on the real building, and when viewed through the smartphone screen the digital model is displayed to match the actual exterior wall. This visualizes subtle distortions or tilts in the wall that are hard to notice with the naked eye, enabling three-dimensional checks for abnormalities. If the point-cloud model has gaps, those areas will appear misaligned with the real object, making missed shots easy to detect. Additional scans can be taken as needed to supplement the data before proceeding to the next step.

• Photographic recording of damage: When deterioration such as cracks, delamination, or peeling is found on the wall, photograph the area with the smartphone to record it. When photos are taken using the LRTK app, the images are automatically tagged with the coordinates of the shooting location. For example, information like “a crack ○ mm (○ in) wide on the north-facing central area of floor ○” can be understood at a glance from the photo. Multiple photos are pinned on the point-cloud model so that deterioration spots can be listed and overviewed later in the 3D view. As needed, measurements can be made on the point cloud to quantitatively record crack lengths or delaminated areas.

• Cloud sharing and reporting: The point-cloud data and photo information acquired on site can be immediately shared with internal stakeholders via the cloud. It is easy to check the on-site 3D model in real time from the office or download data for use in reports. Reporting work, which used to involve sorting many photos and plotting them on drawings, can be streamlined with LRTK by combining point-cloud models and geotagged photos. Accumulated cloud data become valuable records for planning future exterior wall inspections.

Benefits of DX for exterior wall inspections: Improved safety, efficiency, and record-keeping

Exterior wall inspection methods using smartphone 3D scanning offer various advantages compared to conventional methods. In particular, they dramatically improve safety, work efficiency, and recording accuracy in the following ways.

• Improved safety by reducing high-altitude work: Since dismantling scaffolding and high-altitude sounding work are unnecessary, the risk of worker falls is greatly reduced. Collecting data safely from the ground makes exterior wall inspections that were once dangerous much safer to conduct. The risk of falling objects during work is also reduced, benefiting building users and neighbors. Compared to rope access or drone inspections, smartphone inspections do not require special qualifications or training and can be carried out more easily and safely.

• Reduced work time and cost savings: Eliminating the need to erect and dismantle temporary scaffolding dramatically shortens the total time required for exterior wall inspections. Large building inspections that conventionally required weeks to months from start to reporting can, with digital scanning, be completed in as little as a few days. Rapid inspections enable earlier decisions on restoration and repairs, and can produce long-term cost savings. By reducing scaffolding and labor costs, inspection costs can in some cases become a fraction of those of conventional methods. Also, there is no longer a need to cover an entire building with sheets for long periods and force residents to endure it. Reducing temporary materials also contributes to reduced waste and resource conservation, benefiting the environment.

• Dramatic improvement in recording accuracy and information sharing: Records using 3D point clouds plus geotagged photos are revolutionary in that inspection results can be stored as objective data. Without subjective variations among people, the same information can be shared by anyone, improving reproducibility and reliability of deterioration judgments. Point-cloud data allow quantitative comparisons over time, so tracking deterioration such as “the crack has advanced by X mm since the last inspection” is straightforward. Data accumulated in the cloud can be shared organization-wide, facilitating knowledge accumulation and simultaneous viewing and analysis by multiple personnel. As a precise record asset unmatched by paper reports, this contributes greatly to future maintenance and repair planning. When managing multiple buildings, centralized data management aids in objectively prioritizing repairs and optimizing resource allocation.

Implementation examples and use scenarios: DX for exterior wall inspections expanding across building types

Smartphone 3D scanning for exterior wall inspections is expected to be used across a wide range of buildings, from detached houses to high-rise towers. Below are major anticipated use scenarios.

• Detached houses: For individual homes and low-rise apartments, it can be used easily for crack checks and investigation of paint deterioration. Inspections that used to be done by visual inspection and ladders can be recorded in detail in a short time with smartphone scanning. For example, owners could scan and check their exterior walls themselves after an earthquake or typhoon. If home builders or renovation contractors introduce the technology as an after-sales service, they can enhance proposals and maintenance planning for customers. It is also useful for understanding existing conditions before exterior painting or renovations; if contractors and owners share a 3D model, it is easier to achieve a common understanding of repair scope.

