# The MEP Coordination Drawing

> An MEP coordination drawing overlays ductwork, pipework, sprinklers, cable containment, lighting and the ceiling grid on one plan and section so that every service has its own agreed space. It is checked at the tightest point on the floor, and it must be signed off before installation, because a clash found above a finished ceiling is fixed by demolition, not by drawing.

## The assumption that costs weeks

The usual belief is that if the air-conditioning designer, the electrical designer
and the fire-protection designer have each produced a correct drawing, the floor
can be built. It cannot, or not reliably. Each of those drawings is drawn against
the architect's plan, and none of them knows what the others have done.

The result is that two trades have quite reasonably been given the same piece of
ceiling void. Nobody is wrong on paper. The conflict only appears when the second
trade arrives with materials and finds the first is already in the way.

The MEP coordination drawing is the document that resolves this **before**
anyone arrives. For a decision-maker, the useful framing is this: it is one of the
cheapest documents in a fit-out, and it protects the most expensive part of the
programme, which is the middle third when several trades are working overhead.

## What is on an MEP coordination drawing

A coordination drawing is not a bigger drawing. It is a layered one, where every
service is drawn to its real size and its real height, and the space each one
occupies is agreed.

| Layer | What it contributes | Why it matters to the others |
| --- | --- | --- |
| Structure | Beam depths, column heads, slab levels, openings | Sets the ceiling void that everything else must fit in |
| Ductwork | Main trunks, branches, dampers, access panels | Largest cross-section, so it claims space first |
| Pipework | Chilled water, drain slopes, sprinkler mains and branches | Sloping lines cannot simply move up or down |
| Cable containment | Trays, trunking, conduit routes | Needs clear access and separation from other services |
| Lighting and devices | Fittings, detectors, diffusers, speakers | Fixed to the ceiling grid, so it dictates positions |
| Ceiling | Grid layout, tile size, access hatches | The finished surface that all the above must sit behind |

Two things separate a real coordination drawing from a stack of drawings.

**First, heights are shown, not just plan positions.** Two services can share a
plan location perfectly well if one is above the other. Without levels marked, a
plan cannot say whether they fit. That is why sections matter as much as plans.

**Second, clearances are drawn in.** A duct needs its insulation, a valve needs
room to operate, a damper needs an access panel and a light fitting needs
clearance above it. A drawing that shows the bare service size passes routes that
cannot actually be installed or maintained.

## Checked at the tightest point

The most common way to get coordination wrong is to check a typical bay.

A typical bay tells you very little. Most of the floor usually has room to spare.
The design succeeds or fails at the few places where everything converges: where
a beam drops, where the main duct trunk meets a sprinkler main, where cable tray
crosses a corridor, or where a service passes a structural element.

So the drawing needs **sections cut through the worst locations**, not a
representative one. If the services fit there, the rest of the floor is
unlikely to be a problem. If they do not, that is precisely what you needed to
know before ordering.

This is also where the available ceiling depth becomes a real number rather than
an assumption. The relationship between finished ceiling height, void depth and
what must fit inside it is covered under [plenum depth](/glossary/plenum-depth),
and it is often the first thing a coordination drawing reveals is tighter than
the design intent.

A related location is the slab edge and other penetrations, where services pass
through fire-rated construction. Those points need the sealing arrangement
resolved as part of the drawing rather than left to be improvised, which is what
[slab edge firestop](/glossary/slab-edge-firestop) describes.

## Who produces it, and why ownership matters

The drawing is normally produced by the contractor or a specialist coordinator,
working from each trade's design, and reviewed by the trade designers and the
project's consultants.

What matters is not who holds the pen. It is that **one named party owns the
combination**, has authority to require a trade to move, and signs the drawing off
only when every trade has accepted it.

This is one place where the contract structure shows up. Where a single contractor
is responsible for all the services, one party can resolve conflicts between
trades. Where each trade is contracted separately, the conflict crosses a
commercial boundary, and someone has to decide who moves and who pays. That
difference is discussed in
[turnkey vs item-rate fit-out contracts](/compare/turnkey-vs-item-rate-fit-out-contract).

## Design coordination and site coordination are different jobs

They are often confused, and they cost very different amounts.

| | Design coordination | Site coordination |
| --- | --- | --- |
| When | Before ordering and installation | During installation |
| Where the fix happens | On the drawing | In the ceiling void |
| Typical cost | Drawing time | Rework, idle trades, replacement material |
| Who is affected | Designers and coordinator | Every trade waiting behind |
| Effect on programme | Usually none | Directly on the critical path |

Site coordination is never fully avoidable. Structure is not built exactly to
drawing, existing services turn up where they were not shown, and installers work
to tolerances. But it should be dealing with **small variances**, not whole
clashes. When site coordination is doing the work of design coordination, the
programme is already in trouble.

## What a clash costs once the ceiling is up

A clash found on a drawing costs an edit. A clash found in the void costs more
in several ways at once.

