What sits under each letter
| Discipline | Scope | Typical share of a fit-out |
|---|---|---|
| Mechanical | HVAC, ducting, ventilation, extract, BMS | 15–22% |
| Electrical | LV distribution, power, lighting, data, fire alarm | 12–18% |
| Plumbing | Water supply, drainage, pantries, washrooms | 3–7% |
| Fire protection | Sprinklers, detection, suppression | 3–6% |
First fix and second fix
First fix is everything buried before surfaces close: conduits, cabling, pipework, duct runs, drainage falls. Second fix is everything visible afterwards: switches, sockets, light fittings, taps, grilles, sanitaryware. The rule that governs a project is that no ceiling or wall closes until the first fix behind it has been tested and photographed. Reopening a false ceiling to chase a fault costs ten times what testing it cost.
Where residential MEP goes wrong
- Socket positions decided after the furniture layout changed, leaving points behind a wardrobe.
- AC drain lines run with insufficient fall, which produces a wet wall in the second monsoon.
- No isolation valve inside a kitchen cabinet, so the whole flat's water must be shut off to change a tap.
- Data and TV cabling omitted because everything is wireless — until a TV needs an HDMI run through a stone panel.
- A load calculation that never happened, and a DB that trips when the AC and the oven run together.
Load is the calculation most often skipped in a flat. A 2BHK with two air conditioners, a geyser, an oven and a microwave draws 7–9 kW at peak, against a sanctioned load that may be 3–5 kW. Establish the sanctioned figure before adding appliances, because raising it is a utility application, not an electrician's job.
Getting it right
MEP is decided on drawings, not on site. An electrical layout marking every point at its height, a plumbing layout with pipe routes and falls, and a reflected ceiling plan coordinating lights, diffusers, sprinklers and speakers — those three sheets prevent almost every services problem that shows up later. See working drawings, electrical planning for interiors and office fit-out.
Frequently asked questions
What is included in MEP?+
Mechanical — HVAC, ventilation and extraction. Electrical — distribution, power, lighting, data and fire alarm. Plumbing — water supply, drainage and sanitary. Fire protection is often counted as a fourth discipline alongside them.
How much of an interior budget is MEP?+
30–45% of a commercial fit-out, and 12–20% of a residential project where the base services usually already exist. In a flat, the MEP share rises sharply if you are relocating a kitchen or adding a bathroom.
Can MEP be changed after the ceiling is closed?+
Only by opening it. That means cutting gypsum, making good, repainting and losing several days. It is the single strongest argument for testing and photographing every first fix before any surface closes.
Who coordinates MEP in a residential project?+
In a turnkey contract, the contractor. In a design-only arrangement it falls to you unless you appoint someone. Uncoordinated services is the most common reason a flat's ceiling ends up 100 mm lower than it needed to be.