Maintenance Backlog: Formula and Public-Sector Plans

What maintenance backlog means

Maintenance backlog has two meanings. In maintenance management it is the approved work not yet done, usually expressed in crew-weeks of labour. In public-sector estates it means deferred maintenance: the estimated cost of the work needed to bring buildings and infrastructure up to an acceptable condition. It matters because a growing backlog of either kind turns into closures, safety incidents and larger capital bills later.

The two measures answer different questions. Crew-weeks tell an operations manager whether the team can keep up this quarter. Deferred maintenance cost tells a council, ministry or hospital board how far the estate has fallen behind and what it will cost to recover. This guide shows how to calculate both, how to rank the work by risk, and how to turn the result into a multi-year plan and budget. Figures are stated as of October 2026.

The public numbers: hospitals, schools and municipal infrastructure

The UK publishes the clearest backlog data. NHS trusts reported through the Estates Returns Information Collection (ERIC) for 2024/25, published on 16 October 2025, an estimated £15.9 billion to eradicate backlog maintenance, against £13.8 billion in 2023/24, a rise of about £2.1 billion in a year; ERIC notes that the backlog figure excludes planned maintenance. The Department of Health and Social Care's 10 Year Capital Plan, published on 8 July 2026, puts the backlog in the NHS secondary-care estate at £4.9 billion in 2015-16, says it has more than tripled since 2015 with the highest-risk categories rising fastest, and reports over 4,100 service-disruption incidents from estates failures in the last year.

For schools in England, the National Audit Office reported in June 2023 that around 24,000 school buildings, 38 per cent, were beyond their estimated initial design life. The Department for Education spent on average £2.3 billion a year from 2016-17 to 2022-23, 76 per cent of it on maintenance and repair; it had recommended £5.3 billion a year and requested £4 billion, and HM Treasury allocated an average of £3.1 billion. The NAO found funding was often used for urgent repairs rather than planned maintenance, which risks poor long-term value.

In Canada, the Canadian Infrastructure Report Card 2019 stated that a concerning amount of municipal infrastructure is in poor or very poor condition and will need rehabilitation or replacement in the next 5 to 10 years. The pattern is the same everywhere: when budgets are short, reactive repairs crowd out planned work, and the deferred bill grows faster than the budget.

Backlog formula 1: crew-weeks of open work

The operational backlog formula is: backlog in weeks = estimated labour hours of approved, open work ÷ productive labour hours available per week. Include only work that is approved and ready or waiting for parts; exclude requests not yet triaged, and keep planned maintenance not yet due out of the figure.

Worked example. A council's building maintenance team has 2,880 estimated hours of approved open work. It has 12 technicians working 37.5 hours a week, of which 80 per cent is productive time on jobs: 12 × 37.5 × 0.8 = 360 productive hours a week. The backlog is 2,880 ÷ 360 = 8 weeks.

The trend matters more than the level. If 380 hours of new work arrive each week and the team completes 360, the backlog grows by 20 hours a week, or 20 × 52 = 1,040 hours a year, about 2.9 more weeks of backlog by next year. There is no universal target; set one per trade from your own history and from how long a routine job can safely wait.

Backlog by age and priority

A single number hides the risk. Break open work orders down by age and by priority every month. Worked example: a district has 420 open work orders, of which 210 are up to 30 days old, 130 are 31 to 90 days old, 50 are 91 to 180 days old and 30 are older than 180 days (210 + 130 + 50 + 30 = 420).

The 30 oldest jobs deserve a line-by-line review. Some will be duplicates or no longer needed and should be cancelled with a reason; some are waiting for parts or access and need a named owner; and any high-priority job in that bucket is a governance problem, because it means a risk was accepted without anyone deciding to accept it. A backlog report that shows age by priority, by site and by trade turns those decisions into a monthly routine.

Backlog formula 2: deferred maintenance cost

The estate-level measure is the estimated cost of the work needed to bring each building or network to the condition the organisation has set as acceptable, usually from a condition survey. Divide it by the current replacement value of the same assets to compare estates of different sizes; this ratio is a management indicator you define, so state the method alongside it.

