Stair design is a critical and often complex part of structural engineering and architecture. It blends architectural vision with structural integrity, code compliance, and ergonomics. While specialized software exists, Microsoft Excel remains an indispensable tool for quick calculations, preliminary design, verification, and creating organized, reusable checklists.
A complete stair design project typically relies on a suite of interconnected Excel sheets. Here is a breakdown of the most crucial ones.
The Stair Geometry and Proportion Calculator
This is the foundational sheet where the basic layout is determined. It ensures the stair is comfortable and safe to use by adhering to ergonomic rules and building codes.
- Floor to Floor-to-floor height is the total vertical rise.
- Desired/Restricted Stairwell Length is the available horizontal space.
- Building Code Requirements are the Minimum/Maximum values for riser height and tread depth (e.g., as per International Building Code, OSHA, or local standards).
Calculations & Outputs:
- Number of Risers:Â
=ROUND(Floor Height / Assumed Riser, 0)Followed by iterative adjustment. - Actual Riser Height:
=Floor Height / Number of Risers - Number of Treads:
= Number of Risers - 1 - Tread Depth (Going): Calculated based on available horizontal space or using rules of thumb like Blondel’s Formula.
- Blondel’s Formula Check:
(2 * Riser) + Tread. The result should fall within a comfortable range (typically 600mm to 630mm). - Total Stair Run:
= Number of Treads * Tread Depth
The purpose is to quickly iterate between different riser/tread combinations to find the most optimal and code-compliant layout before proceeding to structural design.
Structural Design of Stair Slab (Waist Slab) Calculator
This sheet performs the structural calculations to determine the required reinforcement for the stair slab, which can be designed as a simply supported or continuous “waist slab.
- Material Properties: Concrete Grade (e.g., f’c), Steel Yield Strength (fy).
- Loads: Finishes (kN/m²), Imposed Live Load (kN/m² as per code), Parapet/Wall load.
- Geometric Data: Effective span of the stair, thickness of the waist slab, riser & tread dimensions.
Calculations
- Load Calculation:
- Self-weight of the waist slab (based on its thickness and slope).
- Self-weight of steps
= (Riser Height / 2) * Concrete Density. - Total Dead Load (DL) and Live Load (LL).
- Factored Design LoadÂ
Wu = 1.4*DL + 1.6*LLÂ (Factors may vary by code.)
- Bending Moment (M):Â
= (Wu * Span²) / 8 For a simply supported. - Main Reinforcement:
- Calculates the required area of steel (As) using the standard flexural formula.
- Suggests a suitable bar size and spacing.
- Shear Check: Ensures the concrete slab can resist the maximum shear force without requiring shear reinforcement (in most common cases).
The purpose is to size the structural concrete element and determine the main tensile reinforcement.
Stair Reinforcement Detailing & Bar Bending Schedule (BBS)
This sheet translates the calculated reinforcement areas into practical, executable details for the site. It is often linked directly to the Structural Design Calculator.
- Required area of steel from the Design Calculator.
- Standard bar diameters (e.g., 10mm, 12mm, 16mm).
- Geometry of the stair (lengths, angles).
Calculations
- Bar Selection & Spacing: Determines the number and spacing of bars.
- Cutting Lengths:
- Main Bars: Calculates the total length along the slope, including development lengths at supports.
- Distribution Bars: Calculates lengths for the transverse reinforcement.
- Additional Bars in Landings: Specific lengths for landing areas.
- Bar Bending Schedule (BBS) Table:
- Bar Mark | Description | Diameter | Number of Bars | Cutting Length | Total Weight
- Total weight of steel required for the flight.
The purpose is to generate a clear, concise schedule that the steel fixers can use to cut, bend, and place the reinforcement, minimizing waste and errors.
Stair Load on Supporting Beams Calculator
This sheet calculates the reactions from the stairs to ensure the supporting beams or walls are designed adequately.
- Total Factored Load (Wu) from the Structural Design sheet.
- Span of the stairs.
Calculations
- Reaction at Supports:Â For a simply supported case.
- Load per Meter: The reaction is presented as a line load (kN/m) that acts on the supporting beam.
List of all Excel sheets of Stair Design
Updated on 08/01/2026. New sheets will be added soon!
