by Dennis Collin
A common question about stairs is the creation of a stair that has a quarter winder or similar. This is followed up with how to control the winder point as Revit’s default winder option doesn’t produce a stair that you would expect to find within the UK.
Fig 1. Changing the winder style property of a stair run to single point.
To produce a compliant stair winder, users need to set the component stair winder type to a point rather than the default ‘balanced’ style. Alternatively, the winder stair can be drawn as a sketch with riser lines position to suit. I tend to work with the former option as the component stair can always be converted to a sketch, which saves time. However, it will also be necessary to edit the sketch lines to ensure that the stair modelling tool does create valid and acceptable geometry! Using the default method also results in the railing tool reporting that it cannot create continuous rails due to the extreme drop in height in such a short distance!
Fig 2. Expect error messages with single point winder type or bespoke stair construction!
Since the stairs are the more important of the two and to make the task easier, I recommend not creating railings initially, focus on the stair modelling first and then worry about the railings later!
Fig 3. Due to the nature of a single point winder, Breaks occur with railings and stringers.
With the railings absent, convert the component stair to a sketch-based item. If the element is already sketched based, choose edit sketch. Sketch based stairs are more flexible for other bespoke situations, such as varying tread depths and risers on existing stairs.
Fig 4. A straight line (1) is inflexible, whereas a series of line segments (2) can follow the intended route.
To understand the problem, we need to think about the nature of lines. If a line is composed just of 2 vertices, a start point and an end point, the geometry is too rigid to cope with a sharp bend (or stair!), but by splitting sketch lines, thereby adding vertices, the line becomes more flexible and can adapt better to more challenging situations. A bit like a ‘Slinky Spring’!
Fig 5. A modified stair sketch with strategic split points to aid in flexibility to model railings and stringers/supports.
By default, the sketch boundary lines will try and guess how they should adapt in the change in height from the stairs base level and its height constraint. Depending on the modelling situation this behaviour can be changed on a segment-by-segment basis ‘slope’ or ‘flat’ rather than the normal ‘Autodetect’ setting.
Fig 6. Editing sketch boundary lines to model a point-based winder stair.
This can take some experimentation depending upon the model constraints and stair type, but by focusing on the stair and getting the model looking right, the railing elements can be added on after and they will deform to the host stair object.
Fig 7. Checking railing family connection and height adjustment settings.
If an error message appears relating to railing continuity, check the railing type properties, possibly add a landing height adjustment and adjust rail connection settings as appropriate.
Fig 8. Single point winder stair with continuous railings and winders with no error messages or warnings!
The railing sketch will mimic the stair sketch, but if necessary, the railing sketch can also be adjusted to suit, by using additional split operations and segment sloping options which work like the stair boundary sketch lines. Hopefully with a few checks and adjustments an acceptable winder stair should result, along with some appropriate railings.
Fig 9. Railings have similar options to control tightly sloping paths.
In summary, stair and railing families are some of the more complex Revit families, with settings and controls that are several levels deep in terms of dialogue boxes. Stair and Railing elements are a popular topic of discussion on Cadline’s follow-on and bespoke training courses. For more details visit https://training.cadline.co.uk/ and talk to one of the team who can help you with your requirements.