What Is a Coordination Drawing?

Corridors, shafts, equipment rooms, and anywhere a reflected ceiling plan shows a tight plenum are the usual zones. The specification should name them. If it does not, the superintendent still needs the overlay before hangers go in, because the first trade to hang pipe wins the space by default.

A coordination drawing is a construction-phase document. Asking the design team to produce it as a CD deliverable mixes two scopes, unless the contract expressly moved that work to the architect or a VDC consultant.

Background grids, elevations of each main, hanger zones, access panels, and the ceiling. Dimensions that locate the work other trades have to avoid. A color or layer per trade so a reviewer can see who owns the line.

A pretty composite that has no elevations is a picture, not a coordination drawing. The installer needs to know which system is lowest, and where a valve can still be reached after the ceiling closes.

Each trade signs the zones it accepts. A trade that will not sign should mark the conflict with a dimension, not a general objection. The contractor resolves it or sends an RFI when the contract drawings cannot contain the work.

An RFI that says the trades do not fit, without the overlay and the elevation that failed, is hard for the engineer to answer. The coordination drawing is the attachment.

The architect or engineer reviews shop drawings for conformance with the design. The coordination drawing records that the trades have agreed on a route. One stamp does not do the other job. A shop drawing can be approved and still clash with a neighbor that was submitted a week later.

Sequence the submissions so the composite is updated when a late approval moves a main. An overlay signed against an old shop drawing is how prefabricated racks show up short.

Many projects build the overlay in a coordination model. The crew still needs a sheet or a view with elevations and a sign-off. A model only the VDC lead can open does not instruct the foreman on the morning the inserts are drilled.

If the contract asks for both, say which one governs when they disagree. The usual answer is the signed drawing, updated to match the model the trades accepted.