Can't change dimension segment to this value error.

[Anonymous]

I have used these forums an others for years now, and this is the first time I've been unable to find an answer.

This is a random issue (as far as I can tell), where I select an object and click on the dimension value, type in the new value I want it to have, press 'Enter':

"Can't change dimension segment to this value."

This has happened with model objects, reference planes, and design lines. The only thing that seems consistent is I'm usually in a plan view when it happens (but that's where I spend most of my time anyway).

Sometimes the problem is solved by shutting down and restarting, other times it persists through that. I have deleted the element and redone it only to get mixed results, sometimes its fine, other times it's still an issue.

Google pulls in a handful of hits for that exact error, but none of them have been helpful.

I have only been noticing it for the past ~12-18 months, but it's starting to get to me. I would really appreciate some help.

Thanks

[martijn_pater]

Just copy the element entirely, delete the constrained one, if you have lost dimensions place them back.

[Lance.Coffey · Accepted solution]

@sgonz3189WXKS I suspect that there are multiple issues leading to this error.

However, one that you could readily encounter (and avoid) is if you are moving the witness lines to the Cut Edge of a wall.

When Tab selecting for the different portions of the wall, watch the Status Bar, and make sure that you are not selecting the Cut Edge.

Here is a video showing this situation (I also mentioned some other items to check at the end). 

[martijn_pater]

@Lance.Coffey Nice explanation video. Still I think copy/deleting the wall or element could work a lot faster then trying to figure out where it might be constrained to the cut edge or otherwise, probably depending on some integrated modeling aspects though. That might not always work out I suspect. Kudo's for the video.

[Lance.Coffey]

@martijn_pater I think we may be talking about different things.

The Cut Edge issue described in my prior post/video isn’t related to a constraint, but to how the dimension witness line is placed.

If the Witness line is placed or moved to the Cut Edge face of the wall, then that dimension (permanent or temporary) can no longer drive the position of the wall. Other dimensions placed on the same wall (but not the cut edge) could still do so.

Also, the behavior between temporary and regular dimensions is different:

Temporary Dimensions: Error: Can't change dimension segment to this value.

Regular Dimensions: When selecting the wall, the associated dimension text does not turn blue and you can’t click to change the value (to move the wall).

I agree that for issues related to constraints, cutting the wall to the clipboard and then pasting back to the same place (similar to what you mentioned of copy/delete) should remove constraints (and associated dimensions) for the wall allowing it to move freely.

[sojedaC7A32]

I was happening to me when editing a part of a family that I created, more specifically I was editing the sketch of an extrusion, the error kept showing up (Revit 2023).
What did the trick was this, the family was made of several Extrusions that I JOINED together, the problem stopped when I UNJOINED all the solids, note that there were no Constraints in the model not even hidden constraints and the problem kept showing up, I only stopped after I UNJOINED everything.
Note that It only worked after Nothing was joined with nothing else, I tried unjoining first the extrusion that was giving me problems and the problem persisted, I hope this helps someone.

[mdamirulfaiz.kalana]

I notice that problem also in these days. but it seem just an easy fix.it happens when i want to move an element in model to a new location bu inserting a new dimension. these will pop it. my solution now is just reopen the revit file 😅

[jesse3WLUJ]

I have also been getting this error message for years, and still get it in Revit 2024.2.  I am getting it right now when trying to specify a dimension from a grid line to the edge of a window.  It's always lies.  You can change the dimension to the value, you just have to find a different way to do it.  Really annoying bug, would be great to fix one day, ideally before Revit 2030.