MEP coordination is where mechanical, electrical and plumbing services stop being three separate designs and become one buildable installation. Done properly it is invisible. Done poorly it shows up as a duct through a beam, a cable tray in a doorway, or a hydraulic run that cannot be maintained once the ceiling closes.
What MEP coordination drawings actually are
They are drawings that show every service in the same space at the same time, resolved against each other and against structure. Not three service drawings issued in parallel — one coordinated model and drawing set where every clash has been found and settled before anything is fabricated.
Typical contents:
- Composite plans showing all services in a given zone
- Sections through congested areas — risers, plant rooms, corridor ceilings
- Levels and setting-out for each service
- Penetration schedules for structural coordination
- Clash reports with resolution status
- Fabrication-ready spool and containment drawings where required
Where clashes actually come from
Very few clashes are careless. Most come from a small number of predictable sources:
- Design sequence. Structure is fixed first, mechanical claims the ceiling void next, and electrical and hydraulic take what is left. The last discipline in inherits the problem.
- Zoning assumptions. Each discipline assumes a generous allowance in the void. Added together the allowances exceed the void.
- Maintenance access. A run can be geometrically clear and still be wrong because a valve cannot be reached or a filter cannot be withdrawn.
- Structural penetrations. Services routed before penetration positions are agreed, then penetrations proposed where the engineer will not permit them.
- Level changes. Falls on drainage are non-negotiable and everything else has to accommodate them. Coordinating gravity services last is a common and expensive mistake.
How the process runs
Model federation
Discipline models are brought into a common coordinate system with a shared origin. Getting the origin right at the start prevents a whole category of phantom clashes.
Clash detection
Automated detection produces a raw clash list, which is always larger than the real problem — insulation overlaps, tolerance touches and duplicate instances inflate it. The list is triaged into hard clashes, clearance issues and noise.
Resolution
Each hard clash is assigned and resolved by moving a service, changing a route, adjusting a level or agreeing a penetration. Resolution is recorded against the clash so there is an audit trail.
Re-run and sign-off
Detection is re-run after changes, because resolving one clash frequently creates another in a congested zone. Sign-off happens per zone, not per discipline.
Drawing issue
Coordinated composite drawings and sections are issued for construction, with penetration schedules released to the structural engineer.
Priority order that usually works
Where a void is genuinely tight, coordinating in this order resolves the most conflicts with the least rework:
- Gravity drainage — fixed falls, no flexibility
- Large ductwork — bulky and hard to reroute
- Sprinkler mains — regulated coverage geometry
- Pressurised hydraulic services
- Cable tray and containment
- Small-bore and flexible services
Australian context
Coordination drawings are produced against the National Construction Code and the relevant Australian Standards for each service, plus the project’s own drawing conventions. Fire separation and penetration sealing requirements frequently dictate routing more than spatial congestion does, so they belong in the coordination process rather than as a later check.
Common questions
Is a clash-free model the same as a coordinated one?
No. A model can be clash-free and still be unbuildable and unmaintainable. Clearance, access, installation sequence and support all sit outside automated clash detection.
When should coordination start?
As soon as discipline designs are advanced enough to have real geometry. Starting after documentation is complete converts coordination into rework.
Do you work from our models or produce them?
Either. Optimal Drafting can federate and coordinate existing discipline models, or produce the services models from design documentation and coordinate from there.
Getting a coordination scope
Send through the discipline models or documentation you have, along with the zones that concern you most. We will come back with a scope covering federation, clash resolution and drawing issue, and a quote against it.
Reference: fire separation and service penetration requirements are set by the National Construction Code, published by the Australian Building Codes Board.
Service page: MEP drafting services in Australia — scope, deliverables, LOD and turnaround.