A 12 hour shift roster that runs four shifts on and four days off averages 42 hours a week, which is four hours above the 38 hours a week that the Fair Work Act treats as the full-time maximum unless extra hours are reasonable. This guide covers Victorian workplaces and tests the pattern against that arithmetic, two awards and WorkSafe Victoria's fatigue guidance.
What 4 on 4 off actually adds up to
In a 4 on 4 off roster, an employee works four 12 hour shifts in a row and then has four days off, and the cycle repeats every eight days. Four crews on 12 hour shifts is the classic setup for round-the-clock cover. The crew arithmetic for that is covered in a separate guide on 24 hour roster crews, so this guide stays with the shift pattern.
The weekly arithmetic
Here is the arithmetic. Four shifts of 12 hours is 48 hours in each eight-day cycle. Divide by eight days and multiply by seven, and the average is 42 hours a week, or three and a half shifts a week.
That is four hours a week above 38. Under the Fair Work Act (section 62), an employer must not request or require a full-time employee to work more than 38 hours in a week unless the additional hours are reasonable. A modern award or enterprise agreement can average hours over a period (section 63), but hours above 38 worked under an averaging term are still treated as additional hours, and the averaging term is one factor in deciding whether they are reasonable. The extra hours do not disappear, so check whether your award or agreement deals with them through averaging, accumulated rostered days off or overtime.
Check your award before anything else
The Manufacturing and Associated Industries and Occupations Award 2020 says it covers employers throughout Australia of employees in the Manufacturing and Associated Industries and Occupations who are covered by its classifications, and the Storage Services and Wholesale Award 2020 says it covers employers throughout Australia in the storage services and wholesale industry (both clause 4.1). Check which award or enterprise agreement covers your people.
- Manufacturing, 12 hour shifts. Under the Manufacturing Award 2020, 12 hour days or shifts can be introduced by agreement between the employer and the majority of employees, with conditions (clause 17.5(c)). The conditions are health monitoring, suitable roster arrangements, proper supervision, adequate breaks, and a trial or review process run jointly with employees.
- Manufacturing, ordinary hours. If your people are covered by it, the Manufacturing Award 2020 sets ordinary hours for continuous shiftworkers (clause 17.3) and non-continuous shiftworkers (clause 17.4) at an average of 38 a week, with no more than 8 per shift unless agreed under clause 17.5 (clauses 17.3(c) and (d), 17.4(b) and (c)). Clauses 17.3 and 17.4 do not apply to vehicle manufacturing employees covered by clause 4.8(a)(xi) (clauses 17.3(a) and 17.4(a)). The same award lists accumulation of rostered days off among the matters that can be agreed (clause 17.5(b)(vi)), and deals with overtime in clause 32.
- Storage. Under the Storage Services and Wholesale Award 2020, shiftworkers' ordinary hours are not to exceed 8 in a day, or up to 10 by agreement (clause 20.3). Time worked beyond ordinary hours is overtime (clause 21.1(a)).
The Fair Work Ombudsman's award library publishes both, including the Manufacturing Award 2020 and the Storage award.
What WorkSafe Victoria says about long shifts
WorkSafe Victoria's work-related fatigue guide for employers treats shift length as a hazard to control. The WorkSafe fatigue guidance page carries its risk approach, and its control measures bear directly on a 12 hour roster:
- Cap the shift. Limit shifts to 12 hours, including overtime.
- Cap the week. Minimise weekly work hours to 48 hours or less.
- Protect recovery. Try to have at least 12 hours between shifts, and give shift workers consecutive days off, including some weekends.
On manual tasks, WorkSafe says the risk of a musculoskeletal injury is significantly higher during a 12-hour shift than during an eight-hour shift, and that injuries usually occur towards the end of a shift.
Rules that make a 12 hour roster safer to run
A 4 on 4 off roster at 42 hours a week sits under WorkSafe's 48 hour weekly guide, but a 12 hour shift already uses all of WorkSafe's 12 hour shift limit, leaving no room for hold-overs. Write these rules down and apply them to every shift:
- No hold-overs past 12 hours. Count handover and overtime inside the 12 hours.
