Out-of-Sequence CPM Schedules Require Outside the Box Solutions: My Top Ten Fav’s

Out-of-Sequence need not be the bane of the CPM scheduler’s existence

The jump from theory to practice in CPM scheduling is fraught with pitfalls that invariably trap all but those schedulers with a track-record of solid field experience and software usability or acumen. Yet even the best prepared schedules become deprecated as project scope veers out-of-sequence into a free for all for which there is no reliable model. This is always news to stakeholders and AE who don’t have the technical prowess to observe such nuances, and demand an accurate representation.

Projects have predictable sequence of operations, such as floor to floor, and through the trades: for example, the the representation of MEP sequences, beginning with sheet metal high and tight

from the underside of slab downward:

  • ductwork and duct insulation
  • steam fitting
  • plumbing and fire suppression
  • electrical

As floor to floor sequences deprecate, trades start to work where they have access. As trade sequences deprecate the order of installations can be upended upsetting coordination efforts. The scheduler notices the out-of-sequence, and tries to reflect the new project logic, but it’s a moving target that defies intuition and apt representation. In this way, the schedule begins its obsolescence stage. When the schedule becomes obsolete it goes without saying that it no longer serves any purpose. The bad news is that a buggered schedule precludes claim development, should there be one.

“never be a ‘consultant scheduler’ be a builder’s scheduler.

Savvy schedulers understand how schedule project logic deprecates as the job takes on a life of its own, and develop workarounds to keep project logic functional or tautologous. This practice involves thinking outside the traditional box of bland project controls that limit most practitioners’ abilities. Stakeholders and AE will find this thinking obscure and counterintuitive. But managing out-of-sequence schedules is where the best schedulers show their true mettle: the worst are over-reliant on third-party data.

But not so CMs and GCs, who are in the business of building no matter what the odds, and desire clarity for their timelines. Maintaining project logic is highly valued because the alternative is non-performance, and inability to stake a claim, as well as no vision in the forward pass. Their faces light up when you talk to them about revised project logic because they may be surprised at how much you know about building. They are surprised because their experience is that schedulers tend not to have a great wealth of building knowledge beyond the ‘book.’ This is profoundly more interesting to them than any spreadsheet or total float chart.

“- and guess what: builders and tradespeople love a scheduler who speaks their language as they often feel like they have no one to go to for scheduling issues.

Schedulers without field experience will be hard put to pivot when their timelines are out-of-sequence: they simply aren’t familiar or intimate enough with the comings and goings of real-time assemblies, other than what they read in a textbook.  That’s one of the reasons I insist that schedulers should have at least a few years in the field before they can think like a builder instead of data entry clerks.

Out-of-sequence program management is where supers, PMs, and CPM schedulers show their true mettle. Out-of-sequence management invariably levels the playing field between builder and technocrat, because books and software become merely a means to an ends: with an out-of-sequence program, you are no longer planning the project with the schedule, but planning the schedule around out-of-sequence program.

There’s a vast difference between the most highly possible detailed or resource and cost-loaded schedule and what happens in real time in a builder’s world: when you are running a building up out of the ground and you need to revise hoist and crane comeback sequences on the fly, there’s no time to recalculate resources and costs, or resequence to the minutest detail: you give the critical information as soon as you can, and fill in the logic and cost-loading later. Frankly, builder folks plum wouldn’t understand if you said you had to resequence and cost load a huge fragnet before you could turn around the schedule – you’d be out of a job.

“Busy site people don’t have the time to wait for tedious fragnets – much less cost and resource-loaded ones. They will build ‘on-top’ of your schedule, or without even referring to it.

Credit is due any scheduler wise enough to recognize that a schedule needs refined logic to represent out-of-sequence project logic. Sometimes this simply isn’t plausible, and it becomes necessary for a workaround. Following are my best practices of maintaining project logic integrity for fragmented sequences. These are just suggestions. You can always refer to the certification agencies for their position toward the ‘make-do’ conundrum that runs counter to their bland pedagogy. Or maybe your schedules always fall within the top 25th percentile of projects that make deadline:

  1. Study – the drawings, and think the work through like a project manager, or with a project manager. If you don’t know, or feel like you don’t really know, what you are doing, the builder folks will let you know: you are a book scheduler, not a builder’s In plain parlance, builders don’t particularly embrace or respect book schedulers, and frequently become frustrated in dealing with them.

In the real world, your certs will never determine your construction acumen – if you have none, they tend to obviate it. If you do have experience, they may enhance. Personally, I am always too busy to be concerned with them, and I have not seen demonstrable return of investment in their memberships.  If you want to be a construction scheduler, learn proper the way things are built, and then you can plan the work with your own intuition, as opposed to some standardized playbook. Such parametricized modeling will be achievable by AI within ten years, which means out-of-sequence work may be the only work a scheduler can get:

  1. Walk – the site and familiarize yourself with the revised project logic. This activity could be anywhere from an afternoon to an extended site assignment.
  2. Talk – to the foremen and construction personnel about the work – what sort of encumbrances they are experiencing and their concern for the future. Some will be prone to discuss previous delays and conditions, but this sort of discourse will not be productive unless you are trying to memorialize past delays.
  3. Unlink – the predecessors of the out-of-sequence activities to resolve errors, and –
  4. Unlink – the successors of the out-of-sequence activities to resolve errors. As completed activities are de-linked, they become open-ended – but that’s OK, because their conclusion is imminent, i.e., they have already started: no one cares about out-of-sequence in the backward pass.
  5. Modifyfinish-to-finish relationships to start-to-start, between out-of-sequence predecessors that have not been completed, and their successors. Note, if you only change the predecessor relationships to start-to-start, the successor will be out-of-sequence when it is concluded if the predecessor has not concluded.
  6. Delete – merge, or dissolve problematic out-of-sequence activities that are no longer germane to the project logic. That’s right: I said ‘we’re shedding dead weight and useless bits of information before they pollute the atmosphere.’
  7. Clean – the messy bits of obsolete lag and constraints left by the out-of-sequence storm as these tend to clutter the project logic and skew modeling. If you happen to use Acumen Fuse, than you might know that its Cleanser module does almost all of your housekeeping for you.
  8. Focus – on critical path, milestones and the most intuitive and natural path of the remaining project logic.
  9. Validate – your project logic with an analysis tool, such as Acumen Fuse: your timeline has changed considerably, delinked, and otherwise fragmented. Schedules with a few thousand activities will be otherwise resistant to analysis after restructuring if you don’t perform this important step.

Fastidious housekeeping will keep your schedule lean and mean all the way to close out, and serves to obviate rebaselining efforts. Working backward from the longest path, you can better hone in and drill down from an order of magnitude, as opposed to a disorder of random changes, the remaining critical path project logic. The proceeds of this effort I call a ‘completion schedule’: as any out of sequence schedule sorely yearns for. On this point, CMs, GCs, and AE and stakeholders will agree, that it provides the most important piece of information they need – a calculated completion date.

Written by

Derek Graham is a Primavera 6 scheduler and schedule oversight consultant for public and private sector projects with four decades of construction industry experience. He has been an active construction expert witness in over 30 cases - both nationwide, and Federally, since 2006, when his book Managing Residential Construction Projects, was published by McGraw Hill