Importance and Challenges of Exterior Wall Inspections The exterior walls of buildings are constantly exposed to rain, wind, and sunlight, and aging deterioration is unavoidable. If issues such as detached or fallen 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 aged mortar exterior walls fell and struck passersby. The cause was long periods without inspection, allowing cracks in the exterior and corrosion of internal metal members to progress. Regular exterior wall inspections are therefore indispensable to prevent such accidents.

However, traditional exterior wall inspections have mainly relied on qualified personnel performing visual inspections and hammer sounding (tapping with a hammer to check for delamination or voids). High-elevation inspections require erecting scaffolding or using aerial work platforms, which means that work time and costs are substantial, and there are inherent risks associated with high-elevation work. Moreover, visual-centric surveys are easily influenced by the inspector’s subjectivity, making it likely that small deteriorations will be overlooked or records omitted. Recently, the aging and shortage of skilled exterior-diagnosis technicians has become serious, and establishing a system for conducting inspections efficiently is a challenge. Marking damaged areas by hand on paper drawings made it difficult to record exact positions and dimensions, and it was also hard to quantitatively analyze conditions later or track changes over time.

Next-generation Exterior Wall Inspections Opened by 3D Scanning × AR To solve these challenges, digital inspections using 3D scanning technology and AR (augmented reality) have attracted attention in recent years. Laser scanners, drone aerial photography, and even smartphone LiDAR and photogrammetry can convert building exterior shapes into three-dimensional data without omission. If the entire wall surface is recorded as high-density point cloud data (a collection of countless measured points obtained by 3D scanning), it becomes possible to accurately capture crack lengths and even slight bulges in the exterior. Because the data can be stored in the cloud and analyzed in detail later, inspections can be more objective and reproducible compared with traditional visual methods. The use of 3D scanning is also positioned as foundational technology for the DX (digital transformation) of infrastructure maintenance promoted by the Ministry of Land, Infrastructure, Transport and Tourism.

Furthermore, combining this 3D data with AR dramatically transforms on-site exterior inspections. With 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 real object on site, deterioration areas can be intuitively identified without omission. It is also easy to mark crack locations on the AR display and record them on the spot, or to display drawing information in AR to navigate inspection targets. Because the high-precision model obtained by 3D scanning ensures that AR overlays do not drift, AR displays can match the real object precisely, enabling reliable inspection support.

Main Benefits of Introducing 3D Scanning × AR Below are five main benefits.

• Dramatic improvement in inspection accuracy: Digital scanning enables precise measurements at the millimeter- to centimeter-level (approximately 0.04–0.4 in), allowing detection of minute cracks and subtle deformations of exterior walls that the human eye might miss in the data. Deterioration, which was previously judged by feel, can now be quantitatively evaluated on 3D data—for example, by accurately measuring crack lengths or checking tile detachment in section. Because inspection results are less variable and judgments are based on the same objective data regardless of who conducts the survey, diagnostic reliability improves.

• Significant time savings: 3D scanning can measure wide exterior surfaces collectively in a short time, greatly reducing survey time compared with manual, detailed inspections. For example, even using a smartphone-based scan, data acquisition can be completed simply by walking once around the building. In practice, for a building about 30 m (98.4 ft) wide and 10 m (32.8 ft) high, an LRTK exterior point cloud scan can be completed in about 15 minutes. Because the need to erect scaffolding for detailed checks can be reduced, preparation and cleanup time is also reduced. For property management companies handling multiple buildings, the number of buildings that can be inspected in a day increases and operational efficiency improves dramatically. In extreme cases, surveys that used to require 3–4 people a full day have been reported to be completed by one person in about half a day with LRTK.

• Improved safety: Introducing scanning technology reduces the need for inspectors to work at height for extended periods. Combined with drones or high-magnification cameras, dangerous areas can be inspected remotely, and only locations that require close-up verification need concentrated inspection later, minimizing the risk of high-elevation work for personnel. With digital data, accurate repair plans can be devised, enabling prompt action on urgent repair areas and helping to prevent serious accidents. In addition, non-contact remote measurements allow assessment of fragile exterior materials without disturbing them, so even severely deteriorated areas can be inspected safely. Reducing the number of times scaffolding or aerial work platforms are used also contributes to lower survey costs.

