topic Re: Curtain wall strange behaviour when adjusted for mullion size in Revit Architecture Forum

Curtain wall strange behaviour when adjusted for mullion size

VM_Jekabs — Mon, 31 Jul 2023 08:58:43 GMT

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?

Re: Curtain wall strange behaviour when adjusted for mullion size

VM_Jekabs — Mon, 31 Jul 2023 09:22:25 GMT

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.

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Mon, 31 Jul 2023 12:19:27 GMT

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

Re: Curtain wall strange behaviour when adjusted for mullion size

barthbradley — Mon, 31 Jul 2023 13:32:32 GMT

Unpin the Grid Lines.

Re: Curtain wall strange behaviour when adjusted for mullion size

VM_Jekabs — Tue, 01 Aug 2023 06:38:33 GMT

Yes, that works, but then it defeats the purpose of the curtain wall maintaining equal spacing between mullions in case the number of elements changes.

Re: Curtain wall strange behaviour when adjusted for mullion size

SteveKStafford — Tue, 01 Aug 2023 07:53:31 GMT

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.

Re: Curtain wall strange behaviour when adjusted for mullion size

VM_Jekabs — Tue, 01 Aug 2023 08:32:13 GMT

Here's a screen recording to better illustrate what I'm talking about. Changing the mullion thickness should not affect their spacing. When grids are unpinned, changing mullion thickness behaves as expected, but then the automatic functionality of the curtain wall is lost.

(view in My Videos)

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Tue, 01 Aug 2023 12:11:50 GMT

The behavior has been pointed out, then independently verified (in multiple Revit versions and in different document files).

All we can do now is try to find the best approach (per the requirements of the project) to work around the issue and hope that someone with enough authority at Autodesk reads this and escalates it to the development team for resolution.

-G

Re: Curtain wall strange behaviour when adjusted for mullion size

SteveKStafford — Tue, 01 Aug 2023 18:38:59 GMT

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.

Re: Curtain wall strange behaviour when adjusted for mullion size

ToanDN — Tue, 01 Aug 2023 21:03:03 GMT

~~Not~~ sure ~~why~~ I can't replicate.

2022

2024

Re: Curtain wall strange behaviour when adjusted for mullion size

SteveKStafford — Tue, 01 Aug 2023 18:51:47 GMT

@ToanDN Looks like the rogue mullion is the same width. Try it with a wider mullion.

Re: Curtain wall strange behaviour when adjusted for mullion size

ToanDN — Tue, 01 Aug 2023 18:55:53 GMT

@SteveKStafford wrote:

@ToanDN Looks like the rogue mullion is the same width. Try it with a wider mullion.

@VM_Jekabs said his mullions are of the same width but different depths. If the widths are different then of course the panel sizes will be different due to the equal grid spacing.

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Tue, 01 Aug 2023 19:14:40 GMT

@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.

Re: Curtain wall strange behaviour when adjusted for mullion size

SteveKStafford — Tue, 01 Aug 2023 19:56:46 GMT

@ToanDN wrote:

@VM_Jekabs said his mullions are of the same width but different depths.
Sigh...I misread that. *(

Re: Curtain wall strange behaviour when adjusted for mullion size

ToanDN — Tue, 01 Aug 2023 20:07:12 GMT

Can you share that model?

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Tue, 01 Aug 2023 20:17:03 GMT

Sure.

I created a new 2024 file from scratch without a template and dumped the Curtain Walls into it (our template is overly bloated).

They have the problem in the new file as well so have fun 😉

-G

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Tue, 01 Aug 2023 20:19:20 GMT

BTW... If you repin that resized mullion it goes right back to where it should be.

Re: Curtain wall strange behaviour when adjusted for mullion size

ToanDN — Tue, 01 Aug 2023 20:34:37 GMT

FIFY

Re: Curtain wall strange behaviour when adjusted for mullion size

GaryOrrMBI — Tue, 01 Aug 2023 21:08:56 GMT

Interesting...
adding a pattern for horizontal grids fixes the issue with vertical grids not laying out properly...
Still sounds like an underlying functionality issue to me but this may take care of the OP's issue.

Re: Curtain wall strange behaviour when adjusted for mullion size

VM_Jekabs — Wed, 02 Aug 2023 06:38:28 GMT

Looks like there just has to be at least 1 horizontal grid for it to work properly, doesn't matter if it's defined by the curtain wall type or manually placed. Very strange, but I'll have to accept @ToanDN answer for now. Thank you for your time everyone.