MEP coordination is the process of establishing that the ductwork, pipework, conduit, sprinklers, cable tray and structure can all occupy the same space above the ceiling. On most projects it is completed after the price is fixed, which means the answer to whether everything fits arrives after somebody has already guaranteed it does.
Why the drawings do not answer the question
Design drawings show each system separately. The mechanical drawings show ducts, the plumbing drawings show pipes, the electrical drawings show conduit and tray, the fire protection drawings show sprinkler mains.
Each is drawn to be correct for its own system. None of them is drawn to prove that all of them fit together in the actual space available.
That proof comes from coordination, which combines the systems in a single model and resolves the conflicts. It is done by the trades, after award, working from shop drawings rather than from design drawings.
So the sequence on a conventional project is: design, price, guarantee, award, then find out whether it fits.
Most of the time the answer is yes with modest adjustment, absorbed in the trade prices. The exceptions are expensive, and they cluster in predictable places: tight plenum depths, complex mechanical rooms, corridors carrying every system at once, and any building where the floor to floor height was minimized to gain a story.
Where MEP coordination fails, and what it costs
Five conditions produce most of the problems and all five are visible before signature.
Thin plenum. Where the space between the structure and the ceiling is under about eighteen inches on a commercial building, every system is competing and the resolution is usually structural or is a lower ceiling.
Large ducts crossing beams. Penetrations require structural approval, and beam penetration limits are frequently discovered after the duct routing is set.
Corridors as the common route. Everything runs in the corridor, and corridors are also where ceiling heights are most constrained by door heights and code.
Sprinkler mains late in the sequence. Fire protection is often designed last and coordinated last, which means it routes around everything else and needs the most drops and offsets.
Structural transfer zones. Where a podium transfers loads, the structure is deep and the services have nowhere to go, which is the condition described in the transfer level.
The cost of resolution is rarely the fittings. It is the ceiling heights, the structural modifications and the schedule consequence of resequencing.
Clash detection is not the same thing
Running a clash report identifies geometric conflicts. It does not resolve them, it does not say who pays, and it does not establish whether the resolution is buildable or maintainable.
A model with nine hundred clashes reported and no resolution process is a document describing a problem. The commercial question is which of those nine hundred require a change to the design rather than a change to the routing, because the first category is a cost and the second is coordination the trades carry.
The distinction between the geometric exercise and the commercial one is the subject of clash detection and constructability review, and it matters here because owners frequently take comfort from the existence of a model.
The useful questions about a coordination process are about governance rather than software. Who chairs it. Who resolves a conflict when two trades disagree. Who decides when the resolution requires a design change. And who pays for that change.
Contracts that answer those four make coordination a process. Contracts that are silent make it a negotiation, repeated several hundred times.
A worked example
Illustrative figures. Not taken from any client project and not a quotation.
A seven story office building with 13 foot 6 inch floor to floor and a 9 foot ceiling, leaving roughly 20 inches of plenum after structure.
The guaranteed maximum price is agreed at eighty five percent documents. Coordination begins after the mechanical award in month five.
By month eight the coordinated model shows that the primary duct runs cannot achieve the required routing within the plenum at 31 locations, mostly where the corridor crosses beam lines.
Resolution: 19 locations are resolved by duct reshaping and additional fittings, absorbed by the trade. 8 require structural penetrations requiring engineering review and reinforcement, $310,000. 4 require the ceiling to drop by six inches in specific zones, which changes the lighting layout, the sprinkler layout and the door schedule in those areas, $520,000.
The redesign and coordination effort, the associated delay to the interiors sequence, and the resequencing add a further $470,000.
Total $1.3 million. A pre signature review of the three tightest sections against the plenum depth, taking about two days, identifies the same 31 locations while the price is still being negotiated.
What can be checked before the price is fixed
A full coordination cannot be run before award. A useful approximation can, and it takes days rather than months.
Take three or four representative sections: a typical corridor, the tightest floor, the area below any transfer structure, and one mechanical room.
Add up the depths. Structure, the largest duct in that zone, the sprinkler main with its required clearance, the largest pipe, the cable tray, and the clearances each requires. Compare to the available space.
Where the total exceeds the space, the project has a coordination cost and it is quantifiable at that point rather than in month eight.
This is arithmetic rather than modeling, it requires no software, and it finds the conditions that matter because those conditions are about depth rather than about individual clashes.
The same exercise also tells the owner whether the contractor coordination allowance, where one exists, bears any relationship to the building.
One further check is worth the time on any building where the floor to floor height was set to gain a story. Ask what the plenum depth was at concept and what it is now. Where it has been reduced during design to preserve ceiling heights or to hold the building height, the coordination cost was created by a decision somebody took, and it is worth knowing who took it and when.
That is also the one condition where the answer may be to change the design rather than to price the coordination, and it is only available before the price is fixed.
Who pays, and what the contract should say
Coordination itself is a contractor obligation on almost every form. What is not settled is what happens when coordination reveals that the design does not fit.
Three positions are possible and the contract should pick one.
The contractor carries it, on the basis that it guaranteed a price for a building shown in the documents. Defensible where the documents were complete and the contractor had the chance to assess them.
The owner carries it, as a design development cost, on the basis that a design that does not fit is a design problem. Defensible where the price was agreed on an incomplete set.
It is shared, with a threshold: the contractor absorbs the first stated sum, the owner carries the balance up to a cap. This is the most workable position on a project priced at eighty five percent documents, which describes most guaranteed maximum prices.
Whichever is chosen, saying so at signature is worth more than the allocation itself, because the alternative is discovering in month eight that both parties assumed the other one carried it.
What we do
We run the section arithmetic on the tightest conditions before signature, quantify what the coordination is likely to cost and where, and settle who carries a design that does not fit. Then we read the coordination governance: who chairs it, who resolves conflicts and who decides when a change is a design change. That work is part of the constructability and interface review. Where an owner’s representative carries this reading, support for owner’s representatives does the reading while they keep the relationship.
Questions people ask
Should coordination be complete before the price is agreed?
Ideally yes, and it almost never is, because coordination is done by trades who have not yet been awarded. What is achievable is a check on the tightest conditions before signature, which finds the expensive problems without requiring the full process to have run.
Does a detailed model remove the risk?
It removes the geometric surprises and that is genuinely valuable. It does not remove the commercial question, which is who pays when the resolution requires a design change rather than a routing change. A model with no agreement about that produces the same arguments with better pictures.
Which trade should lead coordination?
Usually mechanical, because ductwork is the least flexible system and the largest. What matters more is that somebody has authority to decide when two trades disagree, and that the decision maker is named in the contract rather than emerging by default six months in.
This is general information about construction contracts and is not legal advice.