- **Demolition.** Something already fixed must be removed. A duct or sprinkler
  main that has been installed and tested is not moved casually.
- **Re-testing.** Pipework that is altered may need to be tested again, and the
  sequence of tests then delays the ceiling closing.
- **Waiting trades.** Everyone behind the affected trade stops. This is the part
  that turns a local problem into a programme problem.
- **Replacement material.** A duct fabricated to a length and route may need to
  be remade, not adjusted.
- **Knock-on to other trades.** Moving one service often pushes a neighbour,
  which was itself coordinated.

None of these is dramatic on its own. The cost is that they are discovered when
several trades are mobilised, and it is the idle time of that whole group that
hurts. The specific cost depends entirely on the project, which is why it is
better described as a sequence of consequences than as a number.

## The ceiling void sequence the drawing must respect

The coordination drawing is only useful if it matches the order of work. Typically
the void is filled in a sequence: structure and any strengthening first, then main
ductwork, then sprinkler and other pipework, then cable containment, then lighting
and devices, and finally the ceiling.

The drawing should reflect this. A service that must be installed early is
given the space it needs first, and services that follow are routed around it.
Drawn the other way, the last trade in finds the void already full.

Building services provisions are set out in **NBC 2016, Part 8**, and the
fire-protection layout is governed by the fire and life safety provisions in
**NBC 2016, Part 4**. Electrical installation practice is covered by **IS 732**.
Which provisions apply to your building and how they affect routing must be
confirmed by the project's engineers.

## Common mistakes

**Treating the coordination drawing as a deliverable, not a decision.** It is
produced, filed and never reviewed by the trades. The trades then build to their
own drawings.

**Coordinating only in plan.** Without levels and sections, two services drawn
in the same place are flagged as a clash when they are not, and real clashes at
different levels are missed.

**Leaving out the ceiling.** The grid, tile module and light positions are what
tell you where devices must sit. A coordination drawing without the ceiling
leaves the visible result to chance.

**Freezing it too late.** If ductwork has been fabricated before the drawing
is agreed, the drawing can only record the problem.

**Ignoring access.** Valves, dampers and junction boxes that have been
coordinated into the void but are behind a fixed ceiling cannot be maintained.
Access panels belong on the drawing.

**Not marking the as-installed position.** The void should be photographed and
compared with the drawing before the ceiling closes. It is the last cheap chance
to find a difference.

## What to ask

- Who owns the coordination, and do they have authority to instruct a trade to
  move?
- Are there sections through the tightest locations, with levels shown?
- Does the drawing include the ceiling grid, light positions and access panels?
- Has each trade accepted it in writing, not simply received it?
- When does it have to be signed off, relative to ordering the long-lead items?
- How will the installed position be checked before the ceiling is closed?

A contractor who answers all six has a process. One who says the trades will
sort it out on site has a risk.

## Standards referenced

Building services provisions in **NBC 2016, Part 8**; fire and life safety
provisions in **NBC 2016, Part 4**; electrical wiring installations in **IS 732**.
The routing, clearances, separation and fire-related provisions that apply to a
specific building must be confirmed by the project's engineers and consultants
and, where relevant, the authority having jurisdiction.

## Frequently asked questions

### Is an MEP coordination drawing the same as the individual MEP drawings?

No. Each trade's own drawing shows only that trade, usually against the architect's plan. The coordination drawing overlays all of them, plus the ceiling and structure, on the same sheet. Every individual drawing can be correct and the combined result can still be impossible to build, which is the problem the coordination drawing exists to catch.

### Who produces the coordination drawing?

Usually the contractor or a specialist coordinator, working from each trade's design, with the trade designers and the consultants reviewing it. The important point is that one party is named as responsible for combining them and for chasing each trade to resolve its clashes. If no one owns it, it tends to be done informally on site, which is the expensive version.

### When does it need to be finished?

Before installation starts, and before any long-lead item is fixed in a position that depends on it. It also has to be signed off by the trades, not just issued to them. A drawing that exists but that a trade has not accepted resolves nothing, because that trade will install to its own drawing.

### What is the difference between design coordination and site coordination?

Design coordination resolves the conflicts on paper, before anything is ordered or installed, and costs drawing time. Site coordination resolves them after materials are on the floor, and costs rework, waiting trades and sometimes replacement material. Site coordination is still necessary, because buildings differ from drawings, but it should be dealing with small variances rather than whole clashes.

### Why is it checked at the tightest point rather than a typical one?

Because the tightest point is where the services cannot all fit, and that is the point that decides whether the design works. A typical bay proves nothing. Beams, column heads, the main duct trunk, a sprinkler main and a cable tray crossing in one location are what typically cause trouble, so the drawing needs sections cut through exactly those places.

### Does a coordination drawing remove the need for on-site checks?

No. It reduces the number and size of the problems but does not remove them, because structure, existing services and workmanship all vary from the drawing. Good practice is to mark up the installed position against the coordination drawing before the ceiling is closed, so that what is behind the tiles is a known quantity.

## Sources

- [NBC 2016, Part 8](https://www.bis.gov.in/standards/national-building-code/?lang=en) — Building services
- [NBC 2016, Part 4](https://www.bis.gov.in/standards/national-building-code/?lang=en) — Fire and life safety
- [IS 732](https://standards.bis.gov.in/website/published-standards/department-wise) — Code of practice for electrical wiring installations

---

Source: https://hagerstone.com/blog/mep-coordination-drawing-what-it-shows