Estimate concrete volume for waist-slab or solid stairs with optional landings.
Count of risers (typical residential: 10–16)
Horizontal depth per step
Vertical height per step
Clear width of the flight
Thickness of the inclined slab
Landings
Include optional rectangular top and bottom landings.
Results
Breakdown (m³)
- Waist slab0.708
- Step wedges0.343
- Bottom landing0.216
- Top landing0.216
Notes: Waist-slab model uses waist thickness × width × sloped length + triangular step wedges 0.5 × tread × riser × width × steps. Landings are rectangular prisms. Results are approximate; verify against project drawings.
How to Calculate Concrete of a Staircase
Staircases are a vital structural and architectural feature in buildings. Concrete stair design may use a waist-slab (an inclined slab supporting the steps) or solid (mass) construction, where each step is modeled as a block. Below is a practical method to calculate the volume of concrete required for staircases, including landings, wedges, and waste allowance.
Step 1: Define Stair Inputs
Gather the number of steps (n), tread depth (T), riser height (R), staircase width (W), and waist thickness (tw if applicable). Landings require their own length (L), width (B), and thickness (t).
Step 2: Calculate Sloped Length
Total horizontal run = n × T, total vertical rise = n × R. The sloped length of the stair flight is:
Ls = √[(nT)² + (nR)²]
Step 3: Waist-Slab Method
For waist-slab stairs:
Inclined slab volume = Vwaist = tw × W × Ls
Wedge volume = Vwedge = ½ × n × T × R × W
Add landing volumes = Σ(L × B × t)
Step 4: Solid Stair Method
For solid stairs, volume is approximated as stacked blocks:
Vsolid = n × T × R × W (plus landings)
Example (Metric): n = 12, T = 0.28 m, R = 0.17 m, W = 1.20 m, tw = 0.15 m. Landings: L = 1.20 m, B = 1.20 m, t = 0.15 m.
Ls ≈ 3.92 m → Vwaist = 0.706 m³; Vwedge = 0.343 m³; landings = 0.432 m³ → Total ≈ 1.481 m³.
Step 5: Add Waste Allowance
Always add 5–10% extra to account for over-excavation, spillage, and practical site losses. This ensures sufficient supply for finishing.
Conversion Tips
- 1 m³ = 35.315 ft³
- 1 m³ = 1.308 yd³
- Concrete weight ≈ 2,400 kg/m³
Common Mistakes to Avoid
- Mixing metric and imperial units.
- Forgetting to add wedge volumes in waist-slab stairs.
- Not including landings in total calculation.
- Skipping waste allowance.
In summary: define your step dimensions, calculate sloped length, apply waist-slab or solid formulas, add landings, and include 5–10% waste. A staircase concrete calculator simplifies this process, reduces errors, and ensures accurate material planning for your project.