Ask ten developers what their MEP consultant should hand over at Stage 4, and you will get ten different answers. The RIBA Plan of Work gives UK construction a shared map (eight stages from inception to occupation), but building-services scope within it varies enormously, and the gap between what a client assumed and what a consultant priced is where projects lose time and money. For mechanical, electrical and public health design, the substance sits between Stage 3, where the design is spatially coordinated and proven compliant, and Stage 7, when the building is occupied and its systems are tuned. This is what you should expect at each stage.
What does the RIBA Plan of Work mean for MEP design?
It is the framework that defines what is designed, by whom and by when. For building services it marks the point at which systems stop being strategy and become buildable engineering. MEP appointments rarely span all eight stages. In practice they come in three shapes: a Stage 3 package that coordinates the services and proves the scheme can meet Building Regulations; a Stage 4-5 technical-design appointment, sometimes for a single discipline such as mechanical; and a full Stage 4-7 commission running from technical design through construction to handover and aftercare. Whichever shape a project buys, each stage has a defined output, and the output of one stage is the input to the next. Discontinuity between stages, or between consultants, is where design intent gets lost.
Stage 3: spatial coordination and compliance
Stage 3 is where MEP design starts occupying real space. The deliverables are coordinated services layouts with plant rooms sized and positioned, risers located, and horizontal distribution agreed against the structural frame and ceiling zones. Alongside those sits the analytical evidence that the scheme will pass Building Regulations, rather than a promise that it should.
That evidence is produced by modelling, not assertion. Energy performance is tested against Approved Document L through SAP calculations and, where the design warrants it, full dynamic thermal modelling. Overheating in new homes is assessed under Approved Document O, which applies to new residential buildings, alongside the CIBSE TM59 methodology, which simulates internal temperatures room by room across a design summer. The stakes CIBSE cites are stark: projections that mortality arising from overheating could rise from 2,000 deaths a year in 2015 to 7,000 a year by the 2050s. A properly closed Stage 3 ends with an energy statement, an overheating strategy that works without bolted-on cooling, utility applications lodged, plant space that will not need to grow later, and outline specifications a cost consultant can price. The full suite of Approved Documents (F for ventilation, G for water, P for electrical safety, S for electric vehicle charging) is the compliance frame the whole package answers to.
Stage 4: the design a contractor can price and build
Stage 4 turns the coordinated concept into technical design: a federated Revit model, distribution layouts for every level, schematics for each system, plant and equipment schedules carrying selections rather than allowances, and a full specification. The test of a Stage 4 package is blunt: could a competent contractor build it without guessing? Every ambiguity left in the drawings at tender returns during construction as a claim, a substitution or a delay.
The discipline shows most on unconventional systems. At Cyprus Beckton, where 211 apartments are served by an all-electric ambient-loop heat network fed by air source heat pumps, AMF’s Stage 4-5 mechanical scope meant resolving the loop hydraulics, plant selections and apartment heat-pump arrangements fully at Stage 4. A system with no gas fallback leaves no room for on-site improvisation.
What changes for higher-risk buildings under the Building Safety Act?
For higher-risk buildings (broadly, residential buildings above 18 metres or seven storeys), Stage 4 is now a regulatory gateway rather than a milestone. Building control approval must be granted by the Building Safety Regulator before any building work starts, and starting without it is a criminal offence. The consequence for MEP is that the technical design must be genuinely complete at submission: fire-strategy interfaces resolved, service penetrations coordinated, and the design substantiated well enough to survive scrutiny by the regulator’s multi-disciplinary team. The era of finishing the design on site is over for these buildings, and every subsequent change feeds the golden thread of building information. AMF carries these duties on live schemes: Orion Park in West Ealing, 95 all-electric apartments, includes a Higher-Risk Building under the Building Safety Act 2022.
Stage 5: construction, where the design is defended
A consultant who vanishes at tender leaves the client unrepresented for the noisiest half of the project. Stage 5 deliverables are less glamorous but decisive: responses to requests for information; review of contractor technical submittals against the specification, so substitutions are assessed for their knock-on effects rather than nodded through; coordination of specialist-designed packages (BS 9251 sprinklers, BS 8629 evacuation alert, smoke ventilation, BEMS), so that delegating a design never means leaving it unchecked; periodic site inspections; and witnessing of commissioning. This is also where the record of what was actually installed begins, and it is far cheaper to capture it during construction than to reconstruct it at handover.
What should you receive at handover?
At Stage 6, an as-installed record of the building: drawings updated to what was built rather than what was drawn, commissioning certificates for every system, operation and maintenance manuals, the energy performance certificate, and a building user guide written for the people who will run the building. For a higher-risk building, this information passes into the golden thread held by the accountable person, so it must be assembled progressively through Stage 5 rather than improvised in the final month.
Stage 7 is the stage most appointments never reach, and increasingly the most valuable. Low-carbon systems (heat pumps, ambient loops, MVHR) reach their modelled performance only when tuned in occupation. A Stage 7 scope covers seasonal commissioning through the first summer and winter, review of metered energy use against the design model, and adjustment of controls as real occupancy patterns emerge. On a full Stage 4-7 commission, the engineers who made the design decisions are the same people standing behind them in occupation. That is the strongest incentive alignment a client can buy.
The short version
Stage 3 buys certainty of compliance and space, and Stage 4 a design a contractor can price without qualification. Stage 5 buys defence of that design under commercial pressure. What Stages 6 and 7 buy is a building that performs as modelled, with the evidence to prove it. AMF has delivered every shape of these appointments since 2014 (Stage 3 compliance packages, Stage 4-5 single-discipline scopes and full Stage 4-7 MEP commissions), with executive oversight and a named project coordinator on every project. If you are scoping an MEP appointment and want to be precise about what each stage should hand you, talk to us.