Background:
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.
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.
Pricing:
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.
Modeling:
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:
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.
Building:
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.
Conclusion:
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.