Office building and facade inspection: checking glass and cladding before anything falls

Facade materials differ greatly by era. Older buildings tend to have tile, mortar and stone cladding; newer high-rises mostly use curtain walls — glass and metal panels hung on a frame. They deteriorate differently, but the common thread is that fixings and joint seals weaken first.

Facade inspection on office buildings centres on gondolas (cradles suspended from the roof) and rope access. Many high-rises have window-cleaning gondolas, but using them for inspection means scheduling, and they stop in strong wind. Buildings without one must hire scaffolding or aerial lifts.

In the city centre, protecting people below becomes the biggest effort: fencing off pavements, posting guards, sometimes occupying the road. With tenants’ business and pedestrian flow in mind, work tends to be pushed into nights and weekends.

The drone brings a camera in front of a tall wall and captures the whole face under consistent conditions. A face that would take a gondola days can be covered quickly. Infrared screens tiles for delamination; high-resolution imagery shows cracks, sealant failure and rusted fixings. A 3D model ties every finding back to the drawings.

To know the defects by name before you shoot, read the types of facade defects and how to tell them apart (Airffic World).

A business district is crowded, gusty and GNSS-unreliable for drones. Between tall buildings, satellite signals bounce and positions drift (multipath). Wind accelerates and changes direction around corners and through street canyons. And there is always someone below.

• Urban areas & people below: control access to pavements and entrances and plan routes that avoid flying over people. Tenants and passers-by need to be informed. Urban areas & people below
• Height: at roof level the aircraft is hard to see from the street. Post observers on the roof and on the ground. Height
• Wind & turbulence: building-induced wind is nothing like ground-level wind. Measure on the roof and keep an escape path away from the wall. Wind & turbulence
• GNSS-denied: GNSS degrades the closer you get to the wall. Choose aircraft with vision positioning and obstacle sensing, and decide in advance to back away from the wall if position wanders. GNSS-denied

A full survey of a high-rise yields thousands of images. Identifying which floor, which face, which panel, picking out defects and comparing with last time — machines help a great deal with all of that. Deciding whether something could fall is still a human call.

In Japan, Article 12 of the Building Standards Act sets up the periodic reporting system: owners or managers of designated buildings of certain uses and sizes have a qualified person, such as an architect, inspect them and report to the designated administrative agency, at intervals the agency sets, generally between six months and three years. Separately from the building itself, building services and fire-protection equipment have their own periodic inspection and reporting rules.

For facades, a 2008 notice revision requires that tile, stone and mortar facades be checked by full-surface sounding or equivalent on the parts that could injure pedestrians if they fell, once more than ten years have passed since completion, facade renovation or the last full-surface sounding. A January 2022 revision made explicit that infrared surveys by drone (unmanned aircraft) with accuracy equal to or better than test-hammer sounding may be used, and MLIT has issued guidelines on infrared surveys including by drone. Note that the full-surface sounding concept does not map directly onto curtain-wall glass or metal panels; what to check must be decided material by material.

Other cities also mandate periodic facade inspection: New York City requires buildings over six storeys to have facades inspected every five years (FISP); Singapore has since 2022 required facade inspection every seven years for buildings above a set height that are more than 20 years old (visual inspection by accredited drone service providers is allowed); Hong Kong requires periodic inspection of private buildings aged 30 years or more. How far drones can be used also depends on each city’s flight rules. In Japan, facade flights are often specified flights — over densely inhabited districts or within 30 m of people or property — needing permission or approval depending on conditions. Compare countries in world regulations.

How a drone facade survey fits the periodic reports building owners already file is covered in how to survey a facade by drone without scaffolding (Airffic World).

• How tight the fixings are: whether bolts holding panels or glass have loosened often cannot be seen from outside. Check by hand or from inside.
• Flaws inside glass: internal inclusions that can cause spontaneous breakage of toughened glass are invisible in photographs.
• Infrared in poor conditions: overcast skies, wet walls, unlit faces, glass and metal surfaces can all hide delamination.
• Emergency measures: if something is about to fall, removing or securing it takes human hands.
• Judgement and accountability: the qualified inspector is responsible for the results in the periodic report.

What follows is the editors’ outlook. A small drone hangar sits on the roof. In the quiet early morning, the drone traces the facade on a fixed route, photographing each panel from the same pose as last time. The building management system lists only the panel IDs that have changed.

The gondola drops straight to what was found. Pavements are no longer closed for days for inspection. Facade inspection shifts from a big job every few years to an everyday part of keeping the street safe.