Ironbridge Inspect · structural defect grades
Grade the crack by what the member holds up.
Ironbridge Inspect grades defects in reinforced-concrete buildings in Nigeria by the structural member they sit on and what that member holds up, and says how soon an engineer has to see them.
IRONBRIDGE INFRASTRUCTURE TECHNOLOGIES LIMITED (Ironbridge) — Ibadan, Oyo State, Nigeria.
Try the member checkWhy this, why here
A crack in a ground-floor column is not a crack in a wall.
Nigeria recorded 47 building collapses across 14 states in 2024, and 52 the year before; Lagos led 2024 with 13 [S1]. Most of those buildings showed something first — a crack, a spall, a sag — to people who had no way to tell which of them could wait.
The same 2 mm crack means different things on different members. In a block wall it may be movement worth recording. Diagonal, in the ground-floor column that holds up two floors and a water tank, it is the reason to clear the room. Ironbridge Inspect reads the defect together with the member and what sits on it.
Live · runs in this page
The member check
Pick a member on the frame, say what you see, how wide it is and where the building stands. The grade comes with its reasons: what the member holds up, what the pattern usually means, and which width limit it was read against. Nothing leaves this page.
Grade · worked example
Clear the space it holds up, prop it, and get a COREN-registered engineer today.
- Member
- Ground-floor column C2 (middle)
- Holds up
- both first-floor beams, column C5 above it, both roof beams and the middle of both slabs
- Pattern
- Diagonal crack — In a column a diagonal crack usually means shear — the way a column fails with the least warning.
Width 0.3 – 1 mm: over the ACI 224R tolerance for humid or moist air: 0.30 mm.
- Starts at 3 for this pattern on a column.
- +1: it carries two floors.
A grade is triage, not a structural assessment. Grades 3 and 4 always end with a COREN-registered engineer.
The rules the check uses
| Member | Pattern | Starts at | Width read | What it usually means |
|---|---|---|---|---|
| column | Diagonal crack | 3 | yes | In a column a diagonal crack usually means shear — the way a column fails with the least warning. |
| column | Horizontal crack | 2 | yes | Bending at a joint, or the column taking more load than it was drawn for. |
| column | Vertical crack along the bars | 2 | yes | Usually reinforcement rusting, swelling and splitting the cover; left alone it becomes spalling. |
| column | Crushing or bulging near the top or bottom | 4 | — | The concrete itself is failing under the load it carries. |
| column | Spalling with bars showing | 3 | — | The cover is gone and the bars are open to air and water; whether they have lost section decides the repair. |
| column | Honeycombing: voids and loose stones | 3 | — | Poor compaction when it was cast — the column holds less concrete than the drawing assumes. |
| beam | Vertical crack at mid-span, underneath | 1 | yes | Bending. Fine cracks here are normal in reinforced concrete; wide ones are not. |
| beam | Diagonal crack near a support | 3 | yes | Shear close to the support — the same warning sign as a diagonal crack in a column. |
| beam | Crack along the bottom bars | 2 | yes | Reinforcement corroding inside the beam and pushing the cover off. |
| beam | Visible sag | 3 | — | The beam is deflecting more than it should; what it carries may be heavier than it was designed for. |
| beam | Spalling with bars showing | 2 | — | The cover has come away and the bars are exposed. |
| slab | Fine map cracking on the surface | 1 | yes | Shrinkage while the concrete cured; usually confined to the surface. |
| slab | Crack on top along a support line | 2 | yes | The slab bending over the beam or wall that supports it. |
| slab | Sag at mid-span with cracks underneath | 3 | — | The slab is deflecting between its supports. |
| slab | Rust stains or bars showing underneath | 2 | — | Reinforcement corroding close to the soffit. |
| wall | Hairline cracks in the plaster | 1 | yes | Plaster shrinkage; on its own it says little about the frame. |
| wall | Diagonal crack from a door or window corner | 2 | yes | Movement in the frame around it, or in the ground below. |
| wall | Gap opening between the wall and a column | 2 | yes | The frame and the infill moving apart. |
| wall | Bulging or leaning | 3 | — | The wall is out of plane; keep people clear of it until it is checked. |
Adjustments: reinforced-concrete crack widths are read against the ACI 224R tolerance for the exposure you pick [S2] — inside it, a grade-2 pattern drops to 1; over 1 mm adds 1; over 5 mm adds 2. Block-wall cracks are read against the BRE Digest 251 categories [S3] — category 3 or above adds 1. A ground-floor column adds 1 because it carries two floors. A crack that has widened since it was last recorded adds 1. Grades run from 1 to 4.
How it works
From a photograph to a grade.
Live today: the member check, in the browser, on fixed engineering rules. In development: photo reading that places each defect on its member. Next: a building record that tracks every crack between visits.
Member check
The rules above, in the browser, on any phone. Member, pattern, width and exposure in; a grade from 1 to 4, the action and the time limit out — with every step of the reasoning shown.
Photo reading
From a set of site photographs, place each crack or spall on the member it belongs to, measure it against a scale card in the frame, and hand that to the same grade rules.
Building record
One member map per building. Each visit is compared with the last, so a crack that is widening is caught by its change, not only by its size.
NVIDIA
Today we run our spatial reasoning models on an NVIDIA RTX PRO 6000, with CUDA and PyTorch: from a set of site photographs they place each crack or spall on the column, beam, slab or wall it belongs to, and reason about what that member holds up.
| Component | Status | What it does for us |
|---|---|---|
| NVIDIA RTX PRO 6000 | In use | Runs the spatial reasoning models that tie each defect in a photograph to its member and to what that member holds up. |
| CUDA · PyTorch | In use | The training and inference stack those models are built on. |
| NVIDIA TensorRT | Next | Serve the photo model so the photographs from one site visit come back graded in seconds. |
| NVIDIA Omniverse · OpenUSD | Next | Keep each building's member map as a 3D twin that every re-inspection updates. |
Built for
The people who have to decide what can wait.
Checking their own sites between pours, before a defect is plastered over.
Of occupied buildings, who need to know which crack to spend on first.
Who want a defect record, member by member, before they cover a building.
Sorting complaints so the worst buildings are seen first.
Width limits for reinforced concrete [S2]
| Dry air or protective membrane | 0.41 mm |
| Humidity, moist air, soil | 0.30 mm |
| Seawater spray, wetting and drying | 0.15 mm |
| Water-retaining structures | 0.10 mm |
Damage categories for block walls [S3]
| 0 · negligible | under 0.1 mm |
| 1 · very slight | up to 1 mm |
| 2 · slight | up to 5 mm |
| 3 · moderate | 5 – 15 mm |
| 4 · severe | 15 – 25 mm |
| 5 · very severe | over 25 mm |
A grade is triage, not a structural assessment. Grades 3 and 4 always end with a COREN-registered engineer. [S4]
Company
Ironbridge
IRONBRIDGE INFRASTRUCTURE TECHNOLOGIES LIMITED (Ironbridge) — Ibadan, Oyo State, Nigeria.
Founded and built by Abd'hakeem Musa Olamilekan, Founder — sole founder, and the person who writes the code.
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