CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationHard
A contractor is preparing for a monolithic slab pour on a residence with underslab plumbing and electrical conduit. Which sequencing step is essential before the concrete pour proceeds?
- AInstalling insulation and vapor barrier before the plumbing and electrical rough-in is complete
- BObtaining inspection approval of underslab plumbing and electrical rough-in while trenches remain open and visible
- CBackfilling all trenches immediately after pipe installation to save time
- DPouring the slab first, then cutting trenches afterward for underslab utilities
Show answer & explanationAnswer & explanation
Correct answer: B. Obtaining inspection approval of underslab plumbing and electrical rough-in while trenches remain open and visible
Underslab plumbing and electrical work must be inspected and approved while still exposed in open trenches, since these systems will be permanently concealed once the slab is poured. Backfilling or pouring before inspection prevents verification of proper installation and typically fails inspection requirements.
Why the other options are wrong
- A. Vapor barrier and insulation should follow, not precede, completed and inspected underslab rough-in work.
- C. Backfilling before inspection conceals the work and prevents code verification.
- D. Cutting trenches after the pour is impractical and not standard practice for underslab utilities.
Underslab Rough-In Inspection Sequencing
Underslab plumbing and electrical systems must be inspected and approved while trenches remain open, before concrete is poured over and permanently conceals the work.
- Concealment before inspection typically requires costly rework or exposure.
- Vapor barrier/insulation placement follows approved underslab rough-in.
- Inspectors need visual access to verify pipe sizing, slope, and conduit placement.
Memory trick: 'Inspect it before you conceal it in concrete.'