RC Stair Design to Eurocode 2: A UK Guide

Designing a reinforced concrete stair in the UK means setting out a flight that satisfies Approved Document K, loading it to BS EN 1991-1-1 and its UK National Annex, then checking bending, deflection and cracking to BS EN 1992-1-1 (Eurocode 2). The load path in a standard flight is simple. The mistakes tend to come from how you idealise the supports and how you pick the waist thickness, not from the arithmetic. This guide takes you through the geometry, the loads, a worked example and the detailing, in the order a checker will read them.

TL;DR

• Set the geometry first. For a private stair in England, Approved Document K allows a rise of 150 to 220 mm, a going of 220 to 300 mm and a pitch of no more than 42 degrees.
• Dead load acts along the slope, while imposed and finishes loads are taken on plan. Mixing the two up is the commonest arithmetic slip.
• Domestic stairs are normally designed for 2.0 kN/m² imposed load. Public or institutional stairs can need much more, so check the occupancy category in the National Annex.
• Deflection often governs the waist thickness, and shear links are frequently unnecessary in a longitudinally spanning flight.
• How you idealise the supports (simple span, continuous, or built into a landing) changes moments and deflection more than any refinement in the analysis.

Table of Contents

• Start with the geometry that Building Regulations allow
• Choosing the structural form
• Loads on a concrete stair
• Worked example: a simple domestic flight
• Stiffness often governs, not strength
• Idealising the supports honestly
• Eurocode 2 and the transition to the second generation
• Detailing a flight so it can be built
• Our view on RC stairs
• When to hand stair design to an embedded engineer
• Checks before you issue
• FAQ
• Sources

Start with the geometry that Building Regulations allow

Structure follows geometry, so fix the going, rise and pitch before you size a slab. For private dwellings in England, Approved Document K sets a rise of 150 to 220 mm, a going of 220 to 300 mm and a maximum pitch of 42 degrees. The same guidance gives the sense check that twice the rise plus the going should fall between 550 and 700 mm. General access stairs in non-dwellings are tighter: a rise of 150 to 170 mm and a going of 250 to 400 mm.

Two practical points from a summary of Part K for England are worth keeping in mind. The figures apply to England under the 2013 edition, and Wales and Scotland differ, so say which jurisdiction your calculation package assumes. A landing is also required at the top and bottom of every flight.

From the architect’s drawings you need, for each flight:

• going and rise, giving the pitch and the slope factor
• horizontal span between supports, measured on plan
• landing lengths and widths, and what supports each one
• finishes, balustrade fixings and any nosing detail
• fire rating and exposure class, which drive cover

If the architect’s step dimensions change late, your load and slope factor change with them. Build the calculation so these inputs are in one place.

Choosing the structural form

RC stairs are built in several forms: straight flights, inclined slabs with half landings, string beams, cranked slabs and cantilevers. Most UK commercial and residential work falls into three.

For a standard dog-legged flight, the structural logic is straightforward, and practitioner guidance makes the same point: the effort belongs in boundary conditions and thickness estimation rather than elaborate modelling. A finite element model of a simple flight rarely tells you more than a clean one-metre-strip hand calculation, and it is harder to check.

Loads on a concrete stair

Permanent actions

Three components make up the dead load:

1. Self-weight of the waist slab, calculated along the slope. Convert it to a load per square metre on plan by multiplying by the slope factor, which is the slope length divided by the going.
2. Self-weight of the steps, taken as a triangle of concrete. On plan, this is half the rise multiplied by the concrete density.
3. Finishes and balustrade, usually a nominal allowance per square metre on plan plus a line load at the edge where the balustrade is fixed.

The principle, set out in the BCA’s guidance on precast staircases, is that dead load is calculated along the sloping length while live and finishes loads are based on plan area. It is a Singapore document, but the mechanics are universal.

Imposed actions

Imposed loads come from BS EN 1991-1-1 and its UK National Annex. Residential stairs typically take a distributed load of 2.0 kN/m² and a concentrated load of 2.0 kN. The National Annex’s Table NA.3 maps load categories to occupancies: domestic areas under Category A generally use 2.0 kN/m², while institutional or public areas under Category C may require substantially higher values, up to 5.0 kN/m². Confirm the category with the project’s design brief rather than assuming the domestic value, particularly for stairs serving assembly spaces, schools or offices with escape duties.

