While commenting on a post at BIM MANAGER, I started to think about how we reconcile discrepancies in project information. Traditionally the drawings have taken precedent. But which drawing? The design intent drawing or the shop drawing? Plumbing waste plan or the waste isometric? Heck, even plan, section and elevation are known to have information that’s not coordinated in traditionally drafted drawing sets (even in sets produced from a model, but that’s poor use of the tool.) Add to this the additional layers of complexity of Specifications, Cut Sheets, Hardware and Equipment Schedules, etc and you have ample opportunity for discrepancies. Cue RFI. Cue Change Order.
Enter the BIM. Your one stop depository of information about the project. Today, right now, we all have at our disposal the tools necessary to link ALL project information to a BIM. Read that last again. Think about it, Design Intent, Specifications, Construction Sequencing, Client Meeting results (Approvals and Markups,) Fabrication Drawings, As-Builts, O&M manuals, Asset management, Building Controls, etc. etc. ALL IN ONE PLACE.
All of this information can either be derived from the model or linked to it. So there should be NO MORE DISCREPANCIES. Bold statement for sure. But hear me out. If your spec is linked to what’s in the model, it can only reflect the information you need based on design intent. If your drawing sets are extracted from the model, it must reflect what is there.
Discrepancies enter the picture when the deliverable doesn’t reflect the current state of the model. The spec is compiled by hand, the model changes (programs that extract specs from BIM often update “instantly.”) Static, stock details that represent “typical” conditions (they are never typical.) Text that calls out door sizes (practically every BIM authoring solution allows “tagging” of smart objects, so the text changes when the object changes.)
So, given that discrepancies will creep into our project (through poor use of our tools, scheduling pressures, lack of technology, etc) how should we rectify and reconcile them? I attest that the MODEL should have the final word. Why? If the model is constructed from objects that are dimensionally accurate and data rich, you have the actual building (just before it exists in reality) to guide your decision making.
When a condition isn’t clear in the “printed” documents, go look at it in the model. View it from infinite angles, I guarantee you will have a more clear understanding of the condition than you can receive from ANY number of 2D drawings.
If information is missing from the plan set (and the model) MODEL IT!! Take the time to model the condition. What wouldn’t we give to have the budget for unlimited mock-ups. Well, we don’t have unlimited budget (I don’t anyway) but Virtual Mock-ups offer extreme value. Model any conditions that aren’t clear. Communicate with images or even videos of those conditions. Get the model in the hands of the decision makers. The closer you can get the model to those asking the questions, the better.
Model correctly and use those models to reconcile any discrepancies.
Don’t let discrepancies in your project information make you afraid of the Big Bad BIM.