Rough-In Plumbing: Stages, Inspection, and What It Covers
Rough-in plumbing is the stage where a plumber installs every drain, waste, vent, and water supply pipe inside the walls, floors, and ceilings before those surfaces are closed. No fixtures are set. The work is pressure-tested and inspected while each joint sits exposed, then insulation and drywall go up. Finish plumbing comes later, once fixtures are connected.
What is rough-in plumbing?
Rough-in plumbing is the hidden framework of a plumbing system: the pipes behind walls and under floors that carry water in and waste out. A plumber sets the drain-waste-vent (DWV) lines and the water supply runs to each fixture location, caps or stubs them out, then tests the system. Fixtures like sinks and toilets wait for the finish stage.
The name is literal. This is the rough work, done while framing is open and before anything gets covered. Getting pipe sizing, slope, and placement right here is what makes the visible fixtures work later, and mistakes are expensive to fix once drywall hides the pipes.
What are the three phases of plumbing in a build?
A build has three plumbing phases: underground (groundwork) rough-in, above-ground rough-in, and finish (trim-out). The first two together are what most people mean by rough-in plumbing. Each phase ends before the next trade covers the work, and each has its own inspection checkpoint. The table below maps what happens, when, and what the inspector looks for.
| Phase | What happens | When in the build | What the inspector checks |
|---|---|---|---|
| Underground / groundwork rough-in | DWV drain lines set under the slab or in the crawlspace, and the main sewer and water service routed in | After excavation and footings, before the slab is poured | Pipe sizing and slope, correct materials, and a leak-free test before backfill or pour |
| Above-ground rough-in | Supply lines, waste and vent stacks, and any gas lines run through the framed walls and joists, then capped or stubbed out | After framing, before insulation and drywall | Sizing, slope, venting, pipe support spacing, and a pressure or air test with no leaks |
| Finish / trim-out | Fixtures set and connected: sinks, toilets, faucets, shower valves trimmed, water heater hooked up | After drywall, flooring, and cabinets are installed | Fixtures drain and hold pressure, traps and shutoffs in place, no leaks at connections |
Most residential jobs collapse the two rough-in phases into a single stretch of work when there is no slab, so a slab-on-grade house sees a distinct groundwork visit while a home over a basement or crawlspace may not. Either way, the rough-in inspection stands between the plumber and the drywall crew.
DWV vs water-supply rough-in: what is the difference?
Rough-in covers two separate systems. DWV (drain, waste, vent) carries waste out and lets sewer gas escape, and it works on gravity and slope, so pipe is larger, sloped, and vented. Water supply carries pressurized hot and cold water to each fixture in smaller pipe. A plumber roughs in both, but they follow different rules and get tested differently.
DWV lines usually go in first because they are bigger, need slope, and are harder to route around framing. Supply lines thread in around them. Both must land at the exact height and spacing each fixture needs, which is where the room-specific dimensions matter, and where a small error becomes a crooked toilet or a faucet that will not reach.
What is the rough-in sequence, step by step?
Rough-in plumbing follows a set order so that the harder, gravity-dependent lines go in before the flexible ones, and so the system can be tested before anything is covered. The sequence below is the typical residential flow from an open-framed house to an approved, ready-to-cover system.
- Confirm the fixture layout and mark every drain and supply location from the plans.
- Run the main drain and DWV branch lines, holding correct slope, usually 1/4 inch per foot on smaller waste pipe.
- Install vent piping up through the roof line to keep traps from siphoning.
- Route hot and cold water supply lines to each fixture stub-out.
- Secure and support all pipe at code-required spacing, then cap or stub out every line.
- Pressure-test the DWV and supply systems and hold the required pressure with no leaks.
- Call for the rough-in inspection and get approval before insulation and drywall.
What happens at the rough-in inspection and pressure test?
At the rough-in inspection, the inspector confirms sizing, slope, venting, support spacing, and materials meet local code, then watches the system hold a test with no leaks. Everything stays exposed, so this happens before insulation and drywall. DWV is tested first, then supply. Codes vary between the IPC and UPC and by local amendment, so confirm your numbers locally.