• Efficient record keeping and management: Acquired 3D point cloud data and georeferenced photos themselves have high value as deterioration records. The overall condition of the exterior, which was difficult to convey with paper reports, can be shared three-dimensionally among stakeholders using 3D models. Data can be stored and managed in the cloud, enabling digital archiving of inspection histories for each property and long-term tracking of asset value and maintenance status. For example, it becomes possible to compare over time whether a previously repaired area has changed or whether a crack has expanded over several years. Strengthening traceability makes explanations to building owners or management associations more persuasive.

• More efficient report creation: Digital inspection data reduces the workload of report preparation. Photos taken during inspections automatically include positioning information (coordinates and orientation), making it immediately clear which part of the building each crack photo corresponds to. This reduces the burden of manually creating photo ledgers and deterioration distribution maps and improves report reliability. If deterioration locations marked on a 3D model are compiled into a list, the quantity and extent of areas requiring repair can be instantly totaled. This eliminates the need to transcribe into drawings or spreadsheets for quantity calculations, enabling rapid and comprehensive report creation. In practice, time spent on photo albums and drawing production has decreased significantly, and stakeholders’ understanding of inspection reports has reportedly improved.

Effective Across Sites from Single-Family Homes to Public Facilities

The inspection method using 3D scanning × AR can be applied regardless of building size or structure. For single-family homes, it is useful for diagnosing exterior deterioration and pre-repainting surveys, reliably identifying cracks and leaks. For large buildings such as condominiums and office buildings, the digitalization of large-scale wall tapping surveys—traditionally conducted by erecting scaffolding and spending long hours before major repairs—can streamline the process and complete inspections quickly without affecting residents. Not erecting scaffolding during surveys also reduces noise and a sense of confinement for occupants, minimizing disruption to building use. Public facilities such as schools and government buildings also benefit from digital inspection records in planning maintenance. Using digital data helps facility managers gain objective awareness of conditions and provides useful materials for explanations to authorities. When multiple buildings are managed, inspection histories can be centrally managed, providing objective data to prioritize repairs. Implementing these advanced approaches can also showcase technical capability and differentiation for contractors and management companies, enhancing trust from clients and occupants.

Smart Exterior Inspections Using the Smartphone Survey System LRTK A tool attracting attention for easily using the latest 3D scanning × AR technologies on site is the smartphone survey system “LRTK.” LRTK is a small RTK-GNSS receiver attached to a smartphone or tablet that enables centimeter-level (half-inch) high-precision GNSS positioning, photogrammetry-based 3D point cloud scanning, and stable AR displays that do not drift—all with a single device. Traditional AR required marker placement or manual alignment, but with LRTK, high-precision GNSS ensures AR objects are always displayed without offset from the real object. Precision measurements that once required expensive equipment or specialist surveyors can now be completed quickly by a single field staff member with a smartphone, which is a major advantage.

For example, consider introducing LRTK for routine inspections of a condominium exterior. The inspector first walks around the building perimeter and scans the exterior with a smartphone to acquire a 3D point cloud of the entire building. For tall buildings, drone images can be combined to ensure the entire façade up to the top of the building is captured. For rooftop or high-elevation areas not visible from the ground, integrating aerial photos taken by drone with ground-acquired point clouds constructs a complete building model. The point cloud model can be checked on the smartphone screen immediately after acquisition, and additional scans can be performed on the spot if necessary. The resulting 3D model can be AR-displayed over the actual exterior on a tablet. Inspectors can look around the site while holding the tablet, mark suspected deterioration on the AR model, and enter notes as annotations. Tasks that used to require guessing positions while holding paper drawings and marking symbols can now be done directly and much more accurately and quickly because the real wall and digital model are aligned. In one estimate for a 30-year-old, five-story (approximately 50-unit) condominium, introducing LRTK reduced exterior inspection time by about 50% compared with conventional methods. Additionally, many fine cracks that were previously missed were detected in the data, confirming improved inspection accuracy.

