A rough-in is the phase of construction when plumbing pipes, electrical wiring, and HVAC ductwork are installed inside walls, floors, and ceilings before those surfaces are closed up with drywall or other finishes. It happens after the framing is complete but before any fixtures, outlets, or visible finishes go in. Think of it as building the hidden infrastructure of a house or building.
What Gets Installed During a Rough-In
The rough-in phase covers three main systems, often called the “MEP” trades: mechanical (heating and cooling), electrical, and plumbing. Each trade runs its components through the open framing so everything is in position before walls are sealed.
- Plumbing rough-in: Drain, waste, and vent (DWV) pipes, water supply lines, and built-in fixture supports. This means the pipes that will eventually connect to your sinks, toilets, showers, and washing machine are all placed and connected, but the actual fixtures aren’t attached yet. Vent pipes that allow air into the drainage system are also run up through the roof at this stage.
- Electrical rough-in: Wiring is pulled through the framing to every location that will have an outlet, switch, or light fixture. Junction boxes are nailed to studs, and wires are run back to the electrical panel. No switches, receptacles, or light fixtures are installed yet, just the boxes and cables.
- Mechanical (HVAC) rough-in: Ductwork for heating and cooling is installed, along with furnace placement, refrigerant lines for air conditioning, and exhaust venting. Ducts are sealed at joints with mastic or approved sealant, and metal ducts are supported at least every 10 feet. If the home has a forced-air furnace, the unit’s location must meet specific clearance requirements, including 30 inches of working space in front and at least 3 inches along the sides, back, and top.
In some projects, low-voltage wiring for internet, cable, security systems, and speakers is also run during the rough-in, since these cables need to be inside walls before drywall goes up.
Where Rough-In Falls in the Construction Timeline
Rough-in work begins after the structure is framed and the roof is on, which protects the interior from weather. The typical sequence looks like this:
- Foundation and framing go up first.
- Rough-in for plumbing, electrical, and HVAC happens next, often with plumbing going first since drain lines are the least flexible in terms of routing.
- Insulation is added after rough-in work passes inspection.
- Drywall goes up, sealing everything inside the walls.
- Trim-out or finish is the final step, when fixtures, outlets, switches, faucets, and registers are connected to the rough-in work hidden behind the walls.
The gap between rough-in and finish is significant. In a typical new home build, weeks or even months may pass between when the plumber runs pipes and when they return to install sinks and toilets.
Why the Rough-In Inspection Matters
Before anyone can hang drywall, a building inspector must examine the rough-in work for each trade. This is one of the most important inspections in the entire construction process because it’s the last time these systems will be visible and accessible. Once drywall covers everything, fixing a mistake means cutting open walls.
During a rough-in inspection, the inspector checks that permits and approved plans are on site, then verifies that each system meets building code requirements. For a mechanical rough-in, that includes checking duct leakage (which must stay below 4 cubic feet per minute per 100 square feet of floor area with an air handler installed), verifying clearances between heat-producing equipment and combustible materials, and confirming that fuel-burning appliances aren’t installed in bedrooms or bathrooms unless they’re direct-vent models.
Inspectors also look for practical safety details. Protective steel plates must be installed where nails or screws could puncture pipes or ducts hidden behind the wall surface. Dryer exhaust ducts can’t exceed 35 feet in length and must have smooth interior surfaces with joints running in the direction of airflow. An electrical receptacle is required within 25 feet of each major appliance, and a disconnect switch must be within sight of the unit.
If a rough-in fails inspection, the contractor corrects the issues and calls for a re-inspection before the project can move forward.
Rough-In Dimensions and Measurements
When contractors talk about “rough-in measurements,” they’re referring to the precise locations where pipes, wires, or ducts emerge from walls or floors. These measurements determine where your fixtures will end up. A toilet rough-in, for example, is measured from the finished wall to the center of the drain pipe in the floor. The standard toilet rough-in is 12 inches, though 10-inch and 14-inch rough-ins exist in some homes.
Getting these measurements right during rough-in is critical. If a shower valve is roughed in at the wrong height, or a sink drain is off by a few inches, the fixture either won’t fit or will look wrong. Contractors work from detailed plans that specify the exact position of every pipe stub, electrical box, and duct opening.
What Rough-In Costs Cover
If you’re getting a bid for a remodel or new construction, you’ll often see rough-in costs listed separately from finish or trim-out costs. The rough-in portion covers all the labor and materials for running pipes, wires, and ducts through the structure. The finish portion covers connecting fixtures, installing outlets and switches, and hooking up appliances.
Rough-in work typically represents the larger share of total plumbing and electrical costs because it involves more labor-intensive work: cutting through framing, routing long pipe and wire runs, and coordinating between trades so that a plumber’s drain line doesn’t conflict with an electrician’s wire path or an HVAC installer’s duct run. In renovation projects, rough-in costs can climb higher because existing walls may need to be opened up and the work must tie into older systems that may not match current code standards.
Rough-In for Remodels and Additions
Rough-in isn’t just a new-construction term. Any remodel that moves plumbing fixtures, adds electrical circuits, or extends ductwork involves rough-in work. Adding a bathroom to a basement, for instance, requires roughing in drain lines (sometimes by cutting into the concrete slab), running new water supply lines, and extending vent pipes. The same inspection requirements apply: an inspector needs to see the work before walls are closed.
If you’re planning a future bathroom or kitchen in an unfinished space, some builders will rough in the plumbing during initial construction. This means placing drain and supply lines in the slab or walls even though no fixtures will be installed yet. It’s far cheaper to rough in plumbing before concrete is poured than to jackhammer a finished slab later.