Calculating construction schedules backward is a pain. It all started with that 'grumble'

“Tasuke-kun, do you have a moment?”

One evening, as I was organizing documents at my desk, my colleague A approached me with a slightly tired look on their face.
They were holding a laptop in their hand.

Tasuke-kun
“What’s wrong, A-san?
You look like your soul is about to leave your body.”

Colleague A
“Well, the sales rep just asked me, ‘I’m going to a meeting with a client, and they asked for a rough schedule—about when do you think it will be finished?’”

Tasuke-kun
“Ah, that classic ‘rough construction schedule check.’”

Colleague A
“Exactly! That’s the one!
They don’t need a detailed schedule until after the contract is signed; they just want to know the general flow of ‘about what month will it be finished?’
But still...”

A-san let out a deep sigh and grumbled like this.

“Calculating that construction schedule backward is always a low-key pain.”

The moment I heard those words, I nodded so hard I thought my head might fall off.

It’s true. That really is low-key exhausting.

It’s not an official schedule. That’s exactly why it’s so troublesome.

When you’re managing construction or renovation sites, you encounter this question about a ‘rough estimate’ time and time again.

“If we start around this day, when do you think it will finish?”
“About what month will it take until?”

The clients and sales reps asking don’t have any bad intentions at all.
In fact, it’s a perfectly natural question for them to ask so they can plan ahead.

They don’t want a precise, official schedule.
They just want to align their expectations with ours by saying, ‘It will probably go something like this.’

And yet, when we try to think about it, our brains go into overdrive.

• “The total construction period is probably about 130 days.”

• “If construction starts on this day, we need to allow a few days for preparation...”

• “Assuming foundation work takes about 2 to 3 weeks, does it end around here?”

• "From there, the carpentry work comes in, and we'll proceed with the roof and exterior in parallel..."

The task of lining up and assembling the process entirely in your head while glaring at a calendar.
If you hit a holiday or a long weekend in the middle, the mental abacus you worked so hard to assemble comes crashing down with a, "Wait? How many days off is this?"

In the end, you're forced to scribble on a scrap of paper, "Let's see, the foundation takes X days, the carpenters take Y days..." while frantically tapping away at a calculator.

The stress of having to think it through manually from scratch every time

I think the most annoying part of this "rough reverse calculation of the construction period" is that "you are manually reassembling it from scratch every single time."

If the start date shifts by just one week, you have to re-examine every single process date on the calendar.
If the total construction period changes from "120 days" to "130 days," you have to start tapping the calculator all over again.

It might only take a few minutes, or maybe ten minutes or so, in terms of effort.
But during that time, your brain's memory is running at full capacity.

It's also scary because if you just say it verbally thinking, "I'm just telling the sales rep for now," it can lead to small discrepancies later, like them saying, "That's not the date you told me back then."

A blank Excel sheet was open on Person A's laptop screen.
It seems they were trying to manually fill in the cells with blue one by one, just to create a graph of the rough flow.

Tasuke-kun
"Person A, that 'filling it in by hand while looking at a calendar' thing, I used to do that too..."
It makes you want to scream when the dates change halfway through, doesn't it?"

Colleague A
"Exactly! Just a slight change in the start date, and you have to shift everything back and repaint it, right?"
Just thinking about it makes my brain freeze."

What lies behind the "annoyance"

After seeing Person A off, I went back to my seat and thought.

The reason calculating construction schedules in reverse is a pain isn't because we lack ability or are being lazy.
The "structure of manually recalculating 'fluid schedules that change repeatedly' every time"must be the primary cause of our mental fatigue.

I don't want to use any more of my precious mental energy just for a "rough check" before the stage of creating a precise project schedule.

"Isn't there some way to make it so that just by entering the start date and the total construction period, the flow is automatically visualized in a flash...?"

From that day on, I decided to start building a system to make the "annoyance of reverse construction scheduling" a little easier.

If you, too, find yourself agonizing over a calendar, saying "Let's see..." before meetings or in response to sudden questions from sales reps, please try deciding this from tomorrow.

When asked for an estimated construction schedule, don't try to calculate it only in your head; just start by writing down the total construction period and the process on paper.

You can leave the number crunching to the system.
Why not start by freeing up some mental memory first?

Starting tomorrow, I would like to dissect a bit more deeply why this 'rough calculation' confuses us so much every single time.