January 25, 2015 by David Moore
I sat down last week with an engineer who has worked in the industry even longer than I have. We discussed the current state of design technology and its implementation. Our industry is in flux, on the precipice of possibilities. BIM offers us tools to increase productivity and efficiency in design and management as well as implementation, construction, and maintenance. But roles and responsibilities are changing.
In an earlier post I talked about what we, as contractors, expect from architects and engineers when we're given a project for pricing and what we more often get. My most recent project consisted of a set of architectural drawings, from which I needed to provide a take-off for estimating a budget price. To do this required designing the plumbing system from concept drawings that hadn't been sent to an engineer yet.
At this point in the bumpy ride toward BIM technology everyone is feeling their way in the dark and the lines between design and build are blurred like never before. Who does what, when? That question is being answered in as many ways as there are projects. The next design I look at may be a complete Revit model or a sketch on paper. Uncertainty isn't good for production or the bottom line.
Most of my conversation with the engineer concerned that very question. How far does he take his design and when does he hand it off to me. We are all looking for efficient workflows with minimal reworking. In the past engineers developed a design in AutoCAD, or by hand, and handed off a set of blueprints to the builder. So where does BIM, 3D modeling, and coordination fall in?
My friend the engineer provided great insight into decades of design work and I threw in my decades of work in the field implementing those designs. Together we found some basic parameters for adding BIM to the process and, I think, an efficient workflow that minimizes overlap. Every project is unique, and different engineers and contractors have varying capabilities and needs. But there are commonalities enough for standardization.
For the sake of simplicity the basic process of taking a project from concept to finish product can be broken down into five basic steps: Design, Price, Model, Coordinate, and Build. Of course these areas overlap and inform each other, but they are separate enough for our purposes. I will show those areas of overlap as we go and what one area needs to take from another. Let's start with Design.
The design process takes an owner's vision from initial concept through a workable design. The basic structure is defined along with layout of main MEP systems and equipment. Contractors can use this to generate material take-offs and estimate labor and material costs. This design does not need to be completely detailed and ready for construction.
One of the points the engineer made concerned AutoCAD versus Revit in basic design. Revit models building information. It is a true BIM modeling tool, but plugging in all that data is time consuming. During the design phase information is changing and dynamic, and we've established our basic design doesn't need that level of detail.
It is much more efficient, in the early stages of design, to simple draw the structure and MEP systems in AutoCAD. What builders need for their cost estimates is, as I said before, basic lay-outs and equipment schedules. If the A/E spend time creating a detailed model in Revit, much of that work will require changing later on in other phases; as we shall see.
During the pricing phase builders and contractors take the drawings or basic model the A/E provides and generate cost estimates. Often contractors see ways that cost can be reduced and/or time saved by slight changes to the design. Alternates can be requested or offered and the most economic design can move on to the next phase.
This is where a detailed model becomes cumbersome as the design changes slightly, but the model requires a lot of time to edit all of the pertinent data. This is not to say we couldn't or shouldn't start from the beginning in Revit. A basic model can be produced in Revit without the tons of data in a detailed BIM model; that can all be added later. But an AutoCAD drawing is sufficient at this stage and can be imported in Revit when the full BIM model is developed. Which is the next phase.
Once prices, materials, and schedules are hammered out, and the design documents reflect any changes made, it's time to build a more detailed model. This may be performed by the A/E, or by individual contractors with the A/E's oversight and approval. In the industry we refer to that as design assist. This phase goes hand-and-glove with the traditional process of contractors submitting data on materials and equipment they plan to use on the project to the A/E.
There will be further changes to the model, but during this phase a BIM model takes shape as actual material and equipment data is entered. If the basic design was in Revit we fill in, or edit, real-world data where needed. If AutoCAD was used we import the .DWG files and begin modeling using them as our guide. Again, routing and equipment placement are subject to change, so we keep it basic, but material types and equipment are set so we apply all those details.
This phase provides us with a solid working model to take into coordination.
Coordination is the heart of BIM. During this phase we take the building model and the various MEP models and work out any conflicts that emerge. Our models must be sufficiently detailed to make those conflicts apparent, yet fluid enough for changes to resolve those clashes. Equipment may be moved or piping rerouted, but the core data of material types and equipment types doesn't change.
Detailing the model continues throughout this phase. By the end of coordination the model should be a true representation of what the construction personnel will install on site. Details, spool drawings, and elevations can be produced as needed through the building phase. Points can be established for layout, and material list generated for purchasing.
During the building phase the model is used for construction. Very few changes are made unless previously unknown field conditions require a change, or the owner requests a change. These changes are made as needed, in a timely manner, to keep the model up-to-date throughout construction. Additional data can also be added to the model during this time to meet owner requirements at close-out; operation and maintenance data, warranties, valve charts, etc.
At the end of construction the model, if kept up to date, should reflect the actual conditions and contain any additional information requested by the owner in the contract. The BIM model has become your As-Built model and contains all of your close-out documentation in one Revit file.
In the real world the outlines of these basic steps will inevitably blur and shift as various stakeholders shoulder sundry responsibilities in designing and building different projects. There will be overlap, wasted work, and conflicts, but the field is clearing and in a few years standards will emerge and best practices will evolve. For now we need to continue looking for the most efficient ways to get the job done.
All of these steps need to happen on any project implementing BIM design and coordination for an efficient workflow. Who does what when must be considered, and possibly negotiated, but the work needs to get done. BIM can and does provide us with the tools for greater efficiency and therefore higher profits if we use it intelligently.
If you have thoughts, questions, or ideas on the best ways to implement Building Information Technology in your business model send me an EMAIL or leave a comment below.
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