Defect type
High · 2–4/5
Stair Riser or Going Outside NCC Dimensional Limits
I measured riser heights and going depths across the flight and recorded dimensions outside the NCC 3.9.1 reference range, or I found more than 5mm variance between risers or goings in the same flight. In my experience non-standard dimensions cause trips and miscued steps, especially for elderly occupants and children. I see this frequently on owner-built renovations and in pre-1970 housing where the flight was cut to fit the available floor-to-floor height rather than set out to a published range.
Causes
- Owner-builder cutting stair stringers to fit restricted floor-to-floor rise
- Original construction predating current dimensional references
- Landing added or removed altering the riser count and distribution
- New floor covering (tile, overlay) added without adjusting the top or bottom riser
- Deck or external stair built to a handyman rule-of-thumb rather than a referenced range
Symptoms to look for
- I measured a riser at less than 115mm or greater than 190mm
- I measured a going at less than 240mm or greater than 355mm
- First or last riser varies from intermediate risers by more than 5mm on my tape
- Occupants reporting trips, missed steps, or an awkward rhythm when descending
- Visibly inconsistent riser heights along a single flight
Remedies
- Rebuild the flight with consistent risers and goings; confirm against NCC 3.9.1
- Shim or pack the top or bottom tread to equalise riser heights
- Remove recent floor overlay contributing to the mismatched top riser
- Engage a licensed carpenter to recut stringers to a referenced stair geometry
- Fit high-visibility nosings as an interim measure while remediation is scheduled
Critical
Get an inspector through this property.
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