The importance and challenges of exterior wall inspections Building exteriors are constantly exposed to rain, wind, and sunlight, making aging and deterioration unavoidable. If issues such as detached or falling exterior tiles, mortar cracks, or deterioration and peeling of paint films are left unaddressed, they affect not only appearance but also safety. For example, there have been past incidents in which aging mortar cladding fell from a building and struck passersby. The cause was a long period without inspection, during which cracks in the exterior and corrosion of internal metal members progressed. Regular exterior wall inspections are therefore indispensable to prevent such accidents.

However, conventional exterior wall inspections have relied mainly on visual checks by certified personnel and sounding tests (tapping with a hammer to detect delamination or voids). High-altitude inspections require erecting scaffolding or using aerial work platforms, which involves significant time and cost and carries the hazards associated with working at height. Moreover, visual-centric investigations are easily influenced by the inspector’s subjectivity, making it likely that small deterioration will be overlooked or records will be incomplete. In recent years, the aging and shortage of experienced wall inspection technicians has become more serious, making it challenging to build a system that can perform inspections efficiently. Methods that mark damage locations by hand on paper drawings make it difficult to record exact positions and dimensions, and make quantitative later analysis or tracking of deterioration over time difficult.

Next-generation exterior wall inspections opened up by 3D scanning × AR To address these challenges, digital inspections using 3D scanning technology and AR (augmented reality) have drawn attention in recent years. Laser scanners, drone aerial imaging, and even smartphone LiDAR or photogrammetry can convert the building exterior into three-dimensional data without omission. If the entire wall surface is recorded as dense point cloud data (a collection of countless measured points acquired by 3D scanning), it becomes possible to accurately capture crack lengths and subtle bulging of the exterior. Because the data can be stored in the cloud and analyzed later in detail, inspections become more objective and reproducible compared with conventional visual checks. The use of 3D scanning is positioned as a foundational technology for the future in the DX (digital transformation) of infrastructure maintenance promoted by the Ministry of Land, Infrastructure, Transport and Tourism.

Furthermore, combining this 3D data with AR drastically transforms on-site exterior inspections. Using AR technology, digital information can be overlaid on the real building via a tablet or smartphone screen. For example, if a pre-acquired 3D model of the exterior is aligned with the actual structure on site, degraded areas can be intuitively identified without missing them. It is also easy to mark crack locations on AR in real time for recording, or to display drawing information in AR to navigate inspection targets. Because high-precision models obtained by 3D scanning are available, AR overlays do not misalign and can match the real object precisely, enabling highly reliable inspection assistance.

Main benefits of introducing 3D scanning × AR Below are five main benefits.

• Dramatic improvement in inspection accuracy: Digital scanning enables precise measurements at millimeter-to-centimeter scale, allowing detection on the data of minute cracks and subtle deformations of the exterior that the human eye might miss. Degradation levels that used to depend on intuition can now be quantitatively evaluated on 3D data—for example, accurately measuring crack lengths or checking the degree of tile detachment in cross-section. Because inspection results are less variable and anyone can make judgments based on the same objective data, diagnostic reliability improves.

• Significant reduction in work time: 3D scanning can measure wide exterior surfaces collectively in a short time, greatly compressing survey time compared with meticulous manual inspection. Whether using dedicated equipment or smartphone-based scanning, data acquisition can be completed simply by walking around the building. In practice, for a building about 30 m wide and 10 m high, LRTK exterior point cloud scanning can be completed in about 15 minutes. Reducing the frequency of erecting scaffolding to inspect details also cuts preparation and cleanup effort. For property management companies overseeing multiple buildings, the number of inspections possible per day increases and operational efficiency rises dramatically. In extreme cases, tasks that previously required 3–4 people a full day have reportedly been completed by one person in half a day using LRTK.

• Improved safety: Introducing scanning technology reduces the need for inspectors to work at height for long periods. Combined with drones or high-zoom cameras, dangerous areas can be investigated remotely, and only locations requiring close-up inspection need to be examined later, minimizing the risk of high-altitude work for personnel. With digital data enabling precise repair planning, urgent repairs can be addressed earlier, helping to prevent serious accidents. Remote, non-contact measurement allows assessment of fragile exterior materials without disturbing them, enabling safe inspection of severely deteriorated areas. Reducing the number of times scaffolding or aerial work platforms are used also contributes to lower inspection costs.

