Workshop Capacity: Same Bay Count, a Fraction of the Work
8m 34s
A maintenance workshop’s required bay count can be accurately determined through either a zero-base buildup or a top-down approach, with both methods arriving at the same result when done correctly. The zero-base method sums up all scheduled maintenance tasks across assets, but it depends on assumptions about work frequency and strategy, and fails to account for non-maintenance space needs like staging or equipment access. This can lead to inflated or underestimated demand if assumptions are subtly adjusted to meet pressures. In contrast, the top-down method begins with real fleet downtime data—actual maintenance outages—as a factual baseline, then assigns known activities to specific locations, with unmeasured or unrecorded work placed into a visible residual category. This residual is key, as it captures unmeasured demand without inflating bay counts. The top-down approach is more transparent, with assumptions clearly defined and open to review, reducing the risk of hidden manipulation. For expanding fleets, this method is recommended: it’s simpler, more realistic, and ensures that both current demand and future growth are understood through clear, collaborative site-based definitions. The takeaway is that accuracy and transparency matter more than complexity—simple, evidence-based methods deliver better outcomes.
(upbeat music)
- G'day, and welcome back to Maintenance Break.
Bite-sized insights, one break at a time.
I'm Pete.
- And I'm Drew.
Pete, I want to start with a report you actually wrote.
Real fleet, real question.
How many workshop bays does the site actually need?
And here's the twist.
You ran it two completely different ways
and landed on the same bay count both times.
- Yeah, that one stuck with me.
Same fleet, same answer,
but one method took me weeks more work.
That's the thing that report taught me.
Getting to the right number was never the hard part.
Getting to it fast without fudging anything along the way,
that's the actual skill.
- Two ways to calculate workshop bay requirements,
both landing in the same place.
Two different methods, same destination,
if you do them properly.
One's a zero base buildup.
The other is what we typically use and it's top down.
- All right, walk me through the zero base one first.
What does build it from zero actually mean?
- You take every single asset on site,
pull its full maintenance strategy,
every tire change, every wash, every service,
and multiply the frequency by the duration.
Then you add the whole lot up.
Say a haul truck needs a 500 hour service
that takes four hours and it runs 6000 hours a year.
That's 12 services, 48 hours for that one truck.
You assign it to a maintenance location
and do that for every asset.
From there, it's just maths.
- Sounds thorough.
- It is and done properly, it gets you to the right number.
But it's only as good as the maintenance strategy
sitting underneath it and how will you line up
the component next Jews and the assumptions you make
for the corrective and breakdown work.
- You can never actually get away from making assumptions.
- No, but here's the trap that catches people out.
You're continually adding maintenance time.
Task by task, outage by outage.
And if you never stop to check that running total
against what the fleet's actual availability is telling you,
you can end up a long way off.
Could be well short, could be well over.
You wouldn't know either way.
- Short, I thought the worry was always
the number creeping up too high.
- That's usually where the creep starts, funnily enough.
The honest buildup comes in well short
of what the fleet's really costing you in bay demand.
Because the scheduled maintenance list is not the full picture.
And instead of going back and asking why it's short,
people start padding assumptions to close the gap.
- What's it missing that a scheduled list just can't catch?
- You've still got your corrective work
and your breakdown sitting completely outside any task list.
So you've got to layer assumptions on top
just to ensure workshop demand is captured.
- Right, is there anything else?
- Bay sterilization for one.
Take a major component change.
Where Bayes are too small,
it's not uncommon to use the bay beside
as a staging area for components.
Other causes to sterilize the bay beside
are keeping free for a tire handler or mobile crane access.
Neither of those are extra maintenance time.
It's the same task.
It just uses more than one bay than the task duration
on its own would suggest.
- So the Bayes blocked for reasons
that have got nothing to do with how long the maintenance takes.
- Exactly, none of that shows up
on a maintenance strategy document.
Because it's not a task, it's a footprint requirement.
Zero base counts the work.
It doesn't count what the work actually needs around it
and is often overlooked in zero base capacity buildups.
- And how honest are those assumptions usually turn out to be?
- Depends who's under pressure to justify a bigger workshop.
I've seen it happen more than once.
Those assumptions get quietly nudged upward,
one line at a time,
until the final workshop demand across the whole fleet
is bigger than the underlying work actually supports.
It still looks rigorous.
Every number's got a source.
It's just that a few of those sources were fudged
to get the answer someone wanted.
That's the real risk.
Not that zero base is wrong in theory.
- So done properly, it gets you there.
Talk me through the top down version and why we use it.
- Top down starts from the other end entirely.
You don't ask what should the fleet need?
Availability already gives you the answer
to how much maintenance downtime did this fleet actually have.
That number's not an assumption.
It's a fact the fleet already handed you.
Your whole job after that is just working out where it went.
- So you're not building the number,
you're just allocating it.
- That's exactly it.
You place every maintenance event you can identify,
your washes, your tire changes, your PMs, your shutdowns
against whichever maintenance location
it actually happens in.
Then whatever's left over, the harder to calculate stuff
goes into one nominated bucket.
