Shift planning in industry: a roster without gaps

Shutting down a production line because nobody is rostered on the night shift costs more than a day's turnover. Yet that is exactly what happens when a shift roster is built too tight: one sick call on a Sunday evening and the whole puzzle falls apart. Planning shift work is therefore above all an exercise in building in margin — within the limits set by Belgian labour law.

In this article we run through the most commonly used shift systems, the legal conditions you cannot get around, and how to build a roster that survives an ordinary working week including setbacks.

What makes shift work legally different?

In shift work, teams relieve one another at the same post without the activity coming to a halt. That is precisely why labour law allows derogations here from the normal daily and weekly limits: shifts of 8, 10 or 12 hours become possible, even though the standard is 8 hours a day.

Three things do remain in force:

• An average of 38 hours per week (or the shorter working time set in your sectoral collective labour agreement), measured over a reference period. The default is a quarter, but the reference period can be extended to up to a year via a collective labour agreement or the work rules.
• At least 11 consecutive hours of rest per 24-hour period, between two periods of work (FPS Employment, Labour and Social Dialogue on rest periods).
• A break as soon as working time exceeds 6 hours, with the duration and arrangements laid down in a collective labour agreement or the work rules.

And this is crucial in practice: the shift rosters must be set out in your work rules. In principle you may not use a roster that does not appear there. So if you introduce a new system — an additional weekend shift, for example — that requires an amendment to the work rules, along with the accompanying procedure.

The classic systems — and how many people you really need

Always calculate in hours per post first, not in headcount. The arithmetic is simple and sobering.

Two-shift system (early/late, 5 days)
2 shifts × 8 hours × 5 days = 80 hours per week per post. Divided by 38 hours: roughly 2.1 FTE per post.

Three-shift system (5 days, night included)
3 × 8 × 5 = 120 hours per week per post, or roughly 3.2 FTE.

Fully continuous (24/7)
168 hours per week per post, divided by 38 = 4.42 FTE. That is why almost nobody works with four shift teams: in practice you need a fifth team to cover leave, training, sickness and compensatory rest.

That 0.42 or 0.8 FTE you are short of is not an accounting detail. It is exactly the reason why managers start phoning people on a Friday evening. Plan with four teams in a continuous system and you will structurally make up the difference with overtime — running straight into the internal limit and the compensatory rest that comes with it.

Build your roster in four steps

1. Start from production needs, not from the current roster

Map out week by week which lines or posts have to be staffed, and with which qualifications. In doing so, distinguish between:

• posts that may never be left unstaffed (safety, continuous process, forklift requiring a certificate)
• posts you can postpone for half a shift
• tasks you deliberately shift to the early team (maintenance, quality control)

This breakdown determines later on which gaps you fill urgently and which you simply let run.

2. Choose a cycle and keep it predictable

A shift cycle that repeats every 4, 5 or 10 weeks is far more valuable to your people than a roster that is reinvented every month. Predictability reduces swap requests, and swap requests are precisely what makes your planning expensive.

When drawing it up, check every time: how many hours are in the cycle, does the 38-hour average work out over the reference period, and does every changeover respect the 11 hours of rest? The classic pitfall is the switch from late to early shift: finishing at 10 p.m. and starting again at 6 a.m. is 8 hours of rest — that is not allowed.

3. Build in the replacement layer

Who replaces whom? Set that out before anything happens:

• a list of employees by qualification, showing who can take over which post
• a fixed reserve or "flex team" that is not rostered on a line
• agreements on who gets contacted first, and how

If you use agency workers to cover peaks and gaps, the administrative lead time counts as part of your planning. In scheduling agency workers in logistics we describe that approach; in industry it works largely the same way, with qualifications and safety instructions as an extra filter.

4. Record straight away, not afterwards

With shift work, the difference between planned and actual hours mounts up quickly: a shift that overruns by 40 minutes because the relief is late happens dozens of times a quarter. If you do not record it, at the end of the reference period you will not know whether you are staying within the average working time — and you will be arguing with the trade union delegation on the basis of recollections.

With digital time registration, planned and actual hours sit side by side, per team and per employee. That turns planning compensatory rest into a decision rather than a guess.

Premiums, night work and the cost side

Shift and night premiums are set in your sectoral collective labour agreement, not in labour law. In industry, the percentages and the conditions therefore differ from one joint committee to another: check which premium applies to the early, late and night shift, and whether separate amounts exist for weekend or fully continuous work.

What you feel in the planning: the same 8 hours does not cost the same everywhere. Starting a line up an hour earlier may shift the entire shift into a premium band. Visibility on your wage cost per shift turns such choices into a conscious trade-off.

If you work at night, also read night work and premiums: what Belgian law says. And for the eternal July–August debate: managing leave requests in shift work.

Five mistakes that wreck your roster

1. Planning with exactly 4 teams in a continuous system. A structural shortfall, structural overtime.
2. Using rosters that are not in the work rules. During an inspection, that is the first thing you will be asked for.
3. Changeovers without 11 hours of rest. This slips through the net especially when colleagues swap shifts among themselves.
4. Losing sight of the reference period. Overtime you only spot in month three can hardly be compensated any more.
5. Not keeping qualifications up to date. A filled shift with the wrong certificates is an empty shift.

From firefighting to a roster with margin

A good shift roster acknowledges that things go wrong. It contains reserve capacity, a clear replacement logic and a recording system that tells you every week how far you are from your average. That is less spectacular than a perfectly drawn cycle, but it is exactly what keeps a line running.

Want to see what that looks like in concrete terms for your own site? Take a look at our approach for industry and production and for the HR administration that sits underneath it.