!Restored: Flaw in stair logic

[Anonymous]

The problems with the stair tool stem from a flaw in the logic. The stairs are being defined by where the riser is rather than where the front edge of the stair tread is.

In this post I've attached an image showing a stair that does not have a nosing overhang:
- the 3D matches the 2D; and
- the handrail is the correct height above the nosing of the stair (as stipulated by regulatory requirements).

In the subsequent post I will attach an image of the same stair with a 30 nosing overhang:
- the 3D no longer matches the 2D; and
- the handrail is no longer the correct height above the stair nosing.

These problems occur because the 3D of the stair is being generated by the outside face of the riser rather than the front edge of the tread. The nosing overhang is being added to the front edge of the tread instead of at the back where it should be, with the riser face moving back by the distance of the nosing overhang.

In the real world stairs are set out by their treads, not the risers, and the locations of all of the other elements of the stair is determined relative to where the treads are located.

I'm really surprised that a program as mature as Archicad 11 contains such a fundamental flaw in its logic. It is not reassuring.

[Laura Yanoviak]

Bricklyne wrote:
Good thing you're in architecture; no laughs required here......

Actually, I've found the profession requires a sense of humor...

[Thomas Holm]

mikem wrote:
In this image of the same stair with a nosing overhang. Note how the additional tread width has been added in front of the riser rather than at the rear of the tread with the riser moved backwards.

This behaviour must create havoc on winder stairs with the consequence being that they are not modelled correctly.

Mikem, I fully agree that Stairmaker has its problems, however if I were to decide, I wouldn't want the nosing parameter to add anything to the tread depth. I'd just like it to move the riser backwards.

Also, you will find a better plan view representation of the stair with nosing if you check your settings. With a plan scale of 1:50 or greater, and scale sensitivity on, it will show a nosing too.

And in AC12, 2D plan representation of railings work. Stairmaker has got an update. Far from perfect, it is much better than before, and I will continue to use it as a huge help when designing stairs. I would not recommend using it without consciousness and caution, though. You always have to know your tools.

[Anonymous]

Mikem, I fully agree that Stairmaker has its problems, however if I were to decide, I wouldn't want the nosing parameter to add anything to the tread depth. I'd just like it to move the riser backwards.

Stairs are measured nosing to nosing here in the USA and the guardrail is measured at 42" vertically from the tip of the nosing. If the guardrail is set back an inch from the nosing, then it's too low and there's problem. Archicad should reflect that. If it doesn't...

[Thomas Holm]

william235711 wrote:

Mikem, I fully agree that Stairmaker has its problems, however if I were to decide, I wouldn't want the nosing parameter to add anything to the tread depth. I'd just like it to move the riser backwards.

Stairs are measured nosing to nosing here in the USA and the guardrail is measured at 42" vertically from the tip of the nosing. If the guardrail is set back an inch from the nosing, then it's too low and there's problem. Archicad should reflect that. If it doesn't...

Sorry, I wasn't clear. By tread depth I meant the nose to nose distance. The nosing parameter shouldn't change that, it should just push the riser further back like you said. That of course adds to the actual material width of each step, but it should not affect the flight length. And it doesn't in Stairmaker. I haven't tested the guardrail issue though, we have a couple of different standards here in Sweden. It's quite possible to change the height to what you want, in Stairmaker. And in AC12 a few other long-standing Stairmaker problems are gone.

[Anonymous]

Mikem, I fully agree that Stairmaker has its problems, however if I were to decide, I wouldn't want the nosing parameter to add anything to the tread depth. I'd just like it to move the riser backwards.

This isn't consistent with how plan sections are cut. If we cut the wall 5 feet above the floor, then everything we look at below should be consistent. This is the 2-d/3-d bifurcation that drives me crazy about Archicad. It should be consistent. The steps should be drawn as you see them from above from nosing to nosing. And where are the railings? I need to show the plan examiner guys that I have 36 inches (or more) of clear exit width.

Wm

[Thomas Holm]

william235711 wrote:
And where are the railings?

In AC12, as I said.

[Anonymous]

B067050: Stair definition logic is wrong

Can one of those who already have Archicad 12 check and confirm if this logic flaw has been corrected, and post similar images to demonstrate that it has been fixed.

[Laura Yanoviak]

mikem wrote:

B067050: Stair definition logic is wrong

Can one of those who already have Archicad 12 check and confirm if this logic flaw has been corrected, and post similar images to demonstrate that it has been fixed.

Does this help? I've exaggerated the nosing for effect.

[Anonymous]

Laura:
- when you add the nosing does the riser face move back so the tread stays where it is or does the nosing get added to the front of the tread? If it is the latter then the logic is still wrong and it will throw winder stairs out.
- does the 2D now match the 3D?

[Anonymous]

You're right, Mike. I don't winders very often but there's an issue if that's how it handles it. Does someone know?

And what does the 2-d look like? It's important that Archicad consistently work through an idea. That's why it should cost $4k, right?