Irish Stair & Barrier Rules: Rise, Going, Handrails, Guarding

The requirement

For a private stair, each rise can be at most 220 mm, each going at least 220 mm (TGD K 2014, Table 1). The optimum is a 175 mm rise on a 250 mm going. The maximum pitch is 42°, with 35° the optimum (par. 1.1.4).

Two words to know. The rise is how tall each step is. The going is how deep it is, the flat part you stand on. These numbers come from TGD Part K, the Technical Guidance Document for Stairways, Ladders, Ramps and Guards. Its 2014 edition is the deemed-to-satisfy route under the Irish Building Regulations. Keep every step in a flight the same, so the stair climbs evenly.

A stair also has to pass the 2R+G check. That means twice the rise plus the going. Table 1, Note 4 sets it between 550 mm and 700 mm, with 600 mm the optimum. It is a quick way to spot a stair that is too steep or too shallow before you cut a stringer.

Two more numbers finish it off:

Headroom. At least 2000 mm clear above the stair (par. 1.1.9, Diagram 3). In a loft conversion that can drop to 1900 mm at the centre line of the stair. A minor side projection can come down to 1800 mm.
Width. A private stair needs a clear width of at least 800 mm (par. 1.1.10). A flight also cannot run more than 16 risers without a landing (par. 1.1.11).

TGD K 2014 · Table 1

Guards & barriers

The handrail sits 900–1000 mm above the pitch line on a flight, and 900–1100 mm above a landing (par. 1.1.17). Fit it to one side if the stair is 1000 mm wide or less. Fit it to both sides if the stair is wider.

Guarding protects any edge a person could fall from. In a single-family dwelling, TGD K’s Diagram 6 (par. 1.1.20) sets the guard heights.

Where	Guard height
Stair, ramp or landing	900 mm
Floor, balcony or roof edge	1100 mm

The gaps in the guarding matter too. A small child must not fit through.

A 100 mm sphere must not pass through any opening in the guarding.
The guarding must not be readily climbable.
A cut-string stair has an open triangle under each tread, between the tread, the riser and the string. That gap is not allowed in a dwelling (par. 1.1.19).

Work it out on site

Say your floor-to-floor height is 2800 mm and you are setting out a private stair.

Pick how many risers. 2800 ÷ 220 = 12.7, and 220 mm is the tallest a rise can be. You cannot have part of a step, so round up to 13 risers. 2800 ÷ 13 = 215 mm per rise. That is under the 220 mm limit. It also sits well inside the 16-riser limit for a single flight.
Set the going. Try 250 mm. Assuming the upper floor is the final tread, thirteen risers give 12 goings: 12 × 250 = 3000 mm of horizontal run. Check that fits the space.
Check both formula and pitch. Use the unrounded rise, 2800 ÷ 13 ≈ 215.38 mm. Then 2R+G ≈ 680.77 mm, inside the 550–700 mm band. The pitch is arctan(215.38 ÷ 250) ≈ 40.75°, below 42°. A 220 mm going would give about 44.39°, so it would fail the pitch limit even though its 2R+G value is within range. Check the other requirements too.

The web tool calculates equal rise and 2R+G for your chosen riser count. Compare those results and the pitch against the applicable requirements.

Do it in 5 seconds

Irish Building Regulations hub — how the one national rule book and its TGDs work.
UK stair and barrier requirements — the Approved Document K numbers, for anyone comparing across the Irish Sea.

Sources

TGD Part K (2014) — Stairways, Ladders, Ramps and Guards, Table 1 (rise, going, pitch and 2R+G), par. 1.1.9 / Diagram 3 (headroom), par. 1.1.10–1.1.11 (width and risers per flight), par. 1.1.17 (handrail height) and par. 1.1.19–1.1.20 / Diagram 6 (guarding). Read it at gov.ie.

Read this first. The figures above are from the 2014 edition of TGD Part K, in force since 1 January 2015 — this is the deemed-to-satisfy route, not the only legal one. A superseded 1997/2005 edition of TGD K still circulates online and gives different numbers: a handrail of 840–900 mm and a private-stair guard of 840 mm. TGDs also carry transitional arrangements, so the edition in force can vary by the commencement or permission date of your job. Always confirm you’re reading the current edition on gov.ie before you build to it.

Frequently asked questions

What is the maximum rise and minimum going for a stair in Ireland?

TGD Part K (2014), Table 1 sets it for a private stair. Each rise can be no more than 220 mm, with 175 mm the optimum. Each going must be at least 220 mm, with 250 mm the optimum. Keep every rise and going in the flight the same.

What is 2R+G and what does it need to add up to?

2R+G means twice the rise plus the going. It is a quick check that a stair is a comfortable steepness. TGD K Table 1, Note 4 sets it between 550 mm and 700 mm, with 600 mm the optimum. Outside that band, the stair feels too steep or too shallow.

How much headroom does an Irish stair need?

TGD K par. 1.1.9 (Diagram 3) sets a minimum of 2000 mm clear headroom over the stair. In a loft conversion that can come down to 1900 mm at the centre line of the stair, and to 1800 mm at a minor side projection.

How high should the handrail and guarding be?

The handrail sits 900–1000 mm above the pitch line on a flight, and 900–1100 mm above a landing (TGD K par. 1.1.17). Guarding in a single-family dwelling is 900 mm at a stair, ramp or landing, and 1100 mm at a floor, balcony or roof edge (par. 1.1.20, Diagram 6).

Are these the current TGD K numbers?

Yes. These figures come from the 2014 edition of TGD Part K, in force since 1 January 2015. An older 1997/2005 edition still floats around online. It gives a handrail of 840–900 mm and a private-stair guard of 840 mm. Check you have the current edition for your job before you build.