Worked example in EUR. A municipality's 20 buildings have a current replacement value of €80 million. Condition surveys put the deferred maintenance cost at €6.4 million, which is 6.4 ÷ 80 = 8 per cent of replacement value. Split by risk, the backlog is:

• High risk (illustrative definition: could cause serious failure, injury or closure within a year): €1.2 million
• Significant risk: €2.0 million
• Moderate risk: €2.2 million
• Low risk: €1.0 million
• Total: 1.2 + 2.0 + 2.2 + 1.0 = €6.4 million

Ranking the work: risk, criticality and value

Not every item in the backlog deserves money this year. Score each item on two axes, the likelihood of failure (1 to 5) and the impact of that failure on services, safety and compliance (1 to 5), and multiply them. Then divide the cost by the score to see how much risk each euro removes. Worked example:

• Primary school boiler: likelihood 5 × impact 5 = 25; cost €150,000, so €6,000 per risk point
• Town hall lift: 3 × 4 = 12; cost €180,000, so €15,000 per risk point
• Library roof: 4 × 3 = 12; cost €240,000, so €20,000 per risk point
• Depot windows: 2 × 2 = 4; cost €60,000, so €15,000 per risk point
• Funding order on this basis: school boiler, then the lift; the windows cost less per risk point than the roof, but the roof carries three times the risk, so the final call is a judgement the scores inform rather than make
• Any asset without both scores goes on an unscored list for the next condition survey, not to the bottom of the queue

From backlog to a multi-year maintenance plan

A multi-year maintenance plan sets out, per asset and per year, the planned interventions, their cost and the expected condition, usually over five to ten years. In Canada, Ontario's O. Reg. 588/17 requires municipal asset management plans that, from 1 July 2025, include proposed levels of service, lifecycle activities and a financial strategy; a backlog plan is the maintenance part of that strategy.

Worked example. The municipality above decides to clear its €6.4 million backlog in five years, €1.28 million a year. It also needs to stop new backlog forming, and assumes for planning that lifecycle replacement costs 1.5 per cent of replacement value a year: 0.015 × €80 million = €1.2 million. The plan therefore needs €1.28 million + €1.2 million = €2.48 million a year. If the current budget is €1.6 million, the gap is €0.88 million a year, and the plan should show which high- and significant-risk items stay open if the gap is not funded.

Review the plan every year with fresh condition and cost data. Items that fail early move up; items that a cheaper repair has stabilised move down; and the plan's total is updated so that the board sees the real trajectory, not the original estimate.

Monitoring the plan: budget vs actual

A backlog plan fails quietly when reactive repairs consume the planned budget. Split the budget into planned and reactive lines and compare each with actual spending. Worked example for the first half of year one: the budget is €1.24 million, of which €0.40 million is for reactive repairs and €0.84 million for planned backlog work. Actual spending is €0.62 million reactive and €0.43 million planned, a total of €1.05 million.

At headline level the programme looks €0.19 million under budget. Underneath, reactive spending is €0.22 million over and planned work is €0.41 million behind (0.41 − 0.22 = 0.19). The backlog is therefore growing even though the budget looks healthy, and the recovery action is to protect the planned line and to find out why reactive demand is running high.

What to report to a board or council

Boards and councils need a short, stable set of measures, reported in the same format every time. In Ontario, O. Reg. 588/17 requires council to review asset management progress each year on or before 1 July; a regular backlog report makes that review straightforward. A good quarterly pack contains:

• Deferred maintenance cost by risk category, and as a share of replacement value, with the trend
• Operational backlog in crew-weeks by trade, with arrivals and completions
• Open work orders by age bucket and priority, with any high-priority items older than 90 days named
• Planned versus reactive spending against budget
• Progress on the multi-year plan: items completed, deferred and added
• Statutory compliance: certificates current, expired and missing
• Service impact: closures or disruptions caused by estates failures

How Skyline Nexus ERP helps you measure and reduce backlog

In Skyline Nexus ERP, every CMMS work order carries a priority, a status (Open, Assigned, In Progress, On Hold, Completed, Cancelled), the asset and branch, and its labour, parts and external cost, so open work can be listed by age, priority and site in the Work Order Report and exported to Excel or PDF. The Asset Criticality screen plots assets on a likelihood-of-failure by business-impact matrix and lists unscored assets separately, which is the starting point for risk-ranked funding. PPM schedules hold estimated hours and cost, and the PPM Compliance report shows completed work orders against those raised from each schedule. FMS reports also include a Maintenance Backlog report.

On the finance side, Budgets can be set per account, cost centre and fiscal year, and the Budget vs Actual report compares them with the ledger's actual spending, showing total budget, actual spent, variance and an Over Budget, Warning or On Track status; give planned and reactive maintenance their own accounts or cost centres and the two lines can be watched separately. The CMMS Maintenance Costs and Department Costs reports show the cost recorded on each work order. Try the free month with one site's open work orders, or book a demo and we will build your first backlog report with you.