We call it the residual.
And it's usually somewhere like field repair
or the general maintenance bay,
wherever genuinely makes sense for that leftover work
to land on a particular fleet.
- And that residual is doing some heavy lifting.
It's the single most consequential decision
in the entire model drew.
Nominate a workshop bay as your residual
and every hour you never measured
gets counted straight into your bay demand.
Nominate somewhere like field,
work that genuinely happens out in the pit,
unlimited capacity, no bay attached to it,
and that same unmeasured time
doesn't inflate your bay count at all.
I used to call these maintenance workshops.
Now I call the maintenance locations
because half the value is in the places maintenance happens
that were never a bay in the first place.
- Doesn't that mean you're still making assumptions?
Same problem as zero base?
- You're still making assumptions, sure,
but they're a different class of assumption.
Zero base assumptions are buried inside
100 individual task lines, easy to nudge one at a time
and never get caught.
The top down approach is just a handful of assumption
sitting out in the open with the largest impact bin
where does the residual maintenance go.
You can document those calls
and validate it against what you actually know about the site.
The great part is it's easy to review the list
and anyone can challenge it.
It's reasonable precisely because it's visible.
- All right Pete, time for the break tip.
- Okay, if you've got an expanding fleet
and need to calculate potential new workshop requirements,
use a top down approach and keep it simple
by identifying locations your maintenance happens.
Work with the team to define what happens at each location
and make reasonable assumptions
on the allocation to each space.
- And don't forget to capture those activities
that currently add to your demand.
While you may build a bigger workshop to eliminate these,
you need to know the impact they currently have.
- You don't have to over complicate it
to come up with a reasonable answer.
That's us for today.
If you found this episode useful,
like, subscribe, and share it with a mate.
Until next time, take care.
(upbeat music)
(upbeat music)
Podcast Summary
Key Points:
Two distinct methods—zero base buildup and top-down allocation—can both arrive at the same accurate workshop bay requirement.
The zero base method calculates total maintenance time by summing all scheduled tasks across assets, but relies heavily on assumptions about maintenance strategies and component work.
A major flaw in zero base is that it misses non-maintenance footprint needs like bay sterilization or equipment staging, which don’t appear in task lists but consume space.
Zero base assumptions can be manipulated to inflate bay demand, especially under pressure to justify larger workshops, making the result misleading.
The top-down method starts with actual fleet downtime as a factual baseline, then allocates known maintenance events to locations, leaving unmeasured work in a visible residual bucket.
The residual allocation is critical and requires transparent, justifiable assumptions that can be reviewed and challenged by stakeholders.
Top-down reduces risk by making assumptions visible and accountable, unlike buried assumptions in task-based models.
For expanding fleets, a simple top-down approach with clear location definitions and active team collaboration provides a reliable, transparent, and realistic workshop demand estimate.
Summary:
A maintenance workshop’s required bay count can be accurately determined through either a zero-base buildup or a top-down approach, with both methods arriving at the same result when done correctly. The zero-base method sums up all scheduled maintenance tasks across assets, but it depends on assumptions about work frequency and strategy, and fails to account for non-maintenance space needs like staging or equipment access. This can lead to inflated or underestimated demand if assumptions are subtly adjusted to meet pressures.
In contrast, the top-down method begins with real fleet downtime data—actual maintenance outages—as a factual baseline, then assigns known activities to specific locations, with unmeasured or unrecorded work placed into a visible residual category. This residual is key, as it captures unmeasured demand without inflating bay counts. The top-down approach is more transparent, with assumptions clearly defined and open to review, reducing the risk of hidden manipulation.
For expanding fleets, this method is recommended: it’s simpler, more realistic, and ensures that both current demand and future growth are understood through clear, collaborative site-based definitions. The takeaway is that accuracy and transparency matter more than complexity—simple, evidence-based methods deliver better outcomes.
FAQs
The zero base method builds bay demand from scratch by summing up all maintenance tasks—like tire changes or services—across every asset, multiplying frequency by duration, and assigning each to a maintenance location. It's thorough but depends heavily on accurate maintenance strategies and assumptions.
It often misses non-maintenance factors like bay sterilization or access needs for equipment. Since it only counts work time, not physical space requirements, it can underestimate actual bay demand and lead to under- or over-estimation if assumptions are not verified.
The top-down method starts with actual fleet downtime data and allocates known maintenance events to specific locations, then groups unmeasured or complex work into a 'residual' bucket, such as field repair or general maintenance.
It makes fewer, more visible assumptions that are open to review and challenge. Instead of hidden assumptions in hundreds of task lines, key decisions like residual allocation are clearly documented and validated against real site conditions.
The residual captures unmeasured maintenance work, like field repairs, that don't fit into specific bays. It's critical because it directly affects total bay demand and must be assigned logically to avoid inflating requirements.
Yes, but they should be transparent, documented, and reviewed. The top-down method reduces risk by keeping assumptions visible and subject to validation, unlike zero base where assumptions can be quietly adjusted to meet targets.
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