Module 12 · Lesson 8
Rough Plumbing, Electrical and HVAC
The rough-in stage threads every system through the frame — and ends with the inspections that gate insulation. What's happening in the 'invisible' weeks.
These are the "nothing is happening" weeks (12.1's rhythm; 12.7's warning) — while inside the frame, three trades install everything your walls will ever contain. "Rough" means the parts that live inside walls and ceilings, installed before insulation hides them forever. Here's what each trade is doing in there.
Rough plumbing. Supply lines to every future fixture, drain-waste-vent piping (your Module 7.4 gravity math, executed at ¼ inch per foot), and the vents that run to the roof. The shower valve goes in now (the trim you see later just decorates it); the washer box, the water heater's connections (that HPWH closet from 7.8), and — small detail, big deal — nail plates: steel guards where pipes pass through studs, so next month's drywall screws can't find them. Rough plumbing ends with a pressure test the inspector witnesses: the system holds pressure or it doesn't pass. Binary, beautiful.
Rough electrical. The subpanel (or new service — Module 7.2's decision, executing), circuits home-running to it, boxes at every outlet, switch, and fixture location, and the dedicated circuits your load calc promised (7.3). This is when lesson 12.4's advice pays off: outlet and switch positions are still movable-ish this week. Smoke and CO detector wiring goes in per code (lesson 10.2's life-safety items, becoming copper).
Rough HVAC. The mini-split linesets and condensate drains (7.7), any ducting for the ducted version, bath fans ducted to the outside (lesson 8.3's hill worth dying on), and the range hood duct (8.2's other hill). Equipment mostly arrives later; pathways happen now.
The choreography. Order matters even within the stage: plumber first (big pipes claim territory), HVAC second (ducts need what's left), electrician third (wire bends around everything). A GC sequencing this well is invisible; sequenced badly, it's a month of trades undoing each other — one more thing lesson 11.11's owner-builders discover they're conducting.
The finale: rough inspections — plumbing, electrical, mechanical, sometimes in one visit, sometimes several. Only after all pass does insulation get its green light. Everything in the walls has now been verified by someone whose job is doubting it. That's the system working (12.11 makes it official).
Key takeaways
- Rough-in installs everything that lives inside walls: supply/drain/vent, circuits and boxes, linesets and ducts.
- The trades take turns by territorial logic: plumbing, then HVAC, then electrical.
- Pressure tests and rough inspections verify it all before insulation buries it — the gate is the point.
- This is the last cheap week to move an outlet; speak at rough-in or hold your peace.