7.8 Project & Trade Coordination

Project Trade Coordination for Class B General Building

Class B work is defined by multi-trade construction. Coordination is the management system that keeps plumbing, electrical, HVAC, framing, envelope, and finish crews from destroying each other’s work—or the structure. Poor coordination shows up as illegal joist notches, failed rough inspections, and change orders blamed on “unforeseen conflicts” that were visible on the plans.

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Coordination Tools That Actually Work

On larger commercial jobs, BIM clash detection is common. On production residential jobs, a disciplined superintendent with colored plan overlays still prevents most disasters.

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Rough-In Sequencing Hierarchy

Physical flexibility drives order:

1. Gravity DWV — Must hold CPC slope (commonly ¼ in/ft for smaller drains). Route first through joist bays and walls.
2. Large HVAC trunks / exhaust — Rigid sheet metal occupies volume; cannot snake like cable.
3. Fire sprinkler mains (when required) — Hydraulic layout constraints.
4. Supply water / gas / hydronic — Pressurized; more flexible but still need nail plates and support.
5. Line-voltage electrical — Flexible relative to pipes/ducts; still needs box layout and panel clearances.
6. Low-voltage / fire alarm / data — Last; keep separation from power to limit interference.

Framing protection reminder: CBC wood-framing rules prohibit notching joists in the middle third of the span; bored holes are capped (commonly ≤⅓ depth) and must keep edge distances. Coordination that “needs a notch in the middle” is a redesign problem, not a sawzall problem.

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RFIs and Clash Avoidance in Practice

A useful RFI states sheet references, measured field condition, code/constructability impact, and a clear question. Example: “S-5 shear wall at Grid B conflicts with A-4 plumbing chase; 3-inch ABS stack eliminates required double end stud. Request relocation of stack or alternate shear path.”

Clash categories to hunt early:

• Structural beams vs. duct mains
• Hold-downs vs. plumbing wet walls
• Panel clearances vs. water heaters or shelving
• Skylight shafts vs. truss webs
• Exterior hose bibbs / dryer vents vs. shear panels (each penetration can void nailing zones)

Scenario: On a Los Angeles hillside duplex, the plumber drills a 4-inch hole through the middle third of a 2×10 floor joist to keep a tub drain lined up with the fixture. The electrician follows and notches the same joist top edge for NM cable.

Coordination failure: The superintendent never held a wet-wall/MEP layout meeting after joist installation. Repair now requires sistering or engineer-directed reinforcement, delayed drywall, and a framing correction notice. Prevention: layout drains on the joist plan before boring, and reject middle-third notches outright.

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Schedule Logic Beyond “Who Shows Up First”

Coordination includes weather and inspection logic:

• Dry-in before moisture-sensitive finishes — Drywall, wood flooring, and insulation after roof covering and WRB continuity.
• Special inspection before pour/cover — Epoxy anchors and welds cannot be inspected after concealment.
• HERS tests before finals that assume sealed ducts — Changing ducts after a passed duct blaster invalidates results.
• Lath inspection before finish stucco — Many CA jurisdictions require WRB/lath approval first.
• Firestopping before concealment — Rated penetrations fail finals if stuffed with ordinary fiberglass.

Trade stacking (plumber, electrician, and HVAC in the same hallway the same morning) without assigned zones creates damage and finger-pointing. Assign rooms or floors and enforce exclusive access when needed.

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Subcontract Language That Supports Coordination

Weak scopes say “install per plans.” Stronger Class B practice requires:

• Attendance at coordination meetings
• Protection of other trades’ work
• Installation of nail plates, firestops, and seismic bracing specified for that trade
• 48-hour notice before inspections the sub will cause
• As-built documentation of concealed routes
• No structural cutting without GC and, when required, engineer approval

The GC remains accountable to the owner and CSLB for the overall project even when a specialty C-licensee performs the craft. Coordination is how the B license exercises that responsibility on a multi-trade job.

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Clash Avoidance Walkthrough (Residential Example)

Before mechanical rough-in on a two-story Type V dwelling, mark on the floor framing plan:

1. Every tub/shower drain and toilet stack location.
2. Every hold-down post and shear-wall end (no large holes in these packs).
3. HVAC trunk centerline from unit to main drops.
4. Electrical panel and required clearance rectangle.
5. Recessed can lights or skylight shafts that punch the ceiling diaphragm.

Hold a 20-minute meeting with plumbing, HVAC, and electrical leads using that marked plan. Agree who owns each joist bay. Issue a simple written routing note attached to the RFI/coordination log. This low-tech clash review prevents the majority of illegal notches and failed multi-trade rough inspections on California production and custom homes alike.

Change Impact Protocol

When an owner adds a bathroom mid-framing, do not “just squeeze pipes in.” Re-open coordination: confirm fixture units and vents, re-check shear walls, update the look-ahead, and price the change order—including re-inspection risk. Coordination is continuous, not a single kickoff meeting.