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Thread: any RULES for LOD tolerances

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    Member uaifestival's Avatar
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    Question any RULES for LOD tolerances

    Hello there,
    is Anybody using a scale for clash tolerances as LOD are going toward Construction phase?

    Say something like this
    LOD 100 (Concept phase) 100mm
    LOD 200 (50mm)
    LOD 300 (25mm)
    LOD 400 1mm

    and there is any document published by AIA about it?

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    Forum Addict GMcDowellJr's Avatar
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    None that Ive seen. Considering LOD 300 is supposed to be accurate in terms of size and location, a 25mm/1 margin seems excessive.

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    Member Knitro87's Avatar
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    USIBD published a Level Of Accuracy (LOA) specification back in 2014, but I don't think it ever took off. This document was supposed to be used concurrently with an LOD specification.

    https://www.spar3d.com/blogs/measure...pecificiation/

    Accuracy is harder to define during design because so much is dependent on site conditions, construction tolerances, and skilled labor availability.

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    Administrator Twiceroadsfool's Avatar
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    Quote Originally Posted by uaifestival View Post
    Hello there,
    is Anybody using a scale for clash tolerances as LOD are going toward Construction phase?

    Say something like this
    LOD 100 (Concept phase) 100mm
    LOD 200 (50mm)
    LOD 300 (25mm)
    LOD 400 1mm

    and there is any document published by AIA about it?
    I honestly dont know why anyone would use different "tolerances" at different phases of a project, regardless: The project is either at a stage where you can rely on it dimensionally (ready for real element by element coordination) or it isnt (ready for visual inspection only).

    If its in the latter, i wouldnt be wasting time running "3d coordination" element by element.

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    Member uaifestival's Avatar
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    Thanks all for a quick reply.
    Tolerances matters in our case as the model is to be pass to another firm after LOD200. A local one that would develop to LOD300 to adapt local rules and customs. The client also has its own perspective and they clash at 1mm at LOD100 which is absurd, but Autodesk is selling the software in each country with their own freedom. Basically the client has a limited knowledge (of course He likes to push buttons here and there) and I would like to ground down our request on shareable best practices. So if you have any clue about documents on that respect, that would be awesome.

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    Administrator Twiceroadsfool's Avatar
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    Quote Originally Posted by uaifestival View Post
    Thanks all for a quick reply.
    Tolerances matters in our case as the model is to be pass to another firm after LOD200. A local one that would develop to LOD300 to adapt local rules and customs. The client also has its own perspective and they clash at 1mm at LOD100 which is absurd, but Autodesk is selling the software in each country with their own freedom. Basically the client has a limited knowledge (of course He likes to push buttons here and there) and I would like to ground down our request on shareable best practices. So if you have any clue about documents on that respect, that would be awesome.
    I would counter that in this situation tolerance STILL doesnt matter. Setting up a "tolerance value" isnt going to suddenly make it value adding that they are doing item by item clash detection at LOD 200. Its still somewhat of a pointless exercise and waste of money, IMHO. Setting a value on it isnt going to make it more valuable, or less of a waste.

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    Member uaifestival's Avatar
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    Dear Twiceroadsfool, you are absolutely right that is a waste of money/time, and the reason of the post primarily. How to make the client to reach an agreement on that, because that waste is our time to fix things they should not be fixed at this stage.
    So doing a clash (mainly between arch and STR, as mep is not there at this point) with 1 mm, shows up 20 clashes, make it at 5mmm or 10mm reduce the clashes so our time/waste. I would call it "mitigation" of the problem when a Client is unreasonable. Still I have to make up a motivation.
    Last edited by uaifestival; July 29th, 2020 at 12:05 AM.

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    Administrator Twiceroadsfool's Avatar
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    Quote Originally Posted by uaifestival View Post
    Dear Twiceroadsfool, you are absolutely right that is a waste of money/time, and the reason of the post primarily. How to make the client to reach an agreement on that, because that waste is our time to fix things they should not be fixed at this stage.
    So doing a clash (mainly between arch and STR, as mep is not there at this point) with 1 mm, shows up 20 clashes, make it at 5mmm or 10mm reduce the clashes so our time/waste. I would call it "mitigation" of the problem when a Client is unreasonable. Still I have to make up a motivation.
    Yeah. I get it, believe me.

    IMVHO the idea of "clashing" arch against struct is nuts, anyway. I mean, the majority of walls are going to class with framing members overhead.

    Those things aren't clashes. Why are they doing that test at all?

    I would push for visual walk through or visual inspection. In my opinion, ACTUAL clashing is pointless until all disciplines are there in fab form. It literally has to all be started over at that point anyway. Waste of money.

    Sent from my Pixel 3 XL using Tapatalk

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    Quote Originally Posted by uaifestival View Post
    Hello there,
    is Anybody using a scale for clash tolerances as LOD are going toward Construction phase?

    Say something like this
    LOD 100 (Concept phase) 100mm
    LOD 200 (50mm)
    LOD 300 (25mm)
    LOD 400 1mm

    and there is any document published by AIA about it?
    I dont think there ever could be, a lot is down to building tolerances and each contractor and sub-contractor seems to want a different tolerance compared to another. What has worked on our current project wouldnt have worked on the one before etc.
    Clash detection is a minefield and one that far too many people rely upon as a silver bullet to solve all issues and it never does.
    However we have found running specific smaller tests ie 10th floor M&E vs SE with a specific dimensional tolerance set is a way where we have managed to isolate specific clashes better rather than running a whole building clash test with one clash set.

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