Rough-in is the phase where electrical, plumbing, and HVAC systems are installed inside the open wall, floor, and ceiling cavities before insulation and drywall close everything up. It has to happen in the right sequence, it requires licensed professionals in most jurisdictions, and the inspections that follow it are among the most important in the entire build.
The Rough-In Sequence
Rough-in work typically follows a specific sequence that respects how the trades work in relation to each other:
- Plumbing rough-in first. Drain, waste, and vent (DWV) pipes are large diameter and difficult to route around other systems. Plumbers need to run pipes through framing members (with notches or holes drilled through studs and joists) before electrical and HVAC occupy that space. Supply lines follow the DWV work.
- HVAC rough-in second. Ductwork, if you're using a forced-air system, also takes up significant space and is easiest to route when electrical hasn't yet filled the cavities. Mini-split systems have smaller footprints and more installation flexibility, which is part of why they've become popular in cabin builds.
- Electrical rough-in last. Wiring is thin, flexible, and easy to route around existing plumbing and HVAC. Boxes are mounted, cables are run between them, and everything is positioned for the devices and fixtures that will be installed later.
Electrical Rough-In
Electrical rough-in establishes the entire wiring infrastructure of the building. This includes:
- Service panel location and main feed from the utility connection or solar system
- Circuit layout — which outlets, fixtures, and appliances are on which circuits
- Box mounting for all outlets, switches, and fixture locations
- Cable routing between panel and all boxes
- Dedicated circuits for high-draw appliances (range, dryer, HVAC)
Rough-in electrical requires a licensed electrician in most jurisdictions. The rough-in inspection — conducted before walls are closed — verifies that box heights, wire gauges, circuit protection, and connections meet code. Do not close walls before this inspection is passed.
Plumbing Rough-In
Plumbing rough-in establishes the supply and drain infrastructure for every fixture in the building:
- Drain, waste, and vent (DWV) pipes from fixtures to the main drain or septic connection
- Hot and cold supply lines from the water heater or on-demand heater to all fixtures
- Stub-outs at each fixture location (shower, toilet, sink, dishwasher, washing machine)
Like electrical, plumbing rough-in requires a licensed plumber in most jurisdictions and is subject to a rough-in inspection before walls close. Plumbing inspections often include a pressure test to verify there are no leaks in supply lines before they're enclosed.
HVAC Rough-In
For cabin builds, HVAC choices vary significantly based on size, climate, and whether the build is on or off the grid:
- Mini-split systems (the most common choice for cabin builds) require refrigerant line sets run between the indoor air handler and the outdoor compressor, plus electrical connections. Line set routing happens during rough-in.
- Forced-air systems require full ductwork runs through floor and ceiling cavities. These are more complex to install in a post-frame cabin than in a conventionally framed house.
- Radiant floor heating requires tubing installation before concrete or subfloor goes down — earlier in the sequence than other HVAC systems.
- Wood stoves require blocking and backing installed in the framing phase, and chimney penetration through the roof structure.
What the Rough-In Inspection Covers
The rough-in inspection (sometimes called a "rough inspection" or "mechanical inspection") is conducted after all rough-in work is complete but before any insulation or wallboard covers it. Inspectors verify:
- Electrical: box locations, wire gauges, panel connections, required arc-fault and ground-fault protection
- Plumbing: pipe sizing, venting, trap placement, drain slope, pressure test results
- HVAC: equipment sizing and installation, refrigerant line protection, combustion air provisions for any fuel-burning equipment
This inspection is not optional and is not something to try to avoid. Calling it in promptly keeps your project on schedule.
Bottom Line
Rough-in is the phase that most directly requires licensed professional trades. It's also the phase where the cost of getting it wrong is highest — tearing open finished walls to correct plumbing or electrical mistakes is among the most disruptive and expensive remediation work in residential construction. Do it right the first time.