Here's an example to illustrate the strange behaviour I'm experiencing. A curtain wall with fixed number of vertical elements, adjust for mullion size turned on. Gray elements are standard revit rectangular mullions 600x300mm.
Now, when I replace one of the mullions with a thicker one 600x500mm, all the grids change and the curtain panels are not equal anymore, even though the width of the mullion stays the same:
Do you have any ideas what could be causing this?
Just noticed, even stranger, if you just duplicate the type of one of the mullions and not change anything, it also shifts the grid lines.
I can confirm this behavior in 2023 and 2024. With or without adjust for mullion size checked...
Pattern justification (beginning, center, end) has no bearing on the results. As soon as you change one or more mullion types Revit seems to forget how to do math.
There are plenty of ways to work around it, but it all depends on how many of them you will be placing and how dynamic they need to be after the initial placement.
I often have curtain walls that have defined patterns for early layout to give me the general patterns, but then change them to types that do not have a defined pattern (or even defined mullions sometimes), and just keep the layout when it asks if I want to convert the gridlines as independent. Then I have full control of the layout for fine tuning without pinning and unpinning all the time.
Once converted to a type that does not have a defined layout, changing the mullions does not affect the dimensions.
But this can be a pain if there are a lot of them and they are constantly changing.
-G
I think it is the result of a series of assumptions. First Revit maintains the length of the overall curtain wall while changing various properties. Second it attempts to distribute the curtain grids based on multiple possible settings. Justification at center seems to maintain the distribution of the grids outward equally but changes the first and last bay, attempting to maintain the curtain grid distribution required by the available choices, slightly different results when cycling through the spacing choices. If we expect to maintain a panel size that suggests we have to be flexible about the overall length of the curtain wall which doesn't change at all in response to different settings.
Gary's earlier reply fits my own approach pretty well. I use the pattern generating aspect of the curtain walls to get close to a desired outcome and then when that starts to get very real, I decide whether to abandon the pattern rules that are close enough for the early stages of design but no longer close enough for construction.
Edit: FWIW, I didn't check what happens if the border mullions are assigned in advance to be different sizes than the interior.
Steve Stafford
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Thanks for video.
FWIW, I believe the option "Adjust for Mullion Size" isn't meant to resolve different mullion sizes along the wall, it's meant to adjust the overall spacing to take into account the mullion size at the borders. Consider how we must adjust the curtain grid spacing to create a nominal size curtain wall door (3'-0" x 8'-0"). They probably assumed the mullions at the borders would be the same size?
Regardless I understand the way Revit responds to mullion changes isn't ideal.
Steve Stafford
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@ToanDN Looks like the rogue mullion is the same width. Try it with a wider mullion.
Steve Stafford
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@ToanDN, Not sure either, I can replicate it all day long:
unpinned and replaced a mullion with one of the same width but a different depth and here's the result. This is in 2024 but I did the same thing in 2023 when first replying.
@ToanDN wrote:
@VM_Jekabs said his mullions are of the same width but different depths.
Sigh...I misread that. *(
Steve Stafford
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