Almost every data center project needs both permanent staff and contractors, so the decision that matters is which roles go which way. The question we ask about each role is whether the work, and what the person learns while doing it, needs to stay with you after the project ends. If it does, hire permanently. If the role ends at handover, contract it.
That rule settles most roles on a build. The rest depend on what kind of business you are, on what each option costs in the UK today, and on two recent changes in UK law. Since April 2026 you, or your agency, can be liable for a contractor's unpaid tax, and from January 2027 a permanent employee can claim unfair dismissal after six months' service. We cover each of these below for the developers, operators, main contractors, MEP subcontractors and commissioning firms that staff data center builds.
How the workforce on a data center project rises and falls
A data center employs far more people while it is being built than once it is running. QTS expects its campus at Cambois in Northumberland to create about 1,200 construction jobs and 400 operational ones. Even the construction workforce changes as the build goes on. Civil and structural trades come first, electrical and mechanical installation follows, and a commissioning team then tests every system before the building is handed over. Commissioning is also when the plant passes from the people who installed it to the people who will run it, and the hardest staffing decisions on a project sit at that point.
A permanent workforce sized for the construction peak would have little to do for most of the programme, and one sized for operations could never build the site. That is why projects mix the two. People are also hard to find on both sides of the split. In Turner & Townsend's Data Center Construction Cost Index 2026-27, 81% of respondents said skilled labour in their region was constrained, and MEP trades were the most sought after. In that market the best contractors are booked well ahead, just as the best permanent candidates are, so whichever route you choose for a role, start early. We wrote about matching hiring to faster build programmes in our article on workforce mobilisation.
Which data center roles suit contract and which suit permanent hiring
On most UK and European projects where the client is building a single site, the split we see working looks like this.
The operations manager, critical facilities engineers and shift technicians should be permanent, because they will run the building for years and need to learn it while it is being commissioned. The developer's or operator's site director usually should be too, since their decisions affect the site long after the build is finished. The exception is a client with no further sites planned, where a contract director can see the project through and leave.
Client-side project and package managers suit contract, because their role ends at handover. So do commissioning managers and engineers, whose numbers peak through the later levels of testing and then fall to almost nothing, which is why many clients take them through a commissioning firm. QA/QC and HSE staff are also best on contract, so that their numbers can follow the amount of work on site.
BMS and controls engineers fall on both sides. The engineers who install and commission the system can be contractors, but someone on the operator's side has to own it once the installer has gone, and that person should be a permanent hire who joined in time to watch it being commissioned.
The split changes for a campus built in phases. A site with several halls going up one after another is really a series of projects, and the people who lead each phase take what they learned into the next one. For a phased campus, the programme director, the commissioning lead and the senior project managers are usually worth hiring permanently, even though on a single building they would be contract roles.
Why operations staff should be permanent and on site before commissioning
The case for a permanent operations team is about timing as well as contract type. In the Uptime Institute's 2025 outage analysis, 85% of outages caused by human error came from staff failing to follow procedures or from flaws in the procedures themselves. A new data center's operating procedures are written and tested during commissioning. If your permanent team arrives after the commissioning contractors have gone, it inherits procedures it did not help write, for plant it has never seen tested.
Hire the operations manager and the senior critical facilities engineers before commissioning starts, and have them attend the later levels of testing, including the integrated systems test. BSRIA's Soft Landings framework applies a similar idea to buildings in general, with a pre-handover phase that prepares the people who will run the building and a period of aftercare once they have taken it over. Hiring early costs a few months of salary before the site earns any revenue. Skipping it costs more, because you either keep commissioning contractors on to train a new team or open the building with staff who learned it from a handover file.
Once you have an operations team, keeping it is the harder part. In the Uptime Institute's 2026 Global Data Center Survey, 53% of operators said they had difficulty finding qualified candidates, and 28% said competitors had hired staff away from them. An operations team made up of contractors faces that risk each time a contract comes up for renewal. Permanent staff get approached too, but you can offer them pay reviews and a route to promotion, which a contractor on a fixed day rate does not have.
How the answer changes for firms that build data centers for a living
Main contractors, MEP subcontractors and commissioning firms face a different problem. Each project ends, but the business moves on to the next one. The people who take your methods, your safety standards and your client relationships from one site to the next should be permanent. These are your project and construction directors, senior package managers, commissioning leads and the engineers you put in front of a client at bid stage. Contractors then cover the peaks, the specialist gaps and the sites too far from home for your permanent people.
For these firms, the main risk to the permanent team comes at the end of each job, when a competitor with a newly awarded project can offer more. Turner & Townsend's Global Construction Market Intelligence report for 2026 found that in more than 70% of the 112 markets it analysed, contractor capacity for data centers was tightening or stretched, which made data centers the most constrained sector it covered. In a market like that, your best people get the most approaches in the last weeks of a project. You keep more of them if you confirm their next site before the current one finishes than if you make counter-offers after they have been approached.
What a contractor costs compared with a permanent hire in the UK
A contractor costs more per day but can cost less in total when the work is short. IT Jobs Watch's figures for UK roles that cite data centers, in the six months to 3 November 2026, give a median permanent salary of £70,000 and a median contract rate of £525 a day. Both are based on advertised roles, so use them as a guide to the gap and not as a quote.
A permanent engineer on £70,000 costs about £81,000 a year once you add employer National Insurance, which has been 15% on earnings above £5,000 since April 2025, and the minimum workplace pension contribution. That is before any bonus, benefits, equipment or training, and before the recruitment fee if an agency fills the role. A contractor on £525 a day for 220 working days costs about £115,500. That figure is the rate the contractor receives, and an agency adds its margin on top.