• Condominiums and multi-unit housing: This is highly effective for periodic inspections by management associations and management companies. For mid- to high-rise condominiums requiring full exterior wall surveys under the Building Standards Act, DX technology offers significant benefits in terms of cost reduction and speed. Using LRTK scan data, the overall deterioration status of the building can be viewed at a glance, and the 3D model can be shared as explanatory material for residents. Inspections that were previously performed with scaffolding every 10 years can realistically be conducted on a shorter cycle as needed, enabling earlier preventive maintenance. Additionally, point-cloud data can be used to calculate exterior wall areas and tile counts, aiding rough estimates for repair work.

• Public facilities (government buildings, schools, etc.): DX for exterior wall inspections is advancing even in public buildings managed by local governments. City halls, libraries, and schools, which often face deferred inspections due to budget constraints, can use smartphone scanning for low-cost condition assessments. For example, school buildings could be quickly scanned during summer vacation to check for dangerous areas before the new term starts. 3D data can be used for presentations to councils or residents, supporting consensus-building based on objective data. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting ICT use in infrastructure inspection, accelerating adoption at the municipal level.

• High-rise buildings and special structures: For super-tall office buildings and uniquely shaped structures, inspections have traditionally relied on gondolas or drones, but smartphone 3D scanning also adds value. Even if it is difficult to photograph everything from the ground, frequently scanning lower floors and reachable areas and accumulating those data can provide useful insight into long-term trends. LRTK is also highly compatible with drone aerial photography, so a hybrid approach—using drones for high parts and smartphones for lower parts and integrating both point clouds to build a complete model—is possible. This enables safe inspections of tall buildings with minimal scaffolding.

For example, in one case, LRTK was introduced for a 30-year-old, 10-story condominium where conventional full exterior wall surveys would have required hundreds of thousands of yen for scaffolding. The management company’s technician scanned the building perimeter with a smartphone over two days and obtained high-precision point-cloud data. Sharing the data in the cloud and reviewing deterioration locations with residents and repair contractors allowed the formulation of a repair plan without erecting scaffolding. In this case, investigation costs were reduced by approximately 80%, and explanations to residents using the 3D model proceeded smoothly.

Conclusion

The smartphone 3D scanning technology that supports DX in exterior wall inspections is deeply connected with the positioning measurement technologies originally developed in the surveying field. The evolution of smartphones into high-precision surveying instruments through RTK-capable devices like LRTK has made it possible for anyone to easily obtain building 3D models. The affinity between such surveying technology and exterior wall inspection work is high, and deterioration diagnosis based on precise point-cloud data is excellent in terms of reliability and reproducibility. Furthermore, because inspection results remain as digital data, creating reports for administrative submission and securing evidence of legal compliance becomes easier. Once acquired, a building’s point-cloud data can also be used for other purposes—for example, quantity calculations for exterior repairs or as a base for renovation design by importing into BIM software—functioning as a form of simple 3D surveying. In other words, LRTK bridges the previously separated fields of “inspection” and “surveying/design,” promoting cross-functional DX.

The benefits that such digital technology brings to exterior wall inspections, which were traditionally accompanied by danger, are immeasurable. By transforming work that relied on skilled intuition into data-driven processes, it reduces dependence on individual expertise and enables everyone to evaluate building safety by the same standards. Accumulating inspection results also supports a shift to preventive maintenance, contributing to longer building lifespans and preservation of asset value. While further technological advances such as AI-based automatic crack detection and integration with drones and robots are expected, it is important to take the first step toward DX using the smartphone in your hand. Companies that have adopted this technology report tangible effects such as “work has become significantly faster” and “resident explanations are smoother thanks to shared data.” There are also evaluations like “we can now make objective judgments without relying on veteran intuition,” indicating a positive response to DX. Embrace smartphone 3D scanning technology—the frontline of DX in exterior wall inspections—and take a new step in managing your buildings.