Spiral Stairs

[Steve_Stafford]

Okay I realize there are limitations to stairs in that a spiral stair built around a post isn't "possible"?? If I'm wrong, I'm happily wrong, but there are no hits on the help search for "spiral stair"...no hint of it other than changing the boundary to an arc...etc.

I messed around with a tight spiral using intermediate levels to "continue" a stair up using the multistory option but that was fairly unsatisfactory.

So how are folks dealing with these animals? In place families?
Has anyone setup a parametric family using an array both vertically and radially? Guess not huh? I'd tackle it if only to say I did, except I'm not a mathumagician...

I've got a spiral stair to contend with now...so I'm all ears!! (well not really, I've only got two like most everyone I know...)

[beegee]

It would certainly be an interesting challenge to make a proper family.

You would need to set up a formula that calculates the number of risers between levels, based on maximum and minimum limits, ( logical operators ) converts that to an integer and then feeds that to the radial array. The radial array would need to return over itself as well ( in most cases .)

I'm pretty sure that Revit can't handle that sort of formula (yet.)

I suggest an in-place is TWTG.

PS. Disregard the part about the risers. You can set up parameters to give the correct number quite easily. Its the next bit thats difficult !

[shaunv68276]

I do a number of spiral stairs. All around a 100mm RAD column, 1m wide
Varies from 180 deg to 360 deg and multi level with no problem. I do have a sprial stair training avi that helps if you need it as well as the working example

[Steve_Stafford]

Thanks for sharing , I'll take a look a soon as possible this morning! How big is the AVI? May be worth seeing that, let you know.

[Steve_Stafford]

Okay since I said it can't be done I might as well qualify my statement and post an image of what "can" be done to graphically convey the intent to provide a spiral stair as opposed to modeling the "true" stair.

Spirals tend to be (in the US according to our graphic standards books) one of three common angles and to do a typical stair often requires the boundary to overlap itself. Revit won't allow this overlap so you must alter the real tread angle so the total treads will fit within 360 degrees.

The attached image depicts a stair that normally would travel 405 degrees but I reduced the tread angle to 23 degrees, from 30 to fit the treads within 360 max. As a graphic image it's okay, but one couldn't expect to do shop drawings from it...so a builder wouldn't be satisfied. Also the true landing relative to the first riser isn't necessarily accurate either. So some "cover thy bottom" notes are required to clarify where a stair must start and or end depending on your situation.

This is my understanding...

[christo4robin]

Steve,

Just a thought--can you do anything with unusually large nosings to get the overlap you're referring to?

Christopher

[Steve_Stafford]

The overlap I'm talking about isn't a stair tread overlap, rather the overall travel of the stair. If you consider the 9'-0" floor to floor of the image I posted. That stair technically starts and ends 405 degrees later based on "real" treads. But Revit will only let you model a stair that fits in less than 360 degrees. So 30 degree treads must be whittled down until they "fit". The stair looks convincing but if you were to actually walk up it, you'd find it a bit uncomfortable because each step would be too shallow for your foot at the center of travel.

Make sense?

[PeterJ]

Steve

Couldn't you work out what ten risers was (80" maybe?) and then make a stair that started at level zero rose to 80" and a second stair that rose from 80" to level 1?

Presumably you don't schedule stairs so you wouldn't cause a problem there but it would give you a model that could form the basis of the carpenters, or the steel fabricators, rods.

It would seem an okay workaround for the moment.

Pete

[Steve_Stafford]

I did try something similar, I added a mid level @ 5'-0". Then made one stair rise to mid then another to rise from mid to top. But bottom stair stops on tread below the mid level and the top stair starts on tread above the bottom which leaves a tread "missing". Ungainly no matter how you slice it.

The stair tool needs to be able to draw a spiral based on rise, tread size, angle rules and the post diameter just the way you'd lay out one for real.

[beegee]

I've played around with making a parametric family until my limited supply of time and patience is exhausted. I cannot get a combined radial and vertical array to work properly.

I'll leave that for those clever parametric family builders out there.

I quite agree with Steve that this should be part of the standard stair tool package.