To calculate the number of steps needed for a patio, you determine the total vertical height difference between the patio level and the lower ground level, and then divide this height by your desired or maximum allowable riser height per step.
The fundamental calculation is:
Number of Steps = Total Height Difference / Riser Height
Here's a breakdown of the key factors and how to apply the calculation:
1. Measure the Total Height Difference
First, accurately measure the vertical distance from the finished surface of your raised patio down to the finished surface of the ground or landing area below. This is your total height difference.
2. Determine the Riser Height
The riser height is the vertical measurement of each individual step. Building codes often specify a maximum riser height for safety, especially for outdoor steps.
- Maximum Riser Height: As referenced, a common guideline for outdoor steps is a maximum riser height of around 17cm. Using this maximum height will result in the minimum number of steps required.
- Lower Riser Height: You can choose a smaller riser height (e.g., 15cm, 10cm) to create steps that are lower and potentially easier or more comfortable to climb. Using a lower riser height will result in a greater number of steps for the same total height difference.
3. Perform the Calculation
Divide the total height difference by your chosen riser height.
Example:
Imagine, as the reference describes, you have a raised patio that drops 40cm down to your lawn.
- Using the maximum riser height (17cm):
Number of Steps = 40cm / 17cm ≈ 2.35 - Using a lower riser height (e.g., 10cm):
Number of Steps = 40cm / 10cm = 4
Since you cannot have a fraction of a step, you generally round the number of steps up to the nearest whole number when using the maximum riser height to ensure no single step exceeds the maximum. Then, you adjust the individual riser heights slightly so they are all equal and add up to the total height.
Adjusting Riser Height for Even Steps
Once you have the total number of steps (usually rounded up), divide the total height difference by this whole number of steps to find the exact, even riser height for each step.
-
Continuing the 40cm example (using the 17cm max riser):
- Initial calculation: 40cm / 17cm ≈ 2.35 steps. Round up to 3 steps.
- Exact riser height: 40cm / 3 steps ≈ 13.33cm per step. This is less than 17cm, so it is acceptable.
-
Continuing the 40cm example (using a target 10cm riser):
- Initial calculation: 40cm / 10cm = 4 steps.
- Exact riser height: 40cm / 4 steps = 10cm per step. This is exactly the target and acceptable.
| Measurement | Value | Calculation (using max 17cm riser guideline) | Calculation (using 10cm target riser) |
|---|---|---|---|
| Total Height | 40cm | 40cm | 40cm |
| Target Riser | N/A | 17cm (max) | 10cm |
| Initial Steps | Round Up Needed | 40cm / 17cm ≈ 2.35 (Round up to 3) | 40cm / 10cm = 4 |
| Final Steps | 3 | 3 | 4 |
| Actual Riser | Calculated Below | 40cm / 3 steps ≈ 13.33cm | 40cm / 4 steps = 10cm |
This method ensures all your steps are equal in height, providing a consistent and safer climb. Remember to also consider the step tread (the horizontal depth of the step) and ensure it complies with local building codes and provides comfortable foot placement.
