Dynamic Stairs Tread Angle Issue


Hello all, I’m looking to create some dynamic stairs. I found one on the Sketchup Warehouse site, but I need it to change based on Height and Angle. I pulled apart the one I had downloaded and figured out how to get the stringers to work, but the treads don’t match the angle of the stringers. I’ve run out of brains for this problem. I’m hoping there’s someone that can help me out with this. The model I’ve attached has both versions of the stair. Thanks in advance. Jeff

Stairs.skp (872.2 KB)


Take a look at this other DC in 3Dwhse: https://3dwarehouse.sketchup.com/model/ub3d53c17-6069-4d84-84e5-2a0d9c400ed9/DC-Stair-Calculator

Have done a DC for stairs similar to the desired, but cannot be freely shared (sorry).

There’s quite a bit of trigonometry involved in getting the End/Start Angles on the Stringers.



Thanks for the reply Nino.

I need to base the stairs on the angle of the stringers and the floor to floor height. I just can’t figure out why the treads copy at a different angle.

Do you know of any way to do this?

Kind regards,




RISER HEIGHT: First, establish what is your Code’s MAX allowable height and Divide F2F by the Max-Riser Height to figure out the number of Risers Required.

Now establish the ACTUAL Riser Height Dividing F2F by the Number of Risers Required; =FloorToFloor /

TREAD DEPTH: Similarly to Riser-Height, Codes establish MIN Tread Depth. Number of Treads = NumOfRisers -1.

You now have the Horizontal (Tread Depth) and Height (Actual Riser) Displacement for the Tread Copies needed.

Keep in mind that the Starter Tread at the Bottom of the Stair is itself placed RiserHeight inches ABOVE the Finished Floor.

NO NEED to mess around with Angles or Trig to this point.


See if attached DC/SKP sheds any more light.

NinowDC StairTreadTutorial v00.skp (58.6 KB)


Stairs are defined by riser height and tread depth in both real-world fabrication and in applicable Codes.
Why reinvent the process?


As Said. [quote=“ninoalva, post:4, topic:77258”]
NO NEED to mess around with Angles or Trig to this point.


@jkoll66 is this for a single project or for a number? If single, why bother with a DC. Just design what you want from scratch. Probably faster in the long run and allows way more control.


It was requested by one of our engineers to have steps attached to a platform that maintain the same angle when the height of the platform is changed. Am I going about this the wrong way?

The stairs I found on the Sketchup Warehouse require a stair height and stair length input from the user. Not what I need.

I need stringers and handrails as well.




As Mentioned; the ANGLE is dependent on Riser/TreadDepth and remains CONSISTENT regardless of Floor-To-Floor Height. Therefore, the angle of inclination is perfectly Academic.

STRINGERS: A DC is applicable to a limited (specified) set of elements. For Example; if the Stringer is made from Steel, is it an I-Beam, Square-Tube as opposed to a Wood or Concrete Beam?

Then comes the question of the RAILINGS; are vertical banisters and posts being used or does the client wish Cable Railings that run parallel to the stringer?

The suggested DC is to be used as a “GUIDE” and does not produces the Finished Model. Design of a DC for too many Specifics may very well prove to be a “Value Drain” in terms of vested time VS saved time on a project.



I believe your engineer has some misplaced priorities.

The primary goal of stair design is … safety.
Thousands die every year and millions more are seriously injured in stair falls.

A safe flight of stairs is defined by the relationship of uniform riser heights and uniform tread depths.

Enlightened designers strive to maintain uniform riser height and uniform tread depth throughout a structure because it’s far safer than a cornucopia of riser heights and tread depths.

In order to maintain uniform riser height and uniform tread depth when the height of the platform is changed; the change in height would necessarily be constrained to increments of riser height.

Merely maintaining a set angle by varying riser height is a recipe for injury, death and litigation.



This is for visual purposes only. Not for actual construction drawings.

We purchase our stairs from a 3rd party and they come in set angles with treads and risers built to code.

Kind regards,


Think we’re saying is that the Angle is Dependent on Riser Height (and Tread Depth). If accuracy is not required for this task, then Scale-Off the One component because there’s little value in a DC.



That probably would be good enough. I just am a little OCD about things. Thought a Sketchup guru might be able to point me in the right direction and I might learn something. Thanks for all of your suggestions.



I am not a guru. But I do often design staircases. If I read your post no. 8 correctly, what your engineers meant was that the pitch of the stairs must remain constant regardless of platform (aka landing) height.

In the UK, our building regulations (aka codes) stipulate that pitches, riser heights, tread goings, and so on, fall within certain bands of acceptability. This underlines what @Geo said about the main aim of stair design being safety (actually, I would say the primary aim is to get from floor to floor, but safety is certainly up there).

Here’s how I go about designing the basics of a stairway in case it is of use to you. You will know the overall rise (floor to floor; floor to platform, whatever). You may have a maximum rise per tread. here in the UK for a domestic staircase it is 220mm. So by dividing the height by the max. riser height you can work out the minimum no. of risers required. You will have to round it up to a whole number. Then you can use that round number to divide into the overall rise and get the actual rise (if you need to know). If you draw a line representing the pitch of the staircase extending from floor to floor, select it and use Divide to divide it into the number of risers. Draw a typical tread and then copy it at each division. You now have the treads of a staircase. All you have to do then is to add other details like risers (if you have any), balusters, handrail, strings, etc.


Just to show how quickly the basics can be done:

It’s adding the detail that takes time.


Thanks Simon,

I think I understand the basics of building individual stair cases. My problem is making something a user can bring in and by changing a few attributes have something that at least looks correct to the average viewer. It doesn’t need to be super precise. Not going to use it for anything other than presentations. I’ve found a stair that works dynamically (see attachment). I would like to use it, but I can’t figure out how to have the length update automatically when the height is changed. I then decided to start from scratch, but I’m finding it challenging to say the least.
Mezzanines_Crossover_MR.skp (951.5 KB)


The component has separate inputs for overall rise and overall going (StairHeight & StairLength). There seem to be no parameter constraints, so you can create a staircase that would be unusable by using inappropriate combinations. So I would think that you need a formula that would calculate the going from a given rise. That will depend on pitch, so you might allow users to select some appropriate pitches. In short, you would need to get rid of the option to change SatirLength and introduce a Pitch option instead. Then rewrite the necessary formulae.

In the UK, the constraints on staircase design are so complex that it would probably be beyond the ability of a DC to deal with them all. I know nothing about building codes elsewhere so I can’t say whether it would be possible in your area.


Thanks Simon,

I think I’m going to build them based on Rise and Run. And maybe have a “User can see only” attribute that displays the corresponding angle. They can play around with it until it comes close to the angle they are looking for. I’m starting to think this is more trouble than it’s worth.


Proficiency with SU’s native tools yields many ways, so much faster than fiddling with a DC.