• Streamlined record-keeping and management: Acquired 3D point cloud data and geotagged photos have high value as records of deterioration. The overall condition of the exterior, which was difficult to convey in paper reports, can be shared in three dimensions through 3D models. Data stored and managed in the cloud makes it possible to digitally archive inspection histories by property and to track asset value and maintenance status over the long term. For example, you can compare and verify over time “what happened to the area repaired last time” or “whether a crack has not expanded over the past few years.” Strengthening traceability through digital archives enhances the persuasiveness of materials presented to building owners and management associations.

• Faster report generation: Digitized inspection data reduces the effort of preparing reports. Photos taken during inspection automatically include positioning information (coordinates and orientation), making it immediately clear which part of the building each crack photo represents. This reduces the burden of manually creating photo ledgers and deterioration distribution maps and increases report reliability. Listing deterioration marked on the 3D model enables immediate aggregation of the quantity and extent of areas requiring repair, eliminating the need to transcribe into drawings or spreadsheets to calculate quantities and allowing rapid, comprehensive report preparation. In practice, time spent making photo albums and drawings is significantly reduced, and stakeholders’ understanding of inspection reports has reportedly improved.

Useful across a wide range of sites from detached houses to public facilities

The 3D scan × AR inspection method can be applied regardless of building scale or structure. For detached houses, it is useful for diagnosing exterior deterioration and pre-repainting surveys, reliably identifying cracks and leaks. For large buildings such as apartment complexes and office buildings, digitalization can streamline the comprehensive exterior sounding surveys that were traditionally conducted over a long period with scaffolding prior to major repairs, enabling completion in a short time without affecting residents. Not erecting scaffolding during the survey also reduces noise and a sense of confinement for occupants and does not interfere with building use. For public facilities such as schools and government offices, digital inspection data helps with facility-specific maintenance plans. Using digital data enables objective situation assessment by facility managers and useful materials for administrative reporting. When managing multiple buildings, centralized management of each building’s inspection history provides objective criteria for prioritizing repairs. These advanced practices can also help construction and management companies showcase technical capability and differentiate themselves, increasing trust from clients and tenants.

Smart exterior inspections with the smartphone surveying system LRTK A noteworthy tool that makes on-site use of the latest 3D scan × AR technologies easy is the smartphone surveying system “LRTK.” LRTK is a small RTK-GNSS receiver that attaches to a smartphone or tablet, enabling centimeter-class high-precision GNSS positioning, photogrammetry-based 3D point cloud scanning, and stable AR display without drift—all with a single device. Conventional AR often required marker placement or manual alignment, but LRTK’s high-precision GNSS keeps AR objects consistently aligned with the real world. Precision measurement that formerly required expensive equipment and specialist surveyors can now be completed by a single field staff member with a smartphone in a short time.

Consider a case where LRTK is introduced for regular inspections of an apartment exterior. The inspector walks around the building perimeter scanning the exterior with a smartphone to acquire a 3D point cloud of the entire building. For taller buildings, drone images can be combined so that the topmost parts of the façade are captured without omission. For roof areas or upper stories not directly visible from the ground, integrating drone aerial photos with ground-acquired point clouds builds a complete building model. The point cloud model can be checked immediately on the smartphone screen, and additional scanning can be performed if any gaps are found. The completed 3D model can then be AR-displayed over the actual building on a tablet screen. While viewing the site through the tablet, the inspector can mark suspected deterioration on AR or record notes as text annotations. Tasks that previously involved guessing positions from paper drawings and marking them by hand can now be marked directly with the real wall and digital model aligned, making the process much more accurate and faster. In a trial estimate for a 30-year-old, five-story (about 50 units) apartment building, introducing LRTK reportedly reduced exterior inspection time by about 50% compared with conventional methods. Additionally, many fine cracks that were previously overlooked were detected in the data, confirming improved inspection accuracy.