Because LRTK assigns accurate position coordinates to all acquired data, recorded deterioration locations are automatically visualized on drawings and 3D models. For example, after inspection, accessing LRTK’s cloud system from an office PC displays the building elevation and 3D view with plotted crack and defect locations, linked to photos and notes. This makes it easy to share inspection results online with stakeholders and smoothly discuss prioritization of deterioration areas and repair plans.

Typical Workflow for Digital Exterior Wall Inspections

• On-site 3D scanning – Use smartphone-equipped LRTK to survey the building perimeter and obtain the entire exterior as point cloud data.

• On-site confirmation with AR – AR-display the 3D model obtained by scanning onto the on-site building. Overlay model and reality to check for deterioration without omission, and mark cracks and defects on the spot.

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

• Report creation – Based on geotagged photos and marking information, create lists of deterioration and drawings. Organize inspection results clearly and submit to stakeholders.

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

Use for Re-inspections and Repair Work Digitized exterior inspection data is highly useful for subsequent maintenance. As mentioned, because 3D models and deterioration records remain, during the next periodic inspection the previously recorded deterioration locations are AR-guided on site. Inspectors can accurately locate “where a crack was before” by looking at a tablet and focus on the same area to compare for new changes. By overlaying the previous point cloud model with the latest data, small deformations or displacements over time can be quantitatively evaluated. Detecting crack expansion or local sagging digitally aids preventive maintenance decisions. This is effective for preventing recurrence and long-term deterioration tracking and helps prevent oversights. Sharing record data with repair contractors allows them to know required repair locations and quantities in advance, reducing the risk of finding additional damage only after scaffolding is erected. On the repair day, field staff can project AR markings of repair locations onto the wall with a tablet to ensure no instructions are missed and the correct parts are repaired. After repairs, re-scanning with LRTK makes it possible to verify digitally whether repairs were carried out appropriately. Running this survey→repair→verification cycle based on data raises the quality of the building maintenance PDCA.

LRTK Applications Beyond Exterior Inspections While 3D scanning × AR with LRTK revolutionizes exterior inspections, its applications are even broader. LRTK was originally developed as a “simple surveying tool” for all kinds of sites and is useful not only in construction but also in civil engineering and facilities management. For example, boundary surveys, as-built control for earthworks, and indoor 3D measurements for renovation planning—tasks that previously required specialist contractors—can be performed in-house easily. This can also reduce related costs. The high-precision scanning and AR recording mechanisms that excel in exterior inspections can also be applied to bridge and tunnel infrastructure inspections, plant equipment deterioration checks, roof and slope deformation monitoring, and more. Connecting data from the field to the office promotes DX, achieving both operational efficiency and safety. It is truly a technology that 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 for automatic crack detection have also emerged in the field of exterior inspections. These non-contact methods (though infrared results can be affected by ambient temperature and sunlight conditions, and AI accuracy depends on image quality and training data) offer the advantage of examining internal defects and quickly diagnosing large areas by image. However, 3D point cloud scanning + AR is strong in quantifying shape changes of the entire wall surface and sharing information on the spot with stakeholders. Combining the strengths of each method can enable safer and more reliable exterior inspections. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the use of ICT and robotics to enhance infrastructure inspection, and DX in the construction industry is accelerating. In the future, integrating point cloud data with design BIM data and IoT sensor information to construct a digital twin of buildings for continuous monitoring is becoming increasingly feasible.

Why not adopt the latest technologies to protect future building value while making inspection work smarter? Once tried on site, you should be able to appreciate the benefits. Going forward, digital technologies such as 3D scanning and AR are expected not only to transform exterior inspections but also to significantly improve productivity across the construction industry and help address labor shortages. Watch for further technological developments. The DX of exterior wall inspections will only continue to expand. Be sure not to be left behind by this trend.