On a London residential development, the mechanical, electrical and public health (MEP) design carries more consequence than its fee line suggests. It underpins the energy strategy on which planning consent rests, fixes the riser and plant space that shapes saleable area, and produces the compliance evidence that building control (and, on taller buildings, the Building Safety Regulator) must approve before work can start. Appointing the consultant who produces that design is a commercial decision, not a procurement formality. This guide sets out when to appoint, what to look for, the questions worth asking, the warning signs, and how scope and RIBA stages actually drive fees.
When should you appoint an MEP design consultant?
Appoint at RIBA Stage 2, concept design, and no later than the start of Stage 3. That is the window in which the decisions an MEP engineer most influences are still cheap to change: communal heat network or individual heat pumps, riser positions, rooftop or basement plant, electrical load and any substation requirement.
Two regulatory realities reinforce the timing. First, overheating compliance under Approved Document O, which applies to new residential buildings, is largely determined by the architecture: glazing ratios, orientation, the availability of cross-ventilation. If dynamic thermal modelling arrives after the planning scheme is fixed, the mitigation options left are the expensive ones. Second, on higher-risk buildings (those at least 18 metres or seven storeys tall with two or more residential units), building control approval from the Building Safety Regulator must be granted before construction starts, and the client is responsible for making sure it is. That regime rewards a Stage 4 design that is genuinely complete, and punishes one that is not, in programme.
What should you look for in an MEP consultant?
Evidence, in three forms: delivered projects of your building type and scale, in-house analytical capability, and named senior engineers who will stay on the job.
Comparable projects matter because London residential has converged on a specific technical territory: all-electric heat, air source heat pumps, ambient loops, MVHR, heat networks. A practice that has delivered it recently will design it faster and defend it better in planning and technical review. At Cyprus Beckton, for instance, AMF carried the Stage 4-5 mechanical design for 211 apartments served by an all-electric ambient-loop air source heat pump network; that is the kind of directly relevant, recently delivered work a shortlist conversation should surface.
In-house capability means the consultant runs its own dynamic thermal modelling to CIBSE TM59, the industry methodology for assessing overheating risk in dwellings, whose 2026 edition tests homes against 2050s weather data. It also means running its own energy calculations against Approved Document L rather than buying in results it cannot interrogate. And production capability means native Revit and BIM coordination, because on a tightly coordinated residential frame, services drawn outside the model are services clashed on site.
Questions to ask before you appoint
Six questions do most of the work at interview:
- Who, by name, will run this job day to day, and what else is that engineer running?
- Show us the TM59 outputs and Part L calculations from your most recent comparable scheme. Who produced them?
- What, precisely, is in your Stage 4 deliverable set (schematics, schedules, specifications, coordinated models), and can we see an example?
- Where does your design responsibility end and contractor design begin, and where is that boundary written down?
- If our scheme is a higher-risk building, how does your design programme align with building control approval before start on site?
- What is excluded: surveys, vertical transportation, BEMS, smoke ventilation, utility applications, site inspections?
A strong practice answers all six specifically. A weak one answers with adjectives.
How do scope and RIBA stages drive fees?
MEP fees are a function of three variables: which RIBA stages the appointment covers, how deep the deliverables go within each stage, and how much design responsibility the consultant retains. Two quotes for “Stage 3-4 MEP design” can describe very different services, which is why fee comparisons made on headline numbers alone routinely mislead.
Stage 3 produces a spatially coordinated design that fixes strategy and space. Stage 4 is where cost concentrates, because the construction-level detail of coordinated models, full specifications and equipment schedules takes engineering hours to produce. It is also where cost is recovered: the more complete the Stage 4 information, the less risk contractors price into their tenders and the fewer variations follow. Appointments that stop at “design intent” and pass the detail to contractor design portions shift that cost; they do not remove it. Stages 5-7 cover site inspections, commissioning witnessing and record-information review. These are the lines most often trimmed from a fee and most often regretted at handover.
The practical discipline is to procure against a deliverables schedule, not a stage label: ask every bidder to price the same list, then interrogate any fee that sits far below the rest, because the difference is nearly always scope you will end up buying twice.
Red flags
Treat the following as warnings worth acting on:
- No named engineers: a practice selling capacity, not people.
- A portfolio in a different building type, offered as though it transfers.
- Thermal and energy modelling outsourced with no in-house scrutiny of the results.
- A Stage 4 offer described as “design intent” with no deliverables schedule attached.
- Silence on the Building Safety Act on a scheme over 18 metres.
- No exclusions list at all, which means the exclusions will be discovered later, as disputes.
- A fee dramatically below the field with no scope difference to explain it.
None of these is fatal on its own; two or more together usually are.
Talk to us early
AMF MEP has designed building services for residential schemes across London since 2014, with executive oversight and a named project coordinator on every appointment. That work includes Passivhaus homes at Custom House in Newham and Orion Park in West Ealing, where 95 all-electric apartments include a Higher-Risk Building under the Building Safety Act 2022. If you are approaching Stage 2 or 3 and weighing an MEP appointment, start the conversation now: it costs nothing, and the timing is worth a great deal.