Balanced Stair Ergonomics - Overview Tab
The Overview tab consists of several parameters that directly affect the resulting stair layout, based on the background calculations under the automatic mode. These parameters are driven by your initial inputs and some default system settings, including the priority and constraints to the rise and going values, based on the 2R+G (Blondel) formula.
The Blondel Formula
The formula was developed by François Blondel, a 17th-century French architect who recognized the importance of comfort in stair design. His approach became a foundational guideline in architectural stair planning. "François Blondel, a 17th-century French architect, understood the importance of comfort in stair design. He developed a formula, known as the Blondel Formula: 2 Risers + 1 Tread = 25 inches (63-65 cm). This formula is a golden rule in architecture, helping architects calculate stairs that are pleasant to walk on".
The Formula
2 Risers + 1 Tread = 25 inches (63–65 cm)
For more details, see: Understanding the Geometry of a Comfortable Staircase
Below is an explanation of the parameters and options available in the Overview tab. The values shown are based on the sample stair geometry.
Balance Stair –Overview tab
Available Parameters
- Automatic fit: This checkbox enables the fully automated creation of the stair with the arrangement based on the calculation method applied by default. It is checked by default. If you uncheck it, the corresponding options and parameter fields below will become active.
- Priority: This combo box allows you to select the priority used in the stair calculation method - Rise, Going, or Stride. These values correspond to the input fields shown below.
The combo box is active only when Automatic fit is checked. If unchecked, it will be greyed out.
- Rise: The vertical height of the tread.
- Stride: The resulting value from the Blondel formula (2R+G).
- Going: The horizontal distance of the tread step. It is not the overall tread depth, as this may also include an overlap element.
- Total tread number: When active, you can change the tread number using the up and down controllers or by entering a number directly. Changing this value will reconfigure the stair arrangement and change the other values in the corresponding fields.
- Rise: When active, this defines the vertical distance of the tread pattern. Typically, it is driven by the number of treads from the calculation. You can adjust this value. When the value is changed, the stair will recalculate to the nearest value that will give a whole number of treads, from the overall geometry of the stair.
- Going: When active, this defines the horizontal distance of the tread pattern. Typically, it is driven by the number of treads from the calculation. You can adjust this value. When the value is changed, the stair will recalculate to the nearest value that will give a whole number of treads, from the overall geometry of the stair.
- Stride: The field is greyed out and inactive. It displays the resultant stride value from the stair calculation based on the inputs from Rise and Going.
- Pitch angle: The field is greyed out as it displays a resultant value from the calculation method. It provides the incline angle of the stairs for reference only.
- Pitch: The field is greyed out and inactive. It displays the resultant pitch angle of the stair from the Rise and Going inputs, which form the triangle. The value displayed is tangent. Using the inverse tangent will show the angle in degrees, via an external calculator and match the previous pitch angle field.
- Pitch value is a tangent value: Pitch (Tan X) = opposite/adjacent
- Example: Tan x = 170/290 = 0.586 rounded up to 2 decimal places 0.59
Changing the number of treads, rise or going values will influence how the cell text is displayed. If the result value falls outside the given constraint, the text will be highlighted in red to alert you that the value exceeds a constraint value from the constraint table.
Balance Stair - Stride exceeds the constraint
from the constraints tab
Read next about the Balanced Stair Definition - Ergonomics - Constraints Tab