FlexStairs Icon



Basic Workflow


1.  Scale vertically from floor to floor -  The stairs will automatically adjust.

2.  Set the Minimum Riser Height ↑ -  The total height will be divided into stairs that are either equal to the minimum or a little above it.

3.  Choose how the steps should be calculated by Fixing specific settings (🔒).

4.  Customize the Nosing, Tread Returns, Stringer Width or remove the last step in a click.


FlexStairs Terminology

📌 Satisfied with your customization?  Save aside for later use with ComponentFinder.

Need to customize further beyond what can be generated with the dynamic component?  Zap the component and edit it manually like any other component.

Fixing Settings

You can fix certain settings so that no matter how you scale the stairs component, those settings will be maintained and the stairs will be calculated accordingly.

Determine how the stairs will be calculated by choosing ONE of the following:

🔒 Total Run

🔒 Height

🔒 Comfort Relationship (2R + T)

🔒 Tread

📌 Settings marked with a 🔒 (lock) determine how the stairs are calculated.  These settings can interfere with each other so it is best to use only one of them, and keep the rest at 0!

The Fixed Width setting is not marked because it does not 'compete' with any other settings.

Fixed Total Run

You can set the Total Run for example to 200 cm (all other Fixed settings are set to 0):

FlexStairs Options - Fixed Total Run

If you then scale the component horizontally, it will snap back into place maintaining a fixed total length of 200 cm.

You can scale the stairs vertically freely.  The number of steps will change, their length and their height accordingly, while still maintaining the fixed total length of 200 cm.

[FlexStairs With Fixed Total Run Animation]
When only the Total Run is Fixed the stairs snap back horizontally but scale freely vertically

Fixed Comfort Relationship

By default all of the 'Fixed' settings are set to 0, except for Comfort Relationship which is set to 62 cm*. You can change this number to fit the requirements of your project.

FlexStairs Options - Comfort Relationship

If you scale the steps horizontally, they will snap back into place.

If you scale them vertically, they will recalculate, adding or subtracting steps if necessary while maintaining this comfort relationship between the Treads' length and Risers' height (2R+T).


📌 More about the Comfort Relationship AKA Blondel's Rule here

Fixed Tread

You can set the treads for example to 32 cm (all other Fixed settings are set to 0):

FlexStairs Options - Fixed Tread

If you then scale the component horizontally, it will snap back into place maintaining the steps at 32 cm long (+ nosing).

If you scale the component vertically, the component will add or subtract steps, each of 32 cm long, so the stairs will change both vertically and horizontally.

[FlexStairs With a Fixed Tread Animation]
FlexStairs With a Fixed Tread of 32 cm

Fixed Settings Disabled

If you set all the 'Fixed' settings to 0 you will be able to scale the stairs in all directions.

FlexStairs Fixed Settings at 0
When all Fixed settings are set to 0 (i.e. disabled) you can scale the stairs in all directions

Show / Hide The Last Step

In many situations you may find that the last (upper most step) should be the finished floor.

Simply click on the last step with the Interact Tool and the last step will be hidden.  Click again to bring it back.

Removing the last step with a click
Removing the last step with a click

FlexStairs with WallCutter

You can easily convert FlexStairs into a WallCutter component to cut through . . . Floors! 😮

[FlexStairs with WallCutter Animation]
FlexStairs with WallCutter

Comfort Relationship AKA Blondel's Rule

Blondel who? 🙄


Blondel's Rule for comfortable steps is a relationship in which:

2 Risers(R) + 1 Tread(T) = a length between a Minimum and Maximum


As long as the stairs maintain this relationship they are considered comfortable to walk on.

Riser and Tread



2R + T = Min-Max

Example ranges:

61-63 cm - Israel, Norway

61-65 cm (24" to 26") - Some states in the USA

55-70 cm (21.7" to 27.6") - (Wikipedia?)


📌 62 cm may be considered as the optimum relationship for super comfortable steps *

* Since we began working on FlexStairs (and before that) we got to step on quite a lot of different steps who's relationship varied far above and far under 62cm, and they were very comfortable . . . hmmmmm 🤔


In some countries keeping with Blondel's rule is a legal requirement!  That, along with standards for maximum angle, minimum and maximum risers, minimum headspace and more, So . . .

Make sure to refer to the building codes specific to your location!


Building codes, standards, rules and requirements vary from country to country, state to state and even city to city.

With FlexStairs there are no hard limitations.  It is very well possible to create stairs that are not walk-able and may even be illegal.  Make sure to refer to the codes specific to your location.