CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationMedium
A contractor is coordinating rough-in work in a bathroom where the HVAC duct, electrical conduit, and plumbing drain line all need to pass through the same wall cavity. What is the best practice to avoid a failed rough-in inspection?
- AWait until drywall is installed to resolve any spatial conflicts
- BInstall whichever trade arrives on site first without coordination meetings
- CInstall all three systems simultaneously in the same cavity regardless of clearance
- DHold a pre-rough-in coordination meeting and sequence installation based on space and slope requirements
Show answer & explanationAnswer & explanation
Correct answer: D. Hold a pre-rough-in coordination meeting and sequence installation based on space and slope requirements
Coordinating trades before rough-in begins, and sequencing installation based on which systems have the least flexibility (such as gravity-dependent drain lines), prevents clashes and rework, helping the project pass inspection on the first attempt.
Why the other options are wrong
- A. Waiting until after drywall makes conflicts far more costly and disruptive to resolve.
- B. First-come installation without coordination often causes clashes that fail inspection.
- C. Simultaneous installation without clearance planning risks code violations and damage.
MEP Coordination Meetings
Pre-rough-in coordination between trades ensures systems with the least flexibility (like sloped drain lines) are installed first, minimizing conflicts in shared cavities.
- Drain lines need consistent slope and have the least flexibility
- HVAC ducts often need the most space
- Electrical conduit is generally the most flexible to reroute
- Early coordination prevents costly rework and failed inspections
Memory trick: Slope wins first, wiring bends last.