Because LRTK embeds accurate position coordinates in all acquired data, recorded deterioration is automatically visualized on drawings and 3D models. For example, after an inspection, accessing the LRTK cloud system from an office PC displays the building elevation and 3D views with plotted crack and damage locations linked to photos and notes. This makes it easy to share inspection results with stakeholders online and collaboratively consider priorities and repair plans.

Typical workflow for digital exterior wall inspections

• On-site 3D scan – Measure the building perimeter with an LRTK-equipped smartphone to acquire the entire exterior as point cloud data.

• On-site verification with AR – Display the scanned 3D model as AR over the actual building. Overlay the model on the real object to check for deterioration without omission, and mark cracks or defects on site.

• Data sharing and analysis – Share recorded data internally via the cloud. If necessary, perform detailed analysis of point cloud data to objectively evaluate the extent and severity of deterioration.

• Report preparation – Use geotagged photos and marking information to create lists of deterioration and drawings. Organize inspection results clearly and submit them to stakeholders.

• Repair planning and construction – Decide repair methods and locations based on inspection data. Use AR to guide repair locations during construction, and re-scan after completion to verify repair effectiveness.

Use for re-inspection and repair work Digitized exterior inspection data is also very useful for subsequent maintenance. As mentioned, because a 3D model and deterioration records are retained, the locations recorded in the previous inspection will be AR-guided during the next scheduled visit. Inspectors can accurately identify “where a crack was previously” on a tablet and focus on the same spot to compare for new changes. Overlaying the previous point cloud model with newly acquired data allows quantitative evaluation of minute deformations or displacements over time. Detecting crack expansion or localized wall deflection digitally aids preventive maintenance decisions. This is effective for preventing recurrence and long-term tracking of deterioration, helping to avoid oversights. Sharing records with repair contractors allows them to determine required repair locations and quantities in advance, reducing the risk of discovering additional damage only after scaffolding is erected. On the repair day, workers can project repair location markings onto the wall using the tablet’s AR function to ensure no instructions are missed. After repairs, re-scanning with LRTK enables verification in digital data that repairs were properly executed. By repeating this survey→repair→verification cycle based on data, the PDCA cycle for building maintenance can be elevated in quality.

LRTK applications beyond exterior wall inspections While LRTK’s 3D scan × AR approach revolutionizes exterior inspections, its applications extend further. LRTK was originally developed as a simple surveying tool for all types of sites and performs in a variety of scenarios beyond construction, including civil engineering and facility management. For example, boundary surveying, earthworks progress (volume) management, and indoor 3D measurements for renovation planning can all be handled in-house rather than outsourcing to specialists, with expected cost savings. The highly accurate scanning and AR recording mechanisms that excel in exterior inspections can also be applied to infrastructure inspections of bridges and tunnels, deterioration checks of factory equipment, and monitoring roof or slope deformation. By connecting data from the field to the office, DX can be promoted to achieve both operational efficiency and safety. It is fair to say this technology brings a digital revolution to exterior wall inspection sites.

In recent years, technologies such as infrared cameras for detecting tile delamination and AI analysis of images to automatically detect cracks have also emerged in the field of exterior inspections. These offer the advantages of non-contact investigation (though infrared surveys can be affected by ambient temperature and solar radiation conditions, and AI accuracy depends on image quality and training data) and fast, wide-area image diagnosis. However, 3D point cloud scanning + AR is strong in that it can quantify overall wall shape changes and share information with stakeholders on site. By leveraging the strengths of each method in combination, safer and more reliable exterior inspections are possible. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the use of ICT and robotics to enhance infrastructure inspections, and the construction industry as a whole is accelerating DX initiatives. In the future, combining point cloud data with design BIM data and IoT sensor information could make it realistic to construct digital twins of buildings for continuous monitoring.

Why not adopt the latest technologies to protect the future value of your buildings while making inspection operations smarter? Once tried on site, you should be able to experience the benefits. Going forward, digital technologies such as 3D scanning and AR are expected to contribute not only to exterior inspections but to major productivity improvements across the construction industry and to alleviating labor shortages. Watch for further technological developments. The DX of exterior wall inspections will undoubtedly continue to expand—don’t get left behind.