Part K stairs: the Irish rules explained
Part K of the Irish building regulations covers stairways, ladders, ramps and guards. If you are having a stair made, these are the numbers that shape what is possible in your opening.
Rise and going
The rise is the height of each step and the going is the depth of the tread. For a private stair in a dwelling, Irish guidance limits the rise and sets a minimum going, and the two are linked so that a steeper rise requires a deeper going within a stated relationship.
Every rise in a flight must be equal. This is the single most common reason a stair fails inspection: a builder pours a floor screed after the stair is fitted and the bottom riser ends up shorter than the rest. Tell us the finished floor levels, not the structural ones.
Headroom and width
Headroom is measured vertically from the pitch line of the stair, and the standard requirement for a dwelling is 2 metres. Attic conversions are where this bites, because the stair often rises into a sloping roof and the opening has to be positioned to keep the headroom.
Width is less prescriptive for private stairs than people expect, but usability and furniture movement matter. Public and commercial stairs have their own widths driven by occupancy and escape.
Guarding and gaps
Guarding is required to the open sides of a flight and landing. In dwellings the guard height on a flight is generally 900mm measured from the pitch line and 1100mm to landings and balconies, with commercial buildings taking higher figures in places.
The 100mm sphere rule applies: no opening in the guarding should allow a 100mm sphere to pass. That governs the spacing of vertical bars and rules out horizontal bars that could be climbed in dwellings where children are present.
How this affects a steel stair
All of this is settled at drawing stage, before any steel is cut. We set out the flight against the measured floor to floor height, check the headroom against the opening and design the balustrade to the guarding and gap requirements.
This article is a plain language summary rather than a legal reference. Your architect, engineer or assigned certifier confirms what applies to your specific building, and we build to that.
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Common questions
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