How much of the opening date is just waiting?
Put in each task with its duration and what must finish first and get back the opening date and which tasks set it. Ten tasks from lease to soft open, and three of them are pure waiting: a permit, a landlord approval and a floor screed curing. Twenty-seven of the ninety-one days on the critical path have nobody working on them.
Words on this sheet
- Predecessors: The tasks that have to finish before this one can start. Put their IDs here, separated by commas, and leave it blank when nothing has to come first.
- F statistic: The variation between the groups divided by the variation inside them.
Operations Starter Critical Path Pro engine
After you install, this is the model to open.
What Sets the Opening Date?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
This one runs on a Pro engine, and every free install includes five full-quality runs on your own numbers, shared across all five Pro engines rather than five for each. After that, Pro is $199/year.
The answer
- Opening day
- 91 working days from lease handover
- Waiting on the critical path
- 27 days permit plus screed cure: 30% of the date
- Critical tasks
- 9 of 10 only the landlord window can slip free
- The chased task
- 5 days of slack on landlord approval; not the driver
Ten tasks from lease handover to soft open, in working days. Three of them are not work at all. The landlord approval window, the council permit and the floor screed cure are queues and chemistry, and nobody on your team can go faster at any of them. Click Run and the store opens on day 91, driven by the lease, the design, the permit, the shopfit, the screed cure, the fixtures, the tills, the stock and the training.
The landlord approval carries 5 days of slack, so it is not on the critical path even though it feels like the thing everybody chases. Now add up the waiting on the critical path: 20 days for the permit plus 7 days for the cure is 27 days, which is 30% of the opening date. Nearly a third of this programme is time in which no cost is incurred, no crew is on site and the date moves anyway.
That is why adding fitters does not open the store earlier, and why the two useful conversations on this plan are with the council and with the screed supplier rather than with the contractor. The mechanical point worth learning is how the wait got onto the sheet at all. Critical Path reads finish-to-start dependencies and has nothing that expresses a lag between two tasks, so a wait has to be its own task, with its own duration and no owner.
That is not a workaround, it is the honest representation, because it puts the wait on the critical path where it belongs and lets the slack figures price it. Second run: submit the permit application on the outline drawings rather than the final set, so it stops waiting for the design. Clear the predecessor on the council permit and run again.
The opening moves from day 91 to day 86 and the permit picks up 11 days of slack, so it is off the critical path entirely. Five days, not twenty. The reason is the answer to the next question: the landlord approval takes over as the constraint the moment the permit stops being one. That is the shape of a plan with two queues running in parallel, and it is why removing the longest wait usually buys far less than its length.
Do it anyway, then go and negotiate the approval window, because it is now the thing setting the date. What this cannot tell you is whether the permit really takes twenty days at your council, and that number is worth a phone call rather than an assumption. To adapt it, put your own tasks in, give every wait its own task with a blank owner, and read the slack on anything with an owner before you agree to accelerate it.
The model
It arrives on a tab called Template: Store Opening, carrying these columns:
- ID
- Task
- Predecessors
- Duration (days)
- Owner
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
- Should you make more of your most profitable product?What Should We Make This Week?
- How few people can cover a seven-day week?How Few People Can Staff the Week?
- How many units does one delivery wait really need on the shelf?How many units to stock for 90% odds of no stockout?
- How many hires does a support week really need, in odds rather than averages?How many hires keep 85% odds of hitting the support target?
- Is a second shift enough for the peak week, or does it take a second line?What capacity gives 95% odds of covering peak demand?
- How much should you order when demand is uncertain?Inventory Order Quantity (Newsvendor)
Every model like this one, and the method behind them: Schedule risk analysis.