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BimBlog: Less is More... more or less

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    BimBlog: Less is More... more or less

    When we ask users how they model and define their Revit assemblies(walls, floors, roofs) most will tell us that their libraries are made up ofcomplete assemblies created from inside to outside.
    As we move away from traditional ‘model to get the drawings’workflows and begin to create models that are shared and leveraged beyond ourown needs as architects, we start to realize that our initial approaches mightneed to be re-examined. For the purposes of this exercise we’ll use walls butthe same principles apply to any assembly.

    Thinking of a wall as a complete assembly from inside tooutside seems like the logical choice but when you consider all factors a realcase can be made for breaking things down a bit. It may seem counter intuitiveto suggest modeling more individual walls to achieve greater flexibility butthe numbers bear this out. We’ll get back to the numbers in a moment.

    Look at the image below and, although a little extreme, itillustrates the difficulty when we consider how many variables affect anassembly as it moves through a building.

    The core structure of a wall may have many variations ofinterior finish or exterior cladding. An exterior structural concrete wallmight have a variety of cladding materials or systems applied to the face ofthe concrete. At the same time a number of interior conditions are encounteredalong that wall as it moves from room to room in the interior. Variouscombinations of furring, strapping, both insulated and non-insulated, plumbingchases, various code and structural needs come together to create a mindboggling number of variations. This doesn’t even take into account the ‘Z’factor of various finishes not going the full height of a wall.

    If we look at it in terms of a matrix that shows a series ofcores and a variety of cladding/finish conditions we begin to see just how many‘complete’ assembly types would need to be created to accommodate allconditions. The list of assembly types would be vast and users would probablyfind it difficult to locate the correct assembly for placement in the project andmanaging this library becomes cumbersome. In addition, every time a newcladding/finish material is introduced; it raises the possibility that multiplenew whole assemblies will be needed.

    Concrete walls at the structural core of a residential tower
    Interior Finish/Cladding
    Exterior Finish/Cladding
    A Furring and gypsum board 1 Concrete 200 mm thick A Furring and gypsum board
    B Plumbing chase with ceramic tile 2 Concrete 250 mm thick B No Finish
    C Wood Panel over furring (Lobby) 3 Concrete 300 mm thick C Insulated furring and gypsum board
    Possible combinations when created as complete assemblies – A1A, A1B, A1C, A2A, A2B etc. 27 unique wall types
    Number of separate core/finish/cladding assemblies to create those same 27 unique conditions – 9 unique wall types

    In the breakdown scenario if a new finish is required onlythe finish assembly needs to be added to the library. It can then be ‘applied’to any number of core assemblies with any number of finishes on the other side.

    Simplifying the management of all these assemblies has addedbenefits when we look at the accuracy of our model and a truly collaborativeBIM workflow. The structural consultant is generally not too concerned aboutthe finishes on the interior face of a concrete wall but at some point they willbe in control the structural portion of the wall. If the architect places thecore concrete wall at the design development stage the structural consultantneeds only to replace the architectural wall with his structural wall whenlinking the architect’s model. The same thinking would apply if interiors are aseparate package from the shell building. Interior ‘finish’ assemblies can beplaced on a separate workset, or in the case of multiple models, in a separateID model with architecture linked in as a .

    From a design standpoint placeholder walls can be modeledwell before design decisions are finalized. With careful consideration forlocation lines of placed assemblies, accommodating design variations andreacting to design changes can be propagated more quickly and more predictably.

    The contractor and sub trades can more easily schedule workby trades or discipline, assign task ID information for construction schedulingand, if desired, supplement the model with fabrication level detail.

    At first glance when it is suggested that the user needs toplace more walls or break down floor and roof assemblies into separatecomponent parts there can be resistance. “If I need to place more walls, that’smore work for me!” It may appear that way on the surface but the numbers don’tlie.
    Sometimes more is less!

    Click here to view the entire blog post.

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