Introduction
Concrete stairs generate the same questions on every project: how many steps, how much concrete, bags or ready-mix, what the code allows. This FAQ collects the answers in one place — each one grounded in the same geometry the Concrete Stair Calculator uses: total rise, riser height, tread depth, stair width, and the triangle formula (steps × width × tread × riser ÷ 2).
If you’re starting from zero, the complete guide walks the full estimating process first; then come back here for the specifics.
Step Geometry Questions
How many steps do I need?
Divide your total rise (finished surface to finished surface) by your target riser height — no more than the code maximum, typically 18 cm (7 in) — and round up. A 120 cm rise gives 120 ÷ 18 = 6.67 → 7 risers, each 120 ÷ 7 = 17.14 cm (6.75 in). Never round down: fewer, taller risers violate code and feel unsafe.
What is the ideal riser height and tread depth?
Comfortable, code-compliant stairs typically use risers of 15–18 cm (6–7 in) and treads of 28–30 cm (11–12 in). The widely used limits are a maximum riser of 18 cm (7 in) and a minimum tread of 28 cm (11 in). Within those bounds, shorter risers with deeper treads feel easiest — think public buildings — while taller risers with minimum treads feel steep. Always confirm against your local code.
Do all risers have to be exactly the same height?
Yes. Codes typically limit variation between the tallest and shortest riser in a flight to about 1 cm (⅜ in), and for good reason: people calibrate their stride to the first step, so an odd riser is a trip hazard. Uniform risers come from one accurate total-rise measurement divided evenly — never from stacking nominal lumber dimensions.
How wide should concrete stairs be?
Residential exterior stairs commonly run 90–120 cm (36–48 in) wide. Minimum widths are set by local code (often around 90 cm / 36 in for required egress stairs). Wider stairs need proportionally more concrete and heavier formwork bracing, but they’re more comfortable and move furniture more easily.
What is stair nosing, and do I need it?
Nosing is the projection of each tread past the riser face below — typically 2–3 cm (¾–1¼ in). It adds effective tread depth, creates a shadow line that makes step edges visible, and is required by many codes within a specified range. Form it by setting each riser board back from the tread edge above.
Concrete Volume Questions
How much concrete do I need for my stairs?
Use the formula: steps × width × tread depth × riser height ÷ 2, plus 10% waste — or run the Concrete Stair Calculator. As a reference point: a 7-step stair, 1.2 m wide with 28 cm treads and 17.14 cm risers, needs 0.20 m³ (0.26 yd³) for the steps, 0.22 m³ (0.29 yd³) with waste — about 14 eighty-pound bags. The formula-explained guide derives every step.
Should I order ready-mix or mix bags myself?
Bags usually win under ~0.25 m³ (⅓ yd³, about 15 bags); ready-mix usually wins above ~0.5 m³ (⅔ yd³, about 30 bags). Between those, get both quotes — short-load delivery fees and mixer rental decide it. The cost guide prices both routes for the example stair.
Does the estimate include the landing?
No — and that’s the most commonly forgotten volume. Estimate landings separately as rectangular slabs (length × width × thickness) and add them. A 1.2 m × 1.2 m landing at 10 cm thick is 0.144 m³, which can rival the steps themselves.
How much waste should I add?
Ten percent is the standard default for stairs. Stepped formwork has many joints that can weep, so resist the temptation to use 5% — running short at the top step forces a cold joint in the most visible location.
Code and Construction Questions
Do I need a permit for concrete stairs?
In most jurisdictions, yes — exterior stairs attached to a dwelling typically require a permit and inspections (footing, and final). Freestanding landscape steps sometimes don’t, but “sometimes” is doing heavy lifting in that sentence. Check with your local building department before forming; the code-compliance guide covers what inspectors check.
Do concrete stairs need rebar?
In nearly all cases, yes: steel tying the stair to the adjacent structure (dowels), reinforcement in the landing and footings, and bars or mesh within the steps on larger stairs. Local code and soil conditions set the minimums. Rebar displaces negligible concrete, so it doesn’t change your volume estimate.
Do I need a handrail?
Most codes require handrails on stairs with more than a few risers (commonly 4+), at 86–97 cm (34–38 in) above the tread nosings, graspable and continuous. Open sides above a certain drop also need guards. Confirm heights and triggers locally — inspectors check these closely.
How deep should stair footings be?
Below the local frost line in freezing climates — that’s the entire point of a stair footing. Depths range from 30 cm (12 in) in warm regions to 120 cm+ (48 in+) in cold ones. Your building department publishes the local frost depth; the footing estimate (length × width × depth) is added to the step volume.
Quick Answers
Can I pour concrete stairs myself?
A small straight stair (under ~0.5 m³ / 30 bags) is a realistic DIY project for someone comfortable with carpentry — the forming matters more than the pouring. Larger, curved, or structural stairs are pro territory. See the DIY vs pro guide for an honest assessment.
How long does it take to build concrete stairs?
A DIYer typically spends a day forming and a day pouring/finishing a small stair, plus a week of curing before heavy use. Pros often form and pour a simple stair within two days. Add footing excavation time in frost climates.
When can I walk on new concrete stairs?
Light foot traffic after 24–48 hours; full loading after about 7 days; full design strength at 28 days. Keep heavy point loads (moving furniture, equipment) off for at least a week.
What concrete mix should I use for outdoor stairs?
Air-entrained concrete rated for exterior exposure — commonly 4,000 psi (C30 class) in freeze-thaw climates. Confirm the exposure rating with your supplier.
Why do my new stairs show rough patches on the risers?
That’s honeycombing from air trapped against the riser forms. It’s cosmetic if shallow, structural if deep. Prevent it by consolidating each step during placement; repair shallow cases with a compatible patching mortar.
Related Guides
- Concrete Stair Complete Guide — the full estimating walkthrough.
- Cost Guide — bags vs ready-mix pricing for the example stair.
- Code Compliance — permits, inspections, and the limits behind these answers.
- Estimating Guide — the measuring workflow step by step.
- DIY vs Pro — whether to tackle the project yourself.
- Material Guide — mixes, rebar, and formwork specifications.
Get Your Number
Questions answered, the next step is arithmetic: measure your total rise between finished surfaces, choose a tread depth, and run the Concrete Stair Calculator to get your volume, waste-adjusted total, and bag count. Bring those three numbers to your supplier or contractor and the quoting conversation becomes straightforward.
Disclaimer: Calculator results are planning estimates based on the dimensions you enter. Actual concrete requirements vary with site conditions, formwork accuracy, and mix design. Verify volumes with your supplier and consult a licensed professional or your local building authority for structural or code-related decisions.
