# Night shifts for agency temps: the 8-hour average over 17 weeks, the free health assessment, and five shift patterns checked

> Night workers average no more than 8 hours in 24 over 17 weeks and must be offered a free health assessment. Five 12-hour and 10-hour night patterns tested.

- Page to cite: https://aeolookup.com/recruitment/night-worker-8-hour-average-17-weeks-health-assessment-recruitment-agency-shift-patterns-worked/
- Publisher: AEO Lookup (https://aeolookup.com/)
- Section: Recruitment agencies, AWR, right to work and the Conduct Regulations
- Published 29 October 2026
- Key fact: Over a 17-week reference period (119 days) the weekly hours that hit an average of 8 in 24 are 56 if every day is counted, or 48 if one rest day a week is taken out (102 days, 816 hours). Five patterns tested both ways. 3 x 12 hours, 36 a week: 612 hours, 5.14 and 6.00 a day. 4 x 12, 48 a week: 816 hours, 6.86 and 8.00. 5 x 10, 50 a week: 850 hours, 7.14 and 8.33. 6 x 9, 54 a week: 918 hours, 7.71 and 9.00. 5 x 11, 55 a week: 935 hours, 7.86 and 9.17. Only the first two pass on both counts; the last three pass only if rest days are not taken out.
- Sources: GOV.UK, "Night working hours" (https://www.gov.uk/night-working-hours) and its sub-page "Health assessments" (https://www.gov.uk/night-working-hours/health-assessments). A night worker regularly works at least 3 hours during the night period; night time is 11pm to 6am unless a different 7-hour period including midnight to 5am is agreed in writing. A night worker's average working time must not exceed 8 hours in any 24-hour period; regular overtime counts towards the average, occasional overtime does not, and workers cannot opt out. The average is usually calculated over 17 weeks, or up to 52 weeks by agreement such as a collective agreement. Workers on special-hazard or high-strain work must not exceed 8 hours in any 24-hour period, with a risk assessment. Employers must offer a free health assessment before a worker becomes a night worker and regular assessments afterwards; the worker does not have to accept; if a health professional confirms night work has affected health the employer must, where possible, offer other suitable work; confidential records are kept for 2 years, with the dates of any declined offers. Workers aged 16 and 17 generally cannot work between 10pm and 6am (contract can move this to 11pm to 7am) and not at all between midnight and 4am, with listed exceptions. I did not read the page on exceptions to the night work limits, the Working Time Regulations 1998 or any rule on how rest days enter the 17-week average, so the two counts below are bounds, not a legal ruling. Read 29 October 2026.

A warehouse client wants temps on 12-hour night shifts. The desk thinks the night limit is 8 hours a shift and says no. GOV.UK says something different: the limit is an average of 8 hours in any 24-hour period, usually over 17 weeks. A 12-hour night can sit inside it. This guide tests five patterns against that average.

## What GOV.UK says

- **Who is a night worker.** Someone who regularly works at least 3 hours during the night period. Night time is 11pm to 6am by default; a different 7-hour period that includes midnight to 5am can be agreed in writing.
- **The limit.** Average working time must not exceed 8 hours in any 24-hour period. Regular overtime counts towards the average; occasional overtime does not. Workers cannot opt out.
- **The reference period.** Usually 17 weeks. Up to 52 weeks can be agreed, for example in a collective agreement.
- **Special hazard or high strain.** The page says these workers must not exceed 8 hours in any 24-hour period, and a risk assessment is needed.
- **Health assessment.** The employer must offer a free assessment before the worker becomes a night worker, and regular ones afterwards. The worker does not have to accept. If a health professional confirms night work has affected their health, the employer must, where possible, give other suitable work. Records are confidential and kept for 2 years, including the dates when an offer was declined.
- **Under 18s.** Workers aged 16 and 17 generally cannot work between 10pm and 6am (the contract can move it to 11pm to 7am), and cannot work between midnight and 4am, with exceptions listed on the page.