Worked example: a simple domestic flight

This is an illustrative calculation of our own to show the sequence, not a design for any real project. Assume a flight supported at top and bottom with no restraint, to keep it conservative.

Inputs

• Going 250 mm, rise 175 mm (pitch about 35 degrees, inside the Part K limits)
• Horizontal span 3.6 m, waist 150 mm
• C30/37 concrete, B500 reinforcement, 25 mm cover, 12 mm bars
• Finishes allowance 1.0 kN/m² on plan, imposed load 2.0 kN/m²

Permanent load on plan

• Slope length for one step: √(250² + 175²) = 305 mm, so the slope factor is 305 / 250 = 1.22
• Waist: 0.15 × 25 × 1.22 = 4.58 kN/m²
• Steps: 0.5 × 0.175 × 25 = 2.19 kN/m²
• Finishes: 1.0 kN/m²
• Total gk = 7.77 kN/m²

Ultimate load

n = 1.35 × 7.77 + 1.5 × 2.0 = 13.5 kN/m², or 13.5 kN/m per metre width.

Bending

• M = 13.5 × 3.6² / 8 = 21.9 kNm/m
• d = 150 − 25 − 6 = 119 mm
• K = M / (b d² fck) = 21.9×10⁶ / (1000 × 119² × 30) = 0.051, which is well below 0.167, so no compression steel is needed
• Lever arm z ≈ 0.95d = 113 mm
• As = M / (0.87 fyk z) = 21.9×10⁶ / (435 × 113) ≈ 445 mm²/m
• Provide H12 at 250 mm centres (452 mm²/m)

Shear

Maximum shear at the support is about 13.5 × 3.6 / 2 = 24 kN/m. For a flight like this, the induced shear stress is typically low. Practitioners often show it is below half the concrete shear resistance, which means no links are needed. You still have to demonstrate it on the page.

Deflection

The span to effective depth ratio here is 3600 / 119, about 30. Compare it with the Eurocode 2 limit for the reinforcement percentage and stress you have provided, and modify it as the code requires. Eurocode 2 permits an increase of 15% in the permitted ratio where the stair flight occupies at least 60% of the span, according to the same practitioner guidance. Check the clause in the code before taking the benefit, and do not use it where the flight is shorter than that.

If the check fails, you increase the waist by 10 or 20 mm. You do not add more steel as a first resort, since extra bars barely change the span to depth outcome.

Stiffness often governs, not strength

A stair is an evacuation route, and people notice a bouncy one. Research on stair design stresses that stiffness matters as much as strength, and that serviceability checks on deflection are often more critical than ultimate limit state checks. In practice that means:

• Start with a waist of span/25 to span/30 as a trial and let the deflection check confirm or reject it.
• Treat long, slender, lightly reinforced flights with suspicion, especially in offices or schools.
• Check crack widths where the stair is externally exposed or has brittle finishes such as stone or tile.

Slab thickness also drives cover and fire resistance, so a waist that works for deflection should still be tested against the project’s fire rating.

Idealising the supports honestly

This is where most real errors sit. Assuming a simple span when the geometry restrains the flight can give significant errors in moments and deflection, as the FPP guidance notes. Questions to ask before you write down the span:

• Is the flight cast monolithically with the landing, or does it sit on a nib or a bearing?
• Does the wall or beam beneath provide any torsional restraint to the end of the slab?
• Is the landing itself supported on two sides, three sides or a core wall?
• Does one flight bear onto the landing of another? If so, the landing is a supporting member for the next flight and must be modelled as such, not as a continuation of the stair.

When you cannot be sure, design for the worst case in each check. Use a simple span for sagging moment and deflection. Provide top steel at the support for the hogging that will develop if the junction turns out to be restrained, and for the cracking that would otherwise appear there.

Eurocode 2 and the transition to the second generation

Structural design of UK RC stairs follows BS EN 1992-1-1. The 2004 version with amendments remains the working standard. The second-generation code has been published as BS EN 1992-1-1:2023, and full replacement is scheduled for 30 March 2028. For a project that will be designed now and built over the next year or two, state on the calculation cover sheet which edition you have used, and flag the issue if the contract runs into the transition period.

Detailing a flight so it can be built

The calculation is only half the deliverable. A contractor builds from the drawing, so the detail needs to capture:

• Main bars along the flight, with the bar diameter and spacing from the calculation, and distribution steel in the transverse direction.
• Top steel at supports and landings, anchored properly even where the design assumed a simple span.
• Inside corner reinforcement where the flight meets the landing. Where the bars change direction under tension, they tend to straighten and push the concrete off. Use separate lapped bars rather than continuous bent bars.
• Laps and anchorage to match the code, with the lap length shown.
• Cover and bar bending references that tie to the schedule.
• Builder’s work information, such as pockets, nibs, balustrade fixings and construction joints.

