How to build a spiral staircase using StairDesigner

When you don’t have a lot of space to fit a stair, it’s useful to consider the option of installing a spiral stair.

This article and video will show you how to build a spiral staircase using StairDesigner, our pro level design and manufacturing software. We’ve also got a way for you to use this software without ever having to buy it.

A spiral staircase can be distinguished from a helical stair in that it evolves around a central post and the steps are supported by the post rather than a string.

Given this definition spiral and helical stairs can refer to the same stair when the inner turning point tends towards a very small arc.

The image below shows a helical or spiral stair in elm that has no central post but it moves up in a stairwell that is less than 2mx2m:

how to build a spiral staircase

A spiral staircases can be made in wood, metal or stone and can often be not only a very useful space saver but also be a great architectural design feature for a room.

Here is a stair in metal and wood:

metal spiral staircase

The very nature of a spiral staircase creates an elegant sweeping curve that can give an amazing decorative effect in any space.

Here is an example of a wooden spiral staircase we built into a small bedroom in Paris to access an attic room:

how to build a wooden spiral staircase

The downside of this type of stair is that you can’t use it for moving large objects up and down. So if possible don’t use it as the main stair of your house.

In very tight spaces a spiral staircase dimensions can be reduced to a minimum and because they can turn above themselves infinitely they can allow access to upper floors using a very small foot print.

Here is a stair that I built into a small cupboard 1m x1m, the only space left on the 1st floor to access the attic:

how to build spiral staircase

There’s no way of moving any furniture into the attic once the stair is installed though!

Because of their very regular shape, spiral staircases lend themselves well to industrial manufacturing and you will find spiral staircase kits on the market at very reasonable prices. However, problems will arise if you need a spiral staircase that doesn’t fit the standard sizes.

In this case you will have to build the spiral stair exactly to your specifications.

Knowing how to build a wooden spiral staircase with curved parts can be a challenging project even for an accomplished carpenter. However, simpler spiral stairs in square stairwells, although complex, can be less challenging.

For more information on building spiral staircases please visit our web site:

You’ll find lots of information on stair building and special techniques for building curved parts. Note that the stairs above were all built using our proprietary ‘horizontal laminates’ technique.

In this video I show how to use StairDesigner to design and build spiral stairs.

Using this process StairDesigner will provide all the working documents that will make building a spiral staircase much easier.

How to Build a Spiral Stairs: Video Audio

Hello this is Ness Tillson.

In this video I’d like to show how to use StairDesigner to design a spiral stair.

Although StairDesigner does have a specific Helicoidal stair command that can be useful in certain circumstances, this command is very limited and will not create useable manufacturing documents.

For this reason I suggest that a spiral stair be designed using the normal MultiFlight stair commands that will produce all the detailed working documents to build the stair.

Designing a buildable spiral stair using the MultiFlight stair options is fast and straightforward but to get a clean buildable design it’s important to follow a strict series of steps.

So let’s go over the basic principles and the design process…


We can see that the stair on screen has a hollow central post.

StairDesigner will not draw a circular post in MultiFlight mode but I’ll explain later how to change this post to a circular pillar and how to use the StairDesigner drawing to manufacture the post.

Let’s start a new stair and set up the parameters of the stairwell with the MultiFlight stairwell parameters dialogue box.

Let’s say that our stair is a right turning 3 quart turn that must fit a 2m x 2m stairwell .

Let’s set the first flight to 1m.

Let’s say that we would like a central post that has a diameter of 200mm.

This makes the stair width 2000 -200 / 2 or 900mm.

Let’s add a flight and give it the full width of the stairwell.

And let’s add another flight with the full width and the last flight with a half width of 1000mm.

Let’s update the stair calculations.

We can see that with 16 steps the step width and the Stair rule are too short so lets set the number of steps to 14.

With 14 steps the step height is reasonable and the stair rule is nearly OK.

Let’s click OK to accept these parameters.

If we look in 3D we can see that the central post is really a string.

Now let’s go back to the plan view to make the strings curved.

Let’s click right on the string assembly and add a curved junction.

To simulate a post of 200mm diameter, let’s make the radius 100mm.

Let’s do the same for the other corners.

Now let’s make the outside strings curved.

I use the same process making the radius 1000mm that is half the stairwell diameter.

Here’s the stair with the strings nicely curved.

However we can see that the tread line is not in the centre of the stair.

To adjust to the middle of the steps let’s change the tread line radius.

I right click the inner string curve and choose tread line radius in the menu.

Let’s set the radius at 100 + 450 or 550.

In the same way let’s adjust the radius of the other sections.

The tread line is now in the middle of the steps but we can see that the collets of the steps are still not equal. This is because we are still calculating the stair as if it had winders.

To change this lets deactivate the Winding Coefficients.

I click right again on a curve and choose the Winding Coefficients option.

I set these to 0.

I repeat on all the strings.

StairDesigner redraws the stair with equal collets on all steps.

In 3D the stair now looks like this.

We can add newel posts to complete the stair.

Now lets export the stair in DXF 3D…and we’re done.