How Much to Model? – Part 1

by Rob Oberle

The transition to BIM by an architectural firm goes beyond learning how to model, use new software or set up office standards. It requires all of this as well as support from the top down of the transition by the firm principals, management, on down. It is important for the PM’s to understand the limitations of the software and what is reasonable to model to achieve the documentation goals and deadline.

One of the biggest problems that is under debate in firms making this transition is “How much to model?”. For Schematic Design, Entitlement Documents and Design Development this is not as difficult because the model is used mainly for form, which allows the model to be less detailed from a constructability standpoint.

It is in Construction Documents that firms struggle with “How much to model?”. Is that piece of flashing at the top of the wall important to model? How important are the reveals to model? Do the wall composites need to be accurate with each element (i.e. finish, sheathing, core) or is it just having the overall thickness of the wall enough? This type of questioning could go on forever, so instead I would say the more important question to ask is “Will the element I am about to model interact with other elements in a way that requires me to model this with specific detail?”


Categories: BIM | 1 comment

One Comment

  1. Similar to the MPS process (Model Progression Specification) the idea is to approach the design intent from general geometric definitions to specific material, sizes finishes, and construction methods with the Model.

    Keeping this in mind, I would split this question depending on the purpose of the model:

    How much to model? -For little BIM- Automatic Documentation.
    On the schematic design, you can keep playing with “generic” walls, openings, slabs, showing only nominal sizes and very few technical details. There the architects will use more the rendering capabilities of the model than anything else.

    Once we have reached the Construction Documents stage, the more accurate detailed the model gets, more accurate will be the printed drawings, and less drafting effort requires for Documentation.
    There you will find very useful “smart” capabilities of the software to show wall composites, Standard steel size elements, standard doors, etc…
    As a general Rule you can settle not to Model anything smaller than 4 cubic inches or 100 cubic mm. this means Not to model anything that can fit in an imaginary 4″x4″x4″box. The only exception to this rule is if what you are modeling is a part of a bigger element, like a handle.

    A very complex will automatize the documentation process, but it requires more modeling maintenance and stronger hardware.

    How much to model? -For Big BIM- IFC interchange, 4D and 5D coordination, quantity-energy-and Building Maintenance analysis.

    Once you start the process -from the very beginning- you have to set all the IFC information required from all the parts. At this point would be useful to use IPD, and agree on this earlier.
    Here you are more focused on the Information contained in every element of the model than just the geometrical data contained on it.
    You will be more careful on the Integrity of the model and you will have to add non-construction elements, like Zones or Room tags, just to fill the empty spaces between the walls and slabs.
    This probably wouldn’t be much more to model, but to model carefully to keep IFC compatibility.

    On my opinion, very complex models helps in Collaboration, because the team can communicate trough the model, without needing to say much more. You can say that “everything” is on the model: the core material, the finishes, the colors… the prices… the carbon footprint…
    And in the long term it would be useful for the entire life of the building.
    I support for complex Models, but those are only useful if the consultants are using it, if the final user is going to use it.
    Otherwise, then just use it to Automatize your documentation process.

    Regards
    Nando Mogollon
    Architect.

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