Basic design continued
- General stair parameters and optimisation
- Headroom control feature
- Modifying winders
- Adding landings
On the previous page we covered how to set up an initial stair project.
We will now move on to some key elements of optimising your project so it’s safe and easy to manufacture.
General stair parameters and optimisation
Please watch this video for an overview on how to adjust the overall dimensions of the stair, and a quick reminder on selecting individual parts.
We then edit the number of risers (steps) and highlight the impact this has on the riser height and tread width.
The Stair Rule
The video refers to the Stair Rule which is at the heart of StairDesigner. Meeting the Stair Rule indicates that the stair is safe to walk up and down.
The Stair Rule value = 2 x riser height + tread width.
The tread width, also known as the going, is the distance between one step nosing and the next along the treadline.
A narrow tread width can make for an unsafe stair, as can a large riser height.
The treadline (shown in the 2D design window) is an imaginary line that runs along the leading edges (or nosings) of the stair treads, typically at the front edge where each step begins. It traces the path a person’s foot follows as they ascend or descend the staircase. The treadline is important for calculating and maintaining consistent step dimensions ensuring the stair is safe and comfortable to use.
StairDesigner calculates the Stair Rule, riser height and tread width automatically, and will show the value in red and a warning symbol if they fall outside minimum and maximum control values.
Below we can see a warning for the Stair Rule:
Note that the Stair Rule, riser height and tread width values are greyed out, this is to indicate that they are not editable.
The control values can be viewed and modified in Tools menu > Control values:
This configuration makes it fast and easy to adjust the stair, typically by changing the riser/step number (shown in blue), or other parameters like the flight length, to meet the Stair Rule.
It may not be possible to meet all control values simultaneously. It is then a case of seeking the best compromise to meet your project requirements, balancing how steep a stair is with the available space.
Extra note: Nicolas-François Blondel
Nicolas-François Blondel (1618-1686) was an architect and the first to identify a relationship between the riser height and the tread width.
He determined that a comfortable step length (tread width) was double the riser height and about 62cm.
The Stair Rule was originally called the Blondel Rule, and set control values of between 60cm and 64cm.
It has been suggested that due to the average height increase of the human body, the values should now be 62cm and 66cm.
Headroom control feature
StairDesigner includes a headroom control feature that allows you to confirm the safe passage up to the next floor level.
Specifically it measures the distance between the step directly below the stairwell opening and the height of the opening. If the distance is less than a customisable control value, a warning will appear in StairDesigner.
So, how does it work?
Add well hole (stairwell) parameters
In the Modify menu tab select the Well Hole option.
This will open another window where you can set the required dimensions of your well hole (stairwell), plus importantly the floor thickness.
Once confirmed StairDesigner will show in green the well hole position on top of the stair.
Control value
If the headroom distance is less than your control value, you will see a warning in the Properties menu.
The general parameters of the well hole are also shown here.
You can set your control value in Tools > Control Values.
Building regulations in different countries will vary, but an average safe passage is around 2000mm.
If you make a change to your stair the headroom is automatically recalculated, so it’s easy to check this important design point as you work on your project.
Edit well hole
You can also select the Headroom Edit button in the Properties menu to adjust the well hole.
This allows you to reshape the well hole if it differs from a general rectangle. You can add or remove points to shape the well hole and even create a curve by clicking and dragging the line.
The orange minus sign in the Headroom section of the Properties menu is used to delete the well hole.
To create a new well hole you need to start again from the Modify menu.
Include landing step in the well hole
The well hole is set to start at the nose of the landing step and this position cannot be changed. In some cases however it is useful to include this very last step.
How can we solve this?
The solution is a work around, where we add an extra landing step in a way that it will set the well hole edge at the desired spot without interfering with our output like the 3D view or the cutting list.
First you add a second landing step to your stair with the smallest possible length. In this case it is 0.1mm.
