Mechanical, Electrical, and Plumbing Coordination / Specialty Construction
Coordination fundamentals
The GC owns coordination even when each trade installs its own system. Use coordination drawings and clash detection before rough-in, and follow the standard priority: gravity lines first (drains), then pressure piping, then ductwork, then conduit. Sleeves and openings must appear on the structural drawings and be approved by the engineer of record. Every penetration of a rated wall or floor needs an approved firestop system tested to ASTM E814 and listed by UL; ducts crossing rated walls need fire dampers, and smoke dampers where the code requires smoke barriers.
Mechanical
One ton of cooling equals 12,000 BTU/hr - this is the single most tested conversion. Load calculations drive CFM per room; ducts are sized by friction rate or velocity. Test, adjust, and balance after installation. Provide access panels at dampers, valves, and coils, a trapped condensate drain, code-required clearances, and seismic restraints where applicable.
Electrical
Ampacity and derating, panel schedules, load calculations, and voltage drop (common rule: 3% branch, 5% total). GFCI protection for kitchens, baths, outdoors, garages, and temporary power; AFCI in dwelling bedrooms. Grounding and bonding is a complete system, not a single rod.
Plumbing
Drainage slope: 1/4 in per foot for 2 in pipe and smaller, 1/8 in per foot for 3 in and larger. Every fixture trap needs a vent to prevent siphonage. Hydrostatically test DWV before closing walls. Water heaters need a temperature-and-pressure relief valve piped to a safe discharge and a drain pan where required.
Worked example
A 600 sf room at 1 CFM/sf needs 600 CFM. A 3-ton unit at 400 CFM/ton delivers 1,200 CFM - enough for two such rooms. If two numbers in a question do not reconcile, one is a distractor.
Traps: treating 1 ton as 1,000 BTU, skipping firestopping, or confusing fire dampers with smoke dampers.