- Protect the gap between shifts. For example, a 6 am to 6 pm shift followed by a 6 am start leaves exactly 12 hours with no allowance for travel, so any late finish breaks WorkSafe's target of at least 12 hours.
- Control swaps. A swap that puts someone on a fifth shift in a row, or a second shift inside 24 hours, defeats the roster.
Example: covering one absence without a 14 hour shift
Here is an example with illustrative numbers. A day crew works 6 am to 6 pm and one picker calls in sick at 5 am. Asking a colleague to stay until 8 pm would make a 14 hour shift, past WorkSafe's 12 hour limit. A prepared cover list is the better answer, so a casual or labour hire worker who has had the site induction can fill the gap. If you have not yet chosen the kind of cover to use, the post on choosing between casual, fixed-term and labour hire engagement sets out the tests under the Fair Work Act.
Trial it with a review date
Under any award, treat the move as a trial. Set a review date after a full cycle of rotations, and decide in advance what would make you stop.
- Hours and hold-overs. Actual hours per person, including overtime, and how often someone stayed past 12 hours.
- Injuries and near misses. The point in the shift when each one happened.
- Absence, swaps and feedback. Whether unplanned absences and swap requests rise, and what crews say about sleep and travel.
Treat the pattern with extra caution where the work is physically heavy (WorkSafe flags higher injury risk in a long shift), where absences cannot be covered inside WorkSafe's 12 hour limit, or where your award or enterprise agreement does not support it. A separate guide on fixed and rotating rosters compares other patterns.
Chandler Personnel is available 24 hours a day because blue collar staffing changes hour to hour, and it runs site inductions on behalf of clients, so a client can ask the provider to cover the shift rules in the induction. It supplies labour hire for manufacturing and production sites and for warehousing and logistics operations.
If your roster runs through the night, the post on 24/7 shift safety covers night shift fatigue during peak periods, and the post on hiring night shift trades covers recruiting maintenance tradespeople for night work.
Related Resources
- Manufacturing and production labour hire
- Warehousing and logistics staffing
- 24/7 shift safety
- Hiring night shift trades
- Fixed-term, casual and labour hire options
- WorkSafe fatigue guidance
- Manufacturing Award 2020
Common Questions About 12 Hour Shift Rosters
1. How many hours a week is a 4 on 4 off roster?
A 4 on 4 off roster averages 42 hours a week. Four 12 hour shifts is 48 hours in an eight-day cycle, and 48 divided by 8, multiplied by 7, is 42. That is above 38, so check how your award or agreement treats the extra hours.
2. Can I put employees on 12 hour shifts under my award?
It depends on the award or enterprise agreement that covers your people. The Manufacturing Award 2020 allows 12 hour shifts by agreement with the majority of employees, with conditions (clause 17.5(c)). The Storage Services and Wholesale Award 2020 limits shiftworkers' ordinary hours to 8 a day, or up to 10 by agreement (clause 20.3).
3. Are 12 hour shifts unsafe?
They carry added risk that you need to control. WorkSafe Victoria says the risk of a musculoskeletal injury is significantly higher during a 12-hour shift than during an eight-hour shift. Its fatigue guide recommends limiting shifts to 12 hours including overtime.
4. How much rest is needed between 12 hour shifts?
WorkSafe Victoria's fatigue guide for employers says to try to have at least 12 hours between shifts. On a 6 am to 6 pm roster, a 6 am start the next day leaves exactly 12 hours with no allowance for travel. Your award may add its own rest rules, so check it too.
5. What happens to overtime on a 12 hour roster?
It depends on the award. The Manufacturing Award 2020 deals with overtime in clause 32, and the Storage Services and Wholesale Award 2020 treats time worked beyond ordinary hours as overtime (clause 21.1(a)). Read the overtime clause in your own award or agreement before you roster.
Trial 12 hour shifts before committing to them
A 12 hour shift roster trades longer shifts for longer breaks, and the cost shows up in fatigue, injury risk and award conditions. Do the arithmetic, read the clause that applies to your people and write the hold-over rules down. Then run a trial with a review date.