The original landing step has been positioned lower now, so adjust its height to equal that of the staircase. The height of the original landing step and the new ‘false’ landing step will be the same.
Finally set the parameters for the extra landing step as follows:
- Thickness: 0mm
- Material: Nil
- Riser: No
A Nil material can be created without any colour or structure using a 100% transparency.
Also, ensure price and weight parameters remain blank.
The result is a correct 3D view of your stair and the cutting list will indicate the Nil material clearly so that you can discard it from production. Also, the cost and material summary for the stair will not be distorted.
Modifying winders
The aesthetics, comfort and safety of a stair are closely linked to the winding.
Winders are tapered steps, their edges are not parallel to each other. The winding describes the nature of this tapering.
To maximise the comfort and safety of a stair, the winders would be tapered gradually into and out of a turn respecting the calculated tread width on the treadline. The impression when using the stair would be similar to walking up and down a straight stair.
However, it can be faster and simpler to build a stair by isolating the winding to just around the turn.
This video describes both options and how to apply and modify them.
Adjusting the winding coefficient
Two winding coefficient sliders are available, these values (default: 50) can also be modified in the Properties menu.
A higher value results in a more severe tapering of the steps.
Our video recommends modifying just the Local value but an explanation of both follows:
- Local: influences the step tapering near the inner corner of the turn
- Distant: influences the steps far from the inner corner
To adjust the default coefficients go to Tools menu > Winding:
The importance of the fixed step
In StairDesigner, the winding applies and is calculated from one fixed step to another. If the entire stair is winding, this will be the first and last step.
To apply the winding just to a specific locality, convert intermediate winding steps to fixed steps. We could select the option to convert a winding step just to a fixed step but normally we would select a straight step (which is also fixed) as shown below:
We could apply just a fixed step, this would create different winding zones that could be independently regulated with their own coefficients. This isn’t practical however in a quarter turn stair.
Note that for more complex steps – U and S shaped for example – StairDesigner will apply hidden virtual fixed steps to facilitate the calculation.
The impact on stair design
StairDesigner is always recalculating the stair in the background with every design change. Note as well the results of adjusting the winding characteristics, particularly on the stringboard.
Below is a stair with all winding steps:
And now a stair with winding steps just around the turn. The stringboard shows a greater curve near the turn.
Winding coefficient values also have an impact. A lower value will tend to produce a straighter stringboard as the steps are more equally distributed, with less severe differences in tapering between adjacent steps.
Adding landings
We will complete these basic design features with advice on adding landings. The video below provides a good overview of the options available.
So to cover the main points, landings can be added directly via selection of a model as shown in the New stair window:
To confirm some points on dimensions on this quarter turn model:
- Length of side 1 = distance from nosing of first step to the flight 2 edge of the landing
- Width of flights define the landing dimensions
Four landing models are available to choose from:
- Quarter turn (#7)
- Half turn (#8)
- Straight flight with arrival landing (#9)
- Quarter turn entrance with arrival landing (#10)
Alternatively a landing can be added to a stair that has already been created, either from a model or using the Multi-flight feature.
More information:
Essentials: multi-flight stairs
Go to Modify menu > Add a landing or click directly on the icon shown below:
The Add a landing window provides access to a range of landing configurations.
Note the Position variable, to determine whether the landing is added within the bounds of the current stairwell/flight dimensions or outside them.
Once a landing is in place, click on the landing to view and edit its parameters in the Properties menu.
The height can be adjusted, and also as shown here the length.
When adjusting the length, options are available if applicable to modify the length independently of the adjacent flights, or to ensure that the change doesn’t impact the overall the length of the stair.
Finally, please note that a stair with a landing between two flights will result in a separate set of stair optimisation parameters for each flight.
★ Tip ★
We sometimes get asked how to create a stair that starts with a landing.
Start with a stair created with the Multi-flight feature, just a single straight flight will do. Then delete this before selecting the Add a landing icon. You’ll then have just the landing, add flights to that as required.
