What Ifc Product does a ladder belong to?

After a brief look, I would assume that ladders should be set to be IfcStair. Can anyone confirm this or is there another type of IfcProduct that it should be instead? I see no explicit mention on the stair documentation page that it is the correct type. I also do not see any clarification on the IfcStairTypeEnum that allows me to describe it as a ladder.

a ladder that is not a permanent built-in component, like a stair, shouldbe considered as a discrete accessory.
See http://www.buildingsmart-tech.org/ifc/IFC4/Add2TC1/html/link/ifcdiscreteaccessory.htm

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Thanks. Most ladders are metal and bolted in in a way that is “permanent”, but theoretically I guess it can be unbolted (but then again, so can any steel bolted connection). So therefore my conclusion is that it is an IfcStair, unless it is meant to be a moveable non-built-in component, in which case I will make it an IfcDiscreteAccessory.

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I have defined it in one project as a IfcStair. In the end it is an element used for a vertical connection between two stories.

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There is a differecne between an IfcStair and an IfcStairFlight.
A ladder is an ifcStairFlight. “[Assembly of building components in] a single “run” of stair steps (not interrupted by a landing). …”

IMO, you should only use IfcStairFlight if you model the whole stair container and then assign IfcStairFlight to each one of the single “runs” of stair steps not interrupted by a landing, as you said.
If your goal is to model a ladder, then IfcStair seems more convenient, as the whole object (container).

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Looking at the Type Use Definition, there is no direct reference to a ladder, but the ones mentioned seem like smaller elements in comparison (sub-elements in a larger element if you will). Perhaps the use of IfcDiscreteAccessory can be further explained in the ongoing IFC4.2 work?

I don’t think this is correct. The entity should always be IfcStair, and IfcStairFlight is specifically the rising part of the IfcStair. I think this is backed up by the properties, such as RequiredHeadroom in Pset_StairCommon and (actual) Headroom in Pset_StairFlightCommon. But please correct me if I am wrong.

@TLiebich once this discussion is resolved, perhaps it is best to explicitly mention the usecase of a “ladder” somewhere in the IFC spec, to prevent further confusion?

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I’d like to bump this thread and propose that LADDER be added as a PredefinedType to IfcStair for fixed ladders.

Again bumping this thread, as yet again I am dealing with this issue in models. My current policy is to mark them as IfcStair.

@jwouellette - who, in buildingSMART, would have the final say on this matter and can add it to the schema / documentation to prevent further confusion?

@AlexBradley-CUBIM - I understand that the Ports and Waterways extension will address this (as fixed ladders are a safety critical asset in this domain)?

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@Moult, the current draft Model that will be release in the comming weeks for candidate standard vote includes the addition of Ladders via a PDT LADDER on the predefined type of IfcStairs

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Thank you. This issue is now resolved - I will wait for the release. Is there a place to see this candidate, as well as the drafts that went into developing it that isn’t behind closed doors? That way, the community could also comment.

For those interested, IFC4x3, which is now released, includes LADDER as promised. Great job!

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How would a ladder such as this one be modeled in IFC 2x3?

According to the specification of IfcStair each flight should be an IfcStairFlight, and the landing should be an IfcSlab, but I’m wondering if a metal landing such as the one in the picture can be considered a slab.

https://standards.buildingsmart.org/IFC/RELEASE/IFC2x3/FINAL/HTML/ifcsharedbldgelements/lexical/ifcslab.htm

"IfcSlab

Definition from buildingSMART: […] A special type of slab is the landing, described as a floor section to which one or more stair flights or ramp flights connect. May or may not be adjacent to a building storey floor. "

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