Maintenance planning and scheduling decides which maintenance work is done, when and by whom, within the hours your crew actually has and the windows in which the plant is available. Planning prepares the job: what needs doing and how. Scheduling puts prepared jobs on the calendar: when, and by whom. A good schedule contains only work that is ready to execute, leaves room for breakdowns and is measured afterwards, so it becomes a commitment that production and technicians can rely on rather than a wish list.
Maintenance planning and scheduling: two different questions
Planning is about the job itself: the scope, the steps, the hours per trade, the parts and the permit. That is work preparation, covered in detail in work preparation in maintenance. Scheduling is about the calendar: which jobs fit into this week's available hours, on which day, with which people, and when production will release the equipment.
| Aspect | Planning | Scheduling |
|---|---|---|
| Question | What and how? | When and who? |
| Output | Ready-to-execute work order | Weekly and daily schedule |
| Looks at | The job | Capacity and the plant |
| Typical role | Planner (work preparer) | Scheduler or supervisor |
The distinction matters. Scheduling work that has not been prepared means scheduling waiting time. Preparing work without looking at capacity builds a pile of ready jobs that nobody gets round to.
Planning and scheduling also work on several time horizons at once:
- A year or more ahead: shutdowns, statutory inspections and major preventive overhauls. A major outage is planned as a project in its own right; see shutdown and turnaround planning.
- Four to twelve weeks ahead: work that needs materials, a contractor or a downtime window, so that its preparation is finished in time.
- Next week: the weekly schedule, the core of this article.
- Today and tomorrow: who does what, and what moves after a breakdown.
The backlog: all the work still to be done
The backlog is all approved maintenance work that has not yet been carried out: corrective work that can wait, preventive tasks, inspection findings and small improvements. A request that has not been assessed does not belong in it. Work only counts once there is a work order with an estimated size.
Split the backlog in two:
- Ready to execute: scope and steps are known, hours are estimated, materials are in stock or reserved, permits and isolations are prepared, and it is clear whether the plant must be down.
- Not ready: the work is waiting for preparation, materials, a contractor or a downtime window. Give each work order its waiting reason as a status, so you can see where work gets stuck. If much of it is waiting for parts, look at how reservations and stock are tied to work orders, as described in spare parts management.
Measuring the backlog in weeks
The number of open work orders says little: twenty one-hour jobs are not the same as twenty overhauls. Count hours instead and set them against capacity:
Backlog in weeks = estimated hours of open work ÷ available hours per week
An example: a mechanical crew has 200 hours a week available. The total backlog is 920 hours, or 4.6 weeks of work. Of that, 460 hours are ready to execute: 2.3 weeks. Calculate this per trade, because an average across the whole department hides the fact that the electricians have three months of work and the fitters one week. Some teams divide by plannable rather than available hours; that is fine, as long as you always do it the same way.
The trend says more than a single reading. A backlog that grows month after month calls for a decision: more capacity, outsourcing or cutting work. Clean it up regularly too, because a work order that is a year old has often been dealt with already, is no longer needed or is a duplicate.
Prioritising: urgency and criticality
Not all ready work fits into one week, so you have to choose. Priority combines two questions: how soon must it happen (what happens if you wait), and how important is the equipment (what does a failure cost in safety, environment and production). The second part comes from an asset criticality analysis. Four levels are usually enough:
| Priority | When | Place in the schedule |
|---|---|---|
| 1 Immediate | Danger, or critical plant down | Breaks in at once |
| 2 Urgent | Failure likely within days | Within the current week |
| 3 Normal | Must be done, can wait | Next weekly schedule |
| 4 Low | Improvement or filler work | When there is room |
Define concrete criteria for each level and agree who assigns priorities. If requesters decide for themselves, everything becomes priority 1. Preventive maintenance on safety-critical equipment should never slip quietly. The UK HSE's technical guidance for major hazard sites names scheduled maintenance not being undertaken as required as a source of unrevealed failures of safety-critical items.
How to build a weekly maintenance schedule in seven steps
- Determine available capacity per trade. Count the people and hours you will really have next week, after leave, training and standing meetings. Count contractors working for you separately.
- Set aside a reserve for breakdowns and urgent work. Base it on your own figures: what share of hours over the past two or three months went to work that broke into the schedule? What remains are your plannable hours.
- Select only ready-to-execute work. Start with the highest priority and with preventive tasks due this week. For each job, check that materials are in, the permit is prepared, the downtime window is agreed and the contractor is confirmed.
- Load up to the plannable hours, not beyond. Look per day and per trade, not just at the weekly total, and allow for jobs that need two people at the same time. Group work on the same equipment so that one stop covers several jobs: if a packing line is down on Wednesday for a changeover, schedule that line's lubrication and inspection tasks there too.
- Agree the schedule with production. Review the draft in a fixed weekly meeting: which equipment is released when, and what has production planned itself? In a waste-to-energy plant, for example, that means work on a combustion line that can only go ahead once operations has taken the line out of service; in a distribution centre, the hours when the sorting system stands still. The same HSE guidance lists poor communication between maintenance and production staff as one of the issues that can contribute to a major accident.
- Freeze the week. After the meeting the schedule is fixed, preferably a few days before the week starts, so that the stores and the permit office can prepare.
- Schedule each day and measure. The supervisor allocates work daily and records what was finished, what was not and why. Those records feed next week's schedule.
The figure below shows the result for a mechanical crew of five technicians who are available all week. At eight hours each, that gives 40 hours a day and 200 hours a week. Over recent months an average of 15 per cent of hours went to urgent work, so the scheduler keeps 6 hours a day free and loads up to 34 hours a day: 170 plannable hours for the week. From the 460 hours of ready work, the scheduler builds a week of 164 hours: Monday 34, Tuesday 34, Wednesday 32, Thursday 34 and Friday 30. Wednesday and Friday keep a little slack, because the next jobs on the list need more hours than are left on those days.