## Five patterns against the 8-hour average

The page does not say how rest days enter the average, so I give two counts and treat them as bounds.

- **Count A, every day counted:** 17 weeks is 119 days. Total hours divided by 119.
- **Count B, one rest day a week taken out:** 119 - 17 = 102 days. Total hours divided by 102. This is my assumption about the stricter reading, not something the page states.

At 8 hours a day the ceilings are 8 x 119 = 952 hours (Count A, which is 56 hours a week) and 8 x 102 = 816 hours (Count B, which is 48 hours a week).

| Pattern | Hours a week | Hours in 17 weeks | Average a day, Count A (/119) | Average a day, Count B (/102) |
|---|---|---|---|---|
| 3 x 12 hours | 36 | 612 | 5.14 | 6.00 |
| 4 x 12 hours | 48 | 816 | 6.86 | 8.00 |
| 5 x 10 hours | 50 | 850 | 7.14 | 8.33 |
| 6 x 9 hours | 54 | 918 | 7.71 | 9.00 |
| 5 x 11 hours | 55 | 935 | 7.86 | 9.17 |

Checked twice: 36 x 17 = 612; 48 x 17 = 816; 50 x 17 = 850; 54 x 17 = 918; 55 x 17 = 935. Then 612 / 119 = 5.14 and 612 / 102 = 6.00; 816 / 119 = 6.86 and 816 / 102 = 8.00; 850 / 119 = 7.14 and 850 / 102 = 8.33; 918 / 119 = 7.71 and 918 / 102 = 9.00; 935 / 119 = 7.86 and 935 / 102 = 9.17.

What it shows:

- **Shift length is not the test.** Four 12-hour nights a week sits at 6.86 on Count A and exactly 8.00 on Count B.
- **Only the first two patterns pass on both counts.** The 5 x 10, 6 x 9 and 5 x 11 patterns look short on a single night but pass only if rest days are not taken out. Where a client runs them, get the rule on rest days confirmed before the rota is signed.
- **Regular overtime moves a pattern down this table.** A 4 x 12 temp who regularly does a fifth night is on 60 hours a week: 1,020 hours, 8.57 on Count A (1,020 / 119) and 10.00 on Count B (1,020 / 102).

## What this means on the desk

- **Ask the client for the pattern in weeks, not shifts.** The test is the 17-week total, so ask for the rota and the usual overtime, not just the shift length.
- **Offer the health assessment before the first night and record the offer.** Note the date, and note a refusal. The worker may decline, but the date of the offer is what you keep, for 2 years.
- **Keep under-18s off the pattern.** Check dates of birth against the 10pm to 6am and midnight to 4am limits before a night booking.
- **Cost it.** Night hours may carry a premium under the temp's contract or the client's pay scale. Run the new rate through the [temp margin calculator](https://aeolookup.com/recruitment/temp-margin-calculator-charge-rate-employer-costs/). The weekly cap and the day-to-day rest rules are set out in the [48-hour week guide](https://aeolookup.com/recruitment/temp-48-hour-week-limit-17-week-average-opt-out-recruitment-agency-worked/) and the [rest breaks and rota guide](https://aeolookup.com/recruitment/temp-rota-rest-breaks-20-minutes-11-hours-daily-rest-24-hours-weekly-rest-agency-worked/).

## What the pages do not say

They do not say how rest days enter the 17-week average, which is why the table gives two counts. I did not read the page on exceptions to the night work limits, the Working Time Regulations 1998, or any guidance on who must offer the assessment when a temp is supplied through an agency. Confirm those before you sign off a rota.

Overlyft ![](https://aeolookup.com/img/d/ours-badge.png) builds AI staff who join your placements team and, when a client sends a night rota, total the 17 weeks for each temp, flag any pattern over the line and draft the health assessment offer, all queued for a person to check and send.

This is general information, not legal or payroll advice. Check GOV.UK and the Working Time Regulations 1998 before you rely on a rota.

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General information for UK small firms, not legal, tax or financial advice.