Additive vs Deductive Project Management

How we are tracking progress has everything to do with our ability to manage uncertainty.

The purpose of this article is to introduce concepts of additive and deductive manufacturing as models for approaching project management strategies in the construction industry.  While additive manufacturing, a branch of which is known as 3-D printing, is quickly making its way into the construction industry; this article is going to look at the differences between additive and deductive in terms of their systemic inferences rather than their technical differences.  By the end of this comparison, you should understand the concepts "Decision Date" and "Additive Project Management", and well as understand the values of each.

Deductive manufacturing is the process of beginning with a solid piece of raw material, then slowly removing strategic amounts from strategic locations until a member, tool, part, or product is produced.

On the other hand, additive manufacturing is the process of transferring a digital model into a robotic mechanism, from which an object is extruded by way of leveraging the dynamics of particularly malleable materials.

For the purpose of this article, however, we point out that additive methods are ground-up, whereas deductive methods are top-down.  When transferring these manufacturing concepts  into the realm of project management two (2) distinct systems of approach come to light:
  1. Top-Down construction management begins with one large raw material (the estimate), and through time deduct units of measure (based on reports).  The result is intended to be a report regarding how that project is performing.  That is to say, deductive project management begins with a budget.  The large budget is broken in to smaller budgets from which they are reduced by the amount of productivity that is reported to have transpired over a given time.  From this data, management teams deduce average productivity rates and the amount of work remaining to be completed.  This calculation allows them, by assuming the average productivity rate, to come to a conclusion regarding the amount of time and expense that will be required to complete the project.
  2. Bottom-Up construction management begins by grouping the project into its material needs, including:  pipe/valves/fittings, manufactured/motored system equipment, the tools necessary for installation, etc.  These groups typically correlate to a geographical portion of the construction project.  From that point the groups are associated with the project's schedule and the materials are associated with the system and sub-system they will comprise relative to the final product or project.  This material mapping allows project managers to build a projection of the project's financial utility as well as its operational demands.  It is with this projection that a project manager, by way of procuring sample data from the construction project, can come to a conclusion regarding the amount of time and expense that will be required to complete the project.

One of the great advantages of Additive Project Management (APM) is the ability to frame a discussion with the client regarding the topic of needing their input in order to move the project forward.  APM allows a contractor to calculate what we call the "Decision Date", as follows:

For example, suppose we expect to need a particular kit of material on site for installation on project day 100.  Then Df=100 (100 days after beginning the project).  Further suppose that the vendor will receive the material 14 days after we order it (Tl=14), we need 5 days to QC the material (Tqc=5), and we need one day to deliver the material to the job site after completing QC (M=1).  Our variables are then:
Df=  100
P=(14)2+5=  33
Tl=   14
Tqc= 5
M=  1

And so N=Df-P-M=100-33-1=66.

Day 66 into the project is the last day we can order the material needed for this particular kit.  If we wait longer than day 66, the material will not have time to be delivered and work through the QC process.

By managing from the perspective of the constraint, (the installation of the materials and equipment at the construction site, and subsequently the flow of materials and equipment to that construction site), we're able to educate the client in an intuitive way on the importance of answering critical questions in a timely manner.

A fair stream of critical logic, however, could also be; "Why would I want to risk cutting it that close with my material deliveries?  Wouldn't it be more effective to elevate the constraint by ordering all of the materials up front?  Doesn't that ensure that the project never stops?"  This is an intuition that drives most of the material management systems in construction today.  It becomes especially alluring when supported by the notion of economies-of-scale.  There are several costly misconceptions with this approach, however.  Many of which stem from the top-down, deductive approach to management styles.

Applying the concept of a Monte Carlo simulator to a construction project can be a helpful way of thinking about these misconceptions.

Below is a visual representation of a Monte Carlo simulation.  In general, a Monte Carlo simulation is intended to represent a simulation of the dynamics of a collection of variables in an attempt to articulate the probability of a given outcome or set of outcomes.

The left of the graph is the moment that the variables in question came together to create the potential outcomes.  As time progresses, the potential outcomes progress along the X-axis from left to right.  In the image above, the area on the right side of the graph with the darkest coloring represents the most probable outcome.  Now let's frame a Construction project in this thought model.  We start with a scope of work, that being the very left side of this graph.  As we progress along the X-axis, RFI are introduced, change orders are requested, subcontractors fall behind or go out of business all-together.  In essence, we are unable to predict where, on the Y-axis, this project will end up.  

Additive Project Management addresses this uncertainty by flipping this simulation process into a model of visualizing the known-unknowns.

Additive Project Management embraces the fact that there are known-unknowns, as well as unknown-unknowns.  In fact, there are dozens, if not hundreds or even thousands of them.  Flipping the model in this way (keeping time along the X-axis and the probability of outcomes along the Y-axis) demonstrates the value of waiting as long as possible to release materials.  The project is given an amount of time to demonstrate its unknown variables, to show us how it will end.  This information allows a project manager to make a more informed management decision.

In addition to this dynamic, an advantage of Additive Project Management is in the resulting deliveries containing smaller quantities.  Smaller quantities are easier to measure for accuracy and are safer to move around a construction project.  Knowing what material is projected to arrive, knowing when it will arrive, and knowing to which batch it is to be grouped allows for us to be on the correct side of the "real-time" limit.

"Real Time" is a slogan that refers the the size of a feedback loop relative to the amount of time necessary to return data.  Without delving into the philosophical mosaic of the meaning of "now", we can all agree that we would rather be proactive than reactive.  Therefore, in working from a state of projection, and by way of using the projects materials and tools as the unit of measurement, we can inspect all phases of the project's supply chain simultaneously at a given time with equal amounts of information and therefore equal amounts of effectiveness.

Whereas, with deductive managerial methods, the application of "real time" feedback loops can demonstrate only the data indicated from the construction site and compare them only to the schedule or budget.