On paper or in a spreadsheet, a capacity view per trade like this takes a lot of upkeep; you can see what it looks like on a digital planning board under maintenance planning software.
The frozen week and how to handle break-ins
A frozen week means the schedule no longer moves after the weekly meeting, except for genuinely urgent work. That is not bureaucracy. The stores have staged parts, permits have been prepared and production has released equipment on the basis of that schedule; reshuffling jobs midweek throws that preparation away. You also need a fixed baseline to measure afterwards what became of the plan.
Break-ins will still happen, so agree in advance:
- What may break in: only priorities 1 and 2. Anything that can wait until next week goes into the backlog.
- Who decides: the supervisor together with production, not the requester alone.
- What gives way: the lowest-priority work in the same trade. It stays ready to execute and goes to the top of next week.
- How it is recorded: every break-in gets a reason and hours. If the same failure keeps coming back, it is a candidate for root cause analysis, not for a bigger reserve.
Keep a small pool of filler work as well: ready-to-execute, low-priority jobs that need no shutdown or permit. If a scheduled job falls through because the equipment is not released after all or a part turns out to be wrong, the crew picks up filler work instead of waiting.
Not everyone works with a fixed reserve. Some organisations deliberately load all available hours and let urgent work push out the lowest-priority jobs. That works if you accept that schedule compliance will never reach 100 per cent, and if displaced jobs consistently go to the top of next week. Choose one approach and stick to it, or your figures will not be comparable.
Measuring schedule compliance, break-ins and backlog
Four measures tell you whether your schedule works:
| Measure | Calculation | What it tells you |
|---|---|---|
| Schedule compliance | Scheduled hours completed ÷ scheduled hours | Is the commitment met? |
| Break-in share | Urgent-work hours ÷ available hours | How reactive are you? |
| Backlog in weeks | Open hours ÷ hours per week | Is the work getting away from you? |
| PM compliance | PM orders done on time ÷ PM orders due | Is planned maintenance happening? |
Schedule compliance measures what share of the frozen schedule was completed in the scheduled week. Use the estimated hours of the completed jobs, or the number of work orders, and stick to one method. Work done outside the schedule does not count. Suppose the crew in the example completed 139 of the 164 scheduled hours: a schedule compliance of 85 per cent. In the same week, 34 hours went to urgent work, 17 per cent of the 200 available hours and so more than the 15 per cent reserve. The reasons behind the 25 hours left undone, such as urgent work beyond the reserve, jobs that overran or equipment that was not released, are worth more than the percentage itself.
Compare estimated and actual hours per job as well. Estimates that are consistently too tight make every schedule unachievable, and a better estimate costs nothing.
How to choose a small, useful set from all the maintenance KPIs is covered in maintenance KPIs. If you want a standard to benchmark against, EN 15341 lists key performance indicators for the maintenance function and gives guidance on choosing a suitable set.
Common mistakes in maintenance scheduling
- Loading full capacity without meaning to. Put 200 hours of work into 200 available hours and the first break-in wrecks the schedule; the crew soon learns that the schedule is not meant seriously. Time pressure is also a safety risk: EU-OSHA's basic rules for safe maintenance include allocating enough time and appropriate resources as part of good planning.
- Scheduling work that is not ready. Putting a job without parts or a permit into the week means scheduling waiting time.
- A task list without capacity. A list of what must happen this week, without the hours next to it, is not a schedule.
- No agreement with production. Work that needs the equipment down, scheduled without an agreement, gets called off on Monday morning.
- No feedback. If nobody records what was not done and why, next week repeats the same mistakes.
- The scheduler as firefighter. A scheduler who spends the day chasing breakdowns is not looking ahead. Protect the time to plan, especially when things are busy.
Frequently asked questions
What is the difference between a maintenance plan and a maintenance schedule?
A maintenance plan sets out, per asset, which tasks are needed and how often: lubrication every month, an inspection every 500 running hours, an overhaul every five years. A maintenance schedule decides when that work, together with corrective work and improvements, is actually carried out and by whom. The plan feeds work into the backlog; the schedule puts that work on the calendar. How to draw up the plan itself is explained in how to create a maintenance plan.
What does a maintenance planner or scheduler do?
A maintenance scheduler manages the backlog, builds the weekly schedule based on capacity and priority, agrees it with production and follows up on execution. After the week, the scheduler measures what became of the schedule and finds out why work was left undone. In many organisations the same person also prepares the jobs. In larger departments that is a separate planner role, so the scheduler can focus on the calendar and the planner on the job.
What is a good schedule compliance figure?
There is no single figure that holds for every organisation. A high score only means something if the schedule was properly loaded; anyone who schedules half the available hours will easily reach 100 per cent. Compare mainly with yourself: watch the trend over several months and the reasons why work was left undone. A rising line while the schedule stays just as full is the signal you are looking for.
What should you do with preventive maintenance that keeps being deferred?
Do not let deferral happen silently. Record who approves it and why, and put the work at the top of next week. If the same task keeps slipping, look for the cause: is capacity missing, is the equipment never released, or is the interval too short for what the task achieves? On safety-critical equipment, deferral should be a deliberate, recorded decision, with a temporary measure where needed.
Can you schedule maintenance in Excel?
Yes, for a small crew with manageable work Excel, another spreadsheet or a whiteboard can be enough. The limits appear once you want to see capacity per trade, track the status of hundreds of work orders, work with several schedulers or measure afterwards what became of the schedule. Keeping the spreadsheet up to date then becomes the job itself. A planning board that combines work orders, capacity and history takes that over.