Coordinating mechanical and electrical routes on smaller projects
The ductwork shop drawings arrive on Monday, the sprinkler layout on Wednesday and the electrical layout not at all. There is no 3D model and no budget for one, and the corridors have 450 mm between the underside of the beams and the ceiling grid. Installation starts in three weeks.
On design-bid-build work the engineer's mechanical and electrical drawings are usually diagrammatic: they set the scope and materials but not the exact layout, so each trade routes its own system. A Stanford University research paper describes the traditional check: the trades meet to overlay their drawings, draw sections where space is congested, decide who moves, and send the problems that need the engineer as requests for information (RFIs).
- Collect every trade's layout at one scale on the structure and reflected ceiling plan, with sizes and bottom elevations including insulation, hangers and supports.
- Overlay in order of flexibility: ductwork first, since it is largest and has the fewest places to go, then the heating and cooling piping that serves it, then gravity drainage, which must keep its slope; pressure piping, sprinklers and electrical last.
- Draw sections at the tight spots: beam crossings, shafts, and anywhere three systems meet.
- Mark each clash and decide who moves, with the foremen or detailers in one meeting; the more flexible system usually moves.
- Send design questions as RFIs: a change to a size, slope, fire separation or structural penetration is the designer's call — see RFIs that get answered.
- Mark what must stay reachable: access doors, valves, dampers and service space.
- Have each trade sign the layout, then walk the space with the foremen and mark main routes on the deck before hangers go in.
Common mistakes
- Letting the first trade on site set the routes.
- Overlaying without insulation, hangers and fittings, so the drawing clears and the ceiling does not.
- Plans only, with no sections at the crossings.
- Settling a design question on site without the engineer.
Checklist
For the coordination meeting
- Layouts at one scale, on one background
- Bottom elevations with insulation and hangers
- Overlay starting with ductwork and drainage
- Sections at every tight crossing
- One trade assigned to each clash
- Design questions sent as RFIs
- Access doors and service space marked
- Signed layout and routes marked on the deck
Check your understanding
Why start the overlay with ductwork and gravity drainage rather than the electrical layout?
