How should wall and floor damage categories be read?
Owners and building professionals
Wall and concrete-floor damage categories use different measurements, and the conditions and notes must stay attached. A commonly quoted six-category wall chart is a different framework from the five-category wall and floor tables shown later. Read the descriptions and limits together rather than comparing crack widths alone.
If cracking or movement is affecting your property, explore our investigation of cracking and building movement. An article cannot determine the cause or appropriate solution for an individual property.
Crack-width categories can help professionals describe damage consistently. They cannot determine the cause, structural safety or repair design from a width alone. The six-category damage table below has qualifications on its use. Read the descriptions and limitations together.
The table describes more than millimetres
The first wall table groups visible damage into categories 0 to 5, accompanied by descriptions of typical damage and related repair characteristics. The approximate width ranges include up to 0.1 mm, 0.1-1 mm, 1-5 mm, 5-15 mm, 15-25 mm and more than 25 mm. These are descriptive ranges, not instructions for homeowner classification.
The shared endpoints and the word approximate matter. The table also discusses multiple cracks and other symptoms. Do not turn the ranges into a new set of exact, non-overlapping safety boundaries or assume a crack at an endpoint must fall into one particular category.
Category is not cause or safety
Factors including increasing width can affect classification. Construction, distortion, function and the complete pattern require assessment. A small crack may accompany a condition that needs attention, while width alone does not explain a larger one.
The copied table is included for basic background and professional discussion. Its repair descriptions are part of the source classification, not recommendations to perform those repairs. An engineer must decide what response fits an actual building.
Do not transfer categories to other elements
Concrete-floor damage uses a separate table with its own application limits. Wall crack categories should not be applied automatically to floor slope, level differences or wall lean.
The first six-category framework is not an Australian compliance table. It must not be substituted for the separate five-category wall and concrete-floor classifications below.
Use the reference to improve the record
Record material, location, repeatable width points, length, related symptoms and change over time. Provide that evidence to the professional rather than self-assigning a category to decide whether to wait or repair.
For a hypothetical owner comparing two cracks of similar width, one is unchanged in a finish while the other accompanies worsening door distortion. The same width does not make the evidence patterns equivalent. Sudden distress or instability requires prompt advice regardless of a table range.
Useful Next Steps
- Read both table excerpts with their original descriptions.
- Keep approximate ranges separate from safety and compliance decisions.
- Record progression and related symptoms as well as width.
- Ask the professional how any category was assessed and what it means in context.
A different five-category wall and floor framework
The six-category wall table reproduced above has its own categories and qualifications. It must not be relabelled as the five-category classification. The separate normative tables for walls and concrete floors shown below are both numbered from Category 0 to Category 4.
The five-category wall table combines approximate width limits with typical damage and three notes. Grouped cracks and serviceability matter. The first note allows increased width limits in the stated easily repaired plasterboard or similar clad-framed partition context; it does not justify increasing the limit for every wall finish. The category descriptions and repair wording are classification background, not owner-selected repairs.
The table's less-than entries are not rewritten here as neat non-overlapping intervals. Do not add a Category 5, infer a missing endpoint rule or substitute another source's boundary. A professional needs to explain the classification applied to the actual material and damage.
The concrete-floor table measures something else
The concrete-floor table includes approximate crack limits and change in offset from a 3 m straightedge centred over a defect. Its first note describes equal-height end spacers and a straightedge that is not necessarily horizontal. That is a local measurement relationship, not the maximum spread across a room or whole-house level survey.
The remaining notes address visible or undesirable deviation context and past damage history. Assessment also needs to allow for level deviations from construction and consider whether damage is stable or increasing. A single modern level plan cannot reconstruct the original floor or supply a movement rate.
Keep design values out of a condition comparison
Characteristic ground movement and design differential deflection answer other questions again. Neither can be swapped for the concrete-floor table's local offset or treated as a universal existing-floor acceptance criterion.
Provide the assessor with dated crack records, point locations, floor survey method and datum, related functional symptoms and known work history. Ask which table, edition, quantity and qualifications support any reported category. No category is a stand-alone safety verdict. Falling material, wall instability, sudden floor change or other urgent distress calls for immediate appropriate advice regardless of width.