Taking the fee and the margin into account, the contractor becomes the more expensive option after roughly six to nine months of continuous work. For a shorter need, contract is cheaper, and you also avoid carrying a permanent employee with nothing to do once the project ends. For a longer need, a permanent hire is cheaper only if you have work for that person after the project. That condition decides most cases, and it explains why a main contractor with a pipeline of work and a developer with one site can reach opposite answers for the same role.
How quickly each route can put someone on site
Contractors usually arrive sooner. For commissioning, project management, QA and HSE roles we can typically present screened contractors within 48 to 72 hours of a brief, because many are finishing one project and already looking for the next. A permanent search takes longer. We usually deliver a shortlist within one to two weeks, interviews and an offer take a further three to six weeks, and an engineer who is employed elsewhere then has to work their notice period, which at senior level is often one to three months.
In practice, if commissioning starts in four months and you want a permanent operations manager on site for it, start the search now. If the search starts later than that, plan for a contractor to cover the gap until the permanent hire arrives.
UK employment and tax rules that now affect the choice
The first change affects permanent hires. From 1 January 2027, under the Employment Rights Act 2025, employees can claim unfair dismissal after six months' service instead of two years, and the cap on the compensatory award is removed. The change applies to dismissals from that date, so it covers people you have already hired. As a result, a permanent employee hired for one project and let go when it finishes can bring an unfair dismissal claim once they pass six months. If a role will end with the project, make that clear in the terms from the start, either through a fixed-term contract or by engaging a contractor, and take employment advice on how the arrangement will end.
The second change affects contractors. Since 6 April 2026, when a contractor is paid through an umbrella company, the agency that contracts with you has been responsible for making sure PAYE is operated correctly. If you engage the umbrella company directly, without an agency, that responsibility is yours, and HMRC can recover unpaid tax and National Insurance from whoever holds it. This applies alongside the off-payroll working rules, known as IR35, under which medium and large clients decide each contractor's employment status, issue a status determination statement and become liable for the tax if they fail to take reasonable care. Using contractors therefore means using a supply chain you can check. Ask your agency which umbrella companies it works with and how it audits them, and keep the status determination for every contractor working outside IR35 on file.
Moving a contractor into a permanent role
Some contractors turn out to be worth keeping. A commissioning engineer who has tested every system in your building can be the strongest candidate for a senior operations role there, and some operators bring contractors onto the permanent team for that reason. If you think you might want to, read the transfer clause in your agency's terms before the contractor starts. UK regulations limit when an employment business can charge a transfer fee, and a fee is only enforceable if the agency also offers you the option of a longer period of hire instead. The terms you agree at the start therefore decide what a conversion costs later.
How Clear resources data center projects
Clear runs permanent placement and contract and freelance recruitment as separate practices, with the same specialist consultants behind both, so one brief can cover the permanent and contract sides of a project. Our design and commissioning and technical operations pages cover the roles discussed here in more detail, and our article on the UK skills shortage sets out current pay by discipline. If you are planning the resourcing for a build, talk to our team.
Permanent vs contract recruitment FAQs
Is it cheaper to use contractors or permanent staff on a data center project?
For short needs, contractors are usually cheaper. Using UK median figures for data center roles, a contractor at £525 a day becomes more expensive than a £70,000 permanent hire after roughly six to nine months of continuous work, and the exact point depends on the recruitment fee and the agency's margin. A permanent hire is cheaper beyond that only if there is work for the person after the project ends.
Which data center roles should be permanent?
The operations manager, critical facilities engineers and shift technicians who will run the building should be permanent, along with anyone whose decisions outlast the build. Main contractors and commissioning firms should also keep their project leaders and senior engineers permanent, because those people carry the firm's capability from one project to the next.
When should you hire the operations team for a new data center?
Hire them before commissioning starts. The operating procedures for a new site are written and tested during commissioning, and the Uptime Institute found that 85% of outages caused by human error came from procedures that were not followed or were flawed. An operations team that attends the later levels of testing knows the plant and the procedures before it takes over.
Who is liable for a contractor's tax in the UK?
Under the off-payroll working rules (IR35), medium and large clients decide a contractor's employment status and can become liable if they fail to take reasonable care. Since 6 April 2026, where a contractor is paid through an umbrella company, the agency is responsible for making sure PAYE is operated correctly, or the end client if there is no agency.
What changes for permanent hires in the UK in January 2027?
From 1 January 2027, the qualifying period for unfair dismissal falls from two years to six months, and the cap on the compensatory award is removed. A permanent employee hired for a single project can bring a claim once they pass six months' service, so set up roles that will end with the project as fixed-term or contract roles from the start, and take employment advice on how they will end.
Can you convert a data center contractor to a permanent employee?
Yes. A commissioning contractor who tested the building can be one of the strongest candidates for a permanent operations role there. Check the transfer clause in your agency's terms before the contractor starts, because UK regulations limit when a transfer fee can be charged.
Sources referenced in this article
- Cambois data center campus, QTS
- Data Center Construction Cost Index 2026-27, Turner & Townsend, 22 October 2026
- Global Construction Market Intelligence report 2026, Turner & Townsend, 8 July 2026
- Annual Outage Analysis 2025, Uptime Institute, 6 May 2025
- Global Data Center Survey 2026, Uptime Institute
- Soft Landings Framework 2018 (BG 54/2018), BSRIA
- Permanent salaries and contract rates for UK data center roles, IT Jobs Watch, six months to 3 November 2026
- Rates and thresholds for employers 2026 to 2027, HMRC
- Employment Rights Act timeline update, Department for Business and Trade, updated 22 October 2026
- PAYE rules for labour supply chains that include umbrella companies, HMRC, updated 19 June 2026
- Off-payroll working for clients, HMRC
- Conduct of Employment Agencies and Employment Businesses Regulations 2003, regulation 10
