One post needing round-the-clock cover requires 168 hours per week. That means roughly 5 guards per post once holidays, sickness and training are factored in — not the 4.2 that the raw maths suggests. Pick a proven rotating pattern such as 4-on-4-off or Pitman 2-2-3, publish it weeks in advance, and build your relief cover and legal compliance in from day one.
Key takeaways
- 24/7 cover = 168 hours per week per post. Divide by contracted weekly hours, then multiply by a relief factor of 1.1–1.3 — the result is your real headcount.
- For a single 24/7 post, budget for 5 full-time guards, not 4.
- 4-on-4-off (12-hour shifts) is the UK security industry standard; Pitman 2-2-3 is the best alternative for retention, with a 3-day weekend every other week.
- Every 12-hour rotating pattern averages 42 hours per week — bake that structural overtime into your charge-out rates.
- Publish rotas 2–4 weeks ahead; fixed patterns let guards plan months out.
Step 1: Calculate how many guards you actually need
This is where most rota problems start. The basic formula is simple:
Guards needed = (total cover hours per week ÷ average hours per guard per week) × relief factor
For a single post with continuous cover:
- 168 — total hours in a week (24 × 7)
- 40 — typical full-time contracted hours per guard
- 4.2 — full-time equivalents needed before anyone takes a holiday or calls in sick
4.2 is a floor, not a plan. No real operation runs with zero absence, so you apply a relief factor that covers annual leave, sick days, SIA training days and everything else that takes a guard off the rota:
| Relief factor | Suits | Guards per 24/7 post |
| 1.1 | Low-absence environments, minimal time off | 4.6 → 5 |
| 1.2 | Typical operations with standard leave and sickness | 5.04 → 5 |
| 1.3 | High-absence environments or roles needing extensive training | 5.5 → 6 |
Always round up. You cannot roster 0.04 of a guard, and running at exactly 4.2 means the first sick day leaves a post uncovered — a contract breach and, on an SIA-licensed site, potentially a compliance incident.
If you run 12-hour shift patterns (see below), guards average 42 hours per week, so the base figure is 168 ÷ 42 = 4.0 FTE — but the relief factor still takes you to roughly 5 guards per post. The answer barely changes; the pattern does.
Scale it up for multi-post contracts:
| Posts on 24/7 cover | Weekly hours | Guards needed (×1.2 relief) |
| 1 | 168 | 5 |
| 2 | 336 | 10 |
| 3 | 504 | 15–16 |
| 5 | 840 | 25–26 |
Knowing your true headcount also matters for pricing: every guard on the rota has to be covered by the contract’s charge-out rate, including the relief cover you will inevitably pay for.
Step 2: Choose your shift pattern
A shift pattern is the repeating cycle that decides who works when. For 24/7 security cover, five patterns do almost all the heavy lifting. All the 12-hour options average 42 hours per week — the difference is how those hours are distributed, who gets weekends, and how tiring the cycle is.
| Pattern | Shift length | Teams | Cycle | How it works | Best for |
| 4-on-4-off | 12 hours | 4 | 8 days | Four shifts on, four days off. Two teams work (day/night) while two rest. | UK security standard — simple, predictable, guards love the 4-day breaks |
| Pitman (fixed 2-2-3) | 12 hours | 4 | 14 days | 2 on, 2 off, 3 on, 2 off, 2 on, 3 off. Fixed days/nights. Never more than 3 shifts in a row. | Retention — a 3-day weekend every other week |
| Panama (rotating 2-2-3) | 12 hours | 4 | 28 days | Same 2-2-3 sequence as Pitman, but teams rotate between days and nights every two weeks. | Fairness — nights shared equally across all teams |
| DuPont | 12 hours | 4 | 28 days | 4 nights, 3 off, 3 days, 1 off, 3 nights, 3 off, then 7 consecutive days off. | Guards who want a full week off every month; hard on sleep from the day/night switches |
| Continental | 8 hours | 4 | 28 days | Three 8-hour shifts (early/late/night) rotating across four teams. | Sites where 12-hour shifts are unsuitable, e.g. high-concentration monitoring roles |
Which pattern should a security firm choose?
- Default choice: 4-on-4-off. It is the pattern UK security officers know and expect, it is trivial to administer, and the 8-day cycle means rotas practically build themselves.
- If retention is a problem: Pitman. The guaranteed 3-day weekend every other week and maximum of three consecutive shifts make it the kindest 24/7 pattern on the list.
- If nights cause resentment: Panama. Rotating everyone through nights feels fairer than permanent night teams — but forward-rotating (days → nights) causes less fatigue than backward rotation.
- Avoid DuPont unless your guards specifically ask for it: the 72-hour week and rapid day/night switches sit badly with working-time compliance
Step 3: Build the rota — a worked example
Let’s put it together: one site, one post, 24/7 cover, 4-on-4-off, 12-hour shifts (07:00–19:00 days, 19:00–07:00 nights).
From Step 1 you need 5 guards. You organise them into four teams (A, B, C, D) plus one relief guard. Here’s how an 8-day cycle looks:
| Day | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Day shift (07:00–19:00) | A | A | A | A | C | C | C | C |
| Night shift (19:00–07:00) | B | B | B | B | D | D | D | D |
| Resting | C, D | C, D | C, D | C, D | A, B | A, B | A, B | A, B |
The fifth guard is your relief/floater: they cover annual leave, sickness, training days and SIA licence renewal appointments, and step in for no-shows. On quiet weeks they can pick up ad-hoc shifts at other sites or take on supervisor checks — they should never be treated as spare capacity to cut.
