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FlexStairs Icon


Basic Workflow

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

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

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

4.  Customize the Nosing, Tread Returns, Tread Thickness, Stringer Thickness etc.


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.


📌 To zero out a component setting you must type in 0, and then apply the change.  Using Back Space or Del only, without typing 0, will cause the dynamic component to have an error and it won't behave as expected - This is due to a bug in Sketchup's Dynamic Components extension.

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 the Comfort Relationship setting is fixed to 62 cm* (All other 'Fixed' settings are set to 0).  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

One Click Landing

You can easily add a landing to the staircase with one click with the 'Interact Tool'.

One Click Landing
Add/Remove a landing with one click.

📌 By default the length of the landing is equal to the width of the steps.  You can change the length by setting it to anything other than 0.

Remove The Top Step

In many situations you may find that the top step should be the finished floor.

Set 'Remove Top Step' to ON and the last step will be removed.

Removing The Top Step
How to remove the top step

Set Stringer Thickness

You can choose to set the stringer thickness by measuring the Minimum Thickness from the tread (AKA Waist or Throat) or to set the thickness according to the thickness of the top and bottom floors.

Stringer by Minimum Thickness (Waist/Throat)

Stringer by Minimum Thickness
Stringer by Minimum Thickness

Stringer by Floor Thickness

Stringer by Floor Thickness
Extend by Floor Thickness

Extend Stringer to Meet Floors

You can extend the stringer up and down so it meets the floors nicely.

Extend To Top Floor

Extend Stringer To Top Floor While Thickness Set By Waist Measurement
Extend to Top Floor - Stringer by Waist

Extend To Top Floor With Top Step Removed

Extend Stringer To Top Floor and Hide Top Step

Extend To Bottom Floor

Extending FlexStairs to the Bottom Floor
FlexStairs Extend to Bottom

📌 Notice that in the above example there is no need to extend the stringer to the top floor because it meets it exactly.  It's thickness is set to: '(B) By Floor Thickness'.

Cut Openings Through Floors

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

[FlexStairs with WallCutter Animation]
FlexStairs with WallCutter

Make Sections With Sketchup Section Cuts

FlexStairs are optimized to work with Sketchup 2019's improved section cuts.

📌 For Sketchup 2018, the sections may not close properly by default.  You can however get the sections to close if you un-hide all hidden geometry within each of the steps.  You can do this in two clicks with Tomasz's Unhide All v2.0 plugin.

FlexStairs Section Cuts
Section cuts in a stairwell that took no more than 5 minutes to model!

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 . . .

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.

Spiral Stairs with TrueBend


You can use ThomThom's free TrueBend extension to twist FlexStainrs into a spiral staircase in just a few clicks.  Don't forget to Zap the stairs beforehand or else components might start flying all over the place 🙄


FlexStairs with TrueBend