Our Eurocode 2 checklist for UK reinforced concrete drawings covers the drawing checks that prevent rework on site, and the same discipline applies to a stair sheet as to a slab layout.

Calculation and model should also stay in step. Integrating BIM with the stair calculation helps firms move from calculation to review-ready documentation faster, and it ensures that details like how landings support flights are captured in the digital model rather than left to a note.

Our view on RC stairs

We embed civil and structural engineers in UK consultancies, and stairs are a good example of a task that looks small and eats time. A stair is rarely the headline of a project, yet it appears on nearly every multi-storey scheme, and it comes back at the worst moment: the architect revises a floor-to-floor height, the rise changes, and the slab thickness, loads and bar schedule all move.

Here is how we handle that:

• We build the calculation so geometry is a single set of inputs, and the slope factor, loads and reinforcement update with it.
• We state the support assumptions on the first page of the calculation, so the reviewer can challenge them before reading anything else.
• We keep the calculation, the drawing and the model aligned to UK standards and Eurocodes, so the package arrives review-ready rather than as three documents that disagree.
• Your client relationship stays with you. We work inside your workflow and under NDA.

For a consultancy short of capacity, the benefit is not a clever stair. It is a reliable one, delivered without a permanent hire. Our calculation and drawing review workflow shows how that handover works in practice.

— Mohammed

When to hand stair design to an embedded engineer

It makes sense to bring in outside capacity when:

• several cores or stair flights need designing at once and your team is committed elsewhere
• the calculations are done but the reinforcement drawings and BIM objects are behind
• changes are arriving from the architect faster than you can reissue calculations

We provide remote engineering support for UK consultancies, with project kick-off within 48 hours, and our CAD and BIM services cover rebar detailing for the stair drawings. If your need is the design itself, our structural engineering page sets out the scope, from reinforced concrete to steel, timber and foundations. To see how we compare with engaging individual freelancers, read our comparison of remote support and freelancers.

Checks before you issue

Run through this list at the end of every stair calculation:

1. Do the going, rise and pitch match the architect’s current drawing and Approved Document K?
2. Is dead load taken on the slope and imposed load on plan?
3. Is the imposed load category correct for the occupancy, not just the domestic default?
4. Does the support idealisation match the detail on the drawing?
5. Has deflection been checked with the actual reinforcement provided?
6. Is top steel provided where restraint may develop?
7. Is the Eurocode 2 edition stated?
8. Do the bar marks on the drawing match the calculation and the schedule?

FAQ

What is the minimum waist thickness for a concrete stair?

There is no single code minimum. Thickness is governed mainly by deflection, so you start from a span/depth trial and confirm it with the Eurocode 2 check. Fire resistance and cover also set a floor, and the project’s fire rating should be checked. For a domestic flight of around 3.6 m span, 150 mm is a reasonable first trial, as in the example above.

Do concrete stairs need shear links?

Often not. In a longitudinally spanning flight the shear stress is usually low, and the engineer can frequently show it is below half the concrete shear resistance, so links are not required. That conclusion still has to be demonstrated in the calculation, and it does not apply automatically to short, heavily loaded or cantilever stairs.

What imposed load should I use for stairs in the UK?

For domestic stairs, 2.0 kN/m² with a 2.0 kN concentrated load is typical, taken from BS EN 1991-1-1 and its UK National Annex. Public and institutional stairs fall into higher categories and can need much more, up to around 5.0 kN/m². Confirm the occupancy category before you fix the value.

Is a stair slab designed like a floor slab?

The principles are the same, with beams-and-slabs rules applying to bending, shear and deflection. The differences are the sloping geometry, the mixture of loads on slope and on plan, and the support conditions at landings, which are less clear-cut than in a floor.

Sources

• Approved Document K, free online version
• Staircase building regulations UK: rise, going, pitch
• UK National Annex to BS EN 1991-1-1
• Structural design of staircase: an overview (First Principles Engineering)
• BCA guidance on precast staircases
• Stair design research, Kansas State University
• Tekla Tedds 2023 product guides
• BS EN 1992-1-1:2023, NBS publication index

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