Rules that keep this rota healthy:
- Publish 2–4 weeks ahead. Fixed patterns mean guards can plan months out — advertise that in recruitment.
- Fix handovers at the same times daily (e.g. 07:00 and 19:00) so shift briefings become routine, not negotiations.
- Rotate the relief guard fairly — don’t let the floater become a permanent night-shift dumping ground.
- Track hours in real time, not at payroll: a guard picking up relief shifts can breach the 48-hour weekly average before you notice.
Step 4: Bake in legal compliance
A rota that breaches the Working Time Regulations 1998 is a liability, not a plan. The non-negotiables for UK security employers:
- 48-hour average working week — averaged over 17 weeks. All 12-hour patterns average 42 hours, which is compliant, but relief and overtime shifts can push individuals over. Guards can voluntarily opt out in writing, but you cannot force or incentivise it.
- Night workers: 8-hour average per 24 hours — averaged over 17 weeks, and the limit is absolute (no opt-out) for work involving special hazards or heavy physical strain. Night guards also get free health assessments.
- 11 hours’ daily rest between shifts and 24 hours’ weekly rest (or 48 per fortnight).
- 20-minute uninterrupted break for any shift over 6 hours.
- Security and surveillance roles can qualify for limited “special case” flexibility — but any derogation must be replaced with compensatory rest.
We cover every rule in detail — including how 12-hour shifts interact with rest breaks, and the landmark case law on compensatory rest — in our guide to 12-hour security shifts: rest breaks and working time rules.
Two more compliance points for rota builders:
- SIA licensing: every guard on the rota must hold a valid SIA licence for the role. Build licence-expiry checks into your scheduling process — a guard whose licence lapses mid-rota cannot legally work. See our guide to tracking SIA licences across 50+ guards.
- Right to work and BS 7858 screening: relief guards pulled in at short notice still need full vetting. Keep a pre-vetted relief pool rather than scrambling.
Step 5: Plan for absence, holidays and no-shows
Your rota is only as strong as its cover plan. Build three layers:
- The relief factor (structural). The 1.2 multiplier from Step 1 means you employ ~5 guards per post, not 4.2. This is your first line of defence and it is already in the budget.
- A relief pool (tactical). Part-time and zero-hours guards who know your sites, hold valid SIA licences and have completed site inductions. Aim for 10–15% of your rostered headcount as available relief.
- A no-show protocol (emergency). Define it in writing: who gets called first, escalation to the supervisor after 30 minutes, and a hard rule that a post is never left uncovered — including who authorises emergency overtime rates.
Set overtime guardrails too. Structural overtime (the built-in 8 hours every other week on 12-hour patterns) is predictable and should be priced into contracts. Unplanned overtime from absence is where margins leak: cap consecutive overtime shifts, require supervisor approval above a threshold, and review overtime hotspots monthly — a post that constantly needs cover usually has a rostering or retention problem, not a staffing problem.
7 Rota Mistakes That Cost Security Firms Money
- Rostering exactly 4.2 FTE per post. The first sick day breaks the rota. The relief factor is not optional.
- Treating the relief guard as spare capacity. The moment you cut the floater to “save money”, absence cover becomes premium overtime.
- Backward rotation (nights → days). Forward rotation (days → nights) is consistently easier on sleep and health.
- Publishing the rota days before it starts. Late rotas drive no-shows and resignations. Two to four weeks is the minimum.
- Ignoring the 48-hour average. Relief shifts quietly push guards over the limit — track cumulative hours, not just this week’s rota.
- Scheduling guards with expiring SIA licences. One lapsed licence mid-contract can void your cover and breach client terms.
- Running rotas on spreadsheets. Spreadsheet rotas don’t flag expiring licences, overtime breaches or unconfirmed shifts — and they collapse the moment your scheduler is off sick.
How Rota Software Handles This Automatically
Building a 24/7 rota by hand means juggling headcount maths, pattern cycles, licence expiries, overtime limits and last-minute swaps across every site. BookOn Solutions is built specifically for UK security firms to take that load:
- AI-assisted scheduling that builds rotas around your chosen pattern, site requirements and guard availability.
- Mobile app shift confirmations — guards accept shifts on their phones, so you know instantly what’s covered.
- Overtime and compliance alerts before a guard breaches working-time limits, not after payroll.
- SIA licence and expiry tracking linked to scheduling, so an unlicensed guard can never be rostered.
- Real-time visibility across every site, post and relief pool from one dashboard.
See how it fits your operation on the pricing page, or book a demo to watch a 24/7 rota build itself.
Conclusion
A reliable 24/7 security rota comes down to five things: honest headcount maths (5 guards per post, not 4.2), a proven pattern your guards actually want to work, legal compliance built into the cycle, a relief plan for the inevitable absences, and software that holds it all together. Get those right and the rota stops being a weekly firefight — it becomes a selling point in your next contract bid.
Book a demo of BookOn Solutions and see a 24/7 rota build itself in minutes.