The DWV system is usually proven with a water test, a 10-foot head of water above the highest point held for at least 15 minutes, or an air test at about 5 psi for 15 minutes. Plastic DWV pipe is typically tested with water or a vacuum, not compressed air, so check the method your inspector requires.
Water supply lines are tested under pressure, often air at around 50 psi or water at 10 psi above working pressure, held for 15 minutes with no drop. The system must prove leak-free by visual check while the inspector is present. Whether your job needs this step at all comes down to whether your job needs a permit, which most new work does.
Rough-in vs. finish (trim-out) plumbing
Rough-in plumbing installs the hidden pipes while walls are open and ends with an inspection and pressure test. Finish plumbing, also called trim-out, happens after drywall, flooring, and cabinets are in. Trim-out sets and connects the fixtures you see and use, then a final inspection confirms everything drains and holds pressure. Rough-in is the skeleton; trim-out is the visible body.
The gap between the two phases is deliberate. Once rough-in passes, other trades close the walls, paint, and install cabinets, all of which would be damaged if fixtures were already hanging. Only when the room is finished does the plumber return to set toilets, mount faucets, trim shower valves, and connect the water heater.
How much does rough-in plumbing cost and how long does it take?
Rough-in plumbing often costs about $300 to $600 per fixture, or roughly $4 to $10 per square foot. A 2,000 square foot home with two or three baths and around 15 fixtures commonly lands near $8,000 to $12,000. Time-wise, an average single-family rough-in runs 2 to 5 days, plus scheduling and inspection wait.
Cost climbs with fixture count, long or complex pipe runs, premium materials, and higher-cost labor markets. Timing stretches with larger homes, extra bathrooms, and multi-family builds. Both figures depend on region and on how the layout is drawn, so treat these as planning ranges, not quotes, and get a fixture-count estimate for your own project.
Room-specific rough-in guides
This page defines rough-in plumbing across a whole build. When you need the exact heights, spacing, and pipe sizes for one room, the dimensions differ by fixture and layout. The guides below carry the measured rough-in details for the rooms people plan most often, so use this hub for the concepts and the room pages for the numbers.
- For a full bathroom, see the bathroom plumbing rough-in dimensions, including toilet, sink, and tub placement.
- For a kitchen, see the kitchen plumbing rough-in layout covering the sink, dishwasher, disposal, and ice maker.
- For a shower or tub, see the shower valve and drain rough-in diagram with valve height and drain placement.
Frequently asked questions
What is rough-in plumbing?
Rough-in plumbing is the stage where a plumber runs all drain, waste, vent, and water supply pipes inside the walls, floors, and ceilings before those surfaces are closed. No fixtures are set yet. The system is tested and inspected while every joint is still exposed, then insulation and drywall go up.
What are the three stages of plumbing in new construction?
The three stages are underground (groundwork) rough-in, above-ground rough-in, and finish or trim-out. Groundwork sets the DWV lines under the slab or crawlspace. Above-ground rough-in runs supply and vent piping through the framing. Finish work connects the visible fixtures after walls, floors, and cabinets are in place.
What is the difference between rough-in and finish plumbing?
Rough-in installs the hidden pipes while walls are open, and it ends with an inspection and pressure test. Finish plumbing, also called trim-out, happens after drywall, flooring, and cabinets go in. Finish work sets and connects the sinks, toilets, faucets, and water heater, then a final inspection checks that everything drains and holds pressure.
What does a rough-in plumbing inspection check?
The inspector confirms pipe sizing, slope, support spacing, venting, and materials meet local code, then verifies the system holds a pressure or air test with no leaks. Everything must stay exposed, so the inspection happens before insulation and drywall. Approval lets the build move to closing the walls and, later, trim-out.
How long does rough-in plumbing take?
Rough-in plumbing usually takes 2 to 5 days for an average single-family home, depending on the number of bathrooms and the layout. Larger homes, multi-family builds, and complex routing take longer. Scheduling the inspection and waiting for approval can add days before drywall crews are cleared to close the walls.
How much does rough-in plumbing cost?
Rough-in plumbing often runs about $300 to $600 per fixture, or roughly $4 to $10 per square foot. A typical 2,000 square foot home with two or three bathrooms and around 15 fixtures commonly falls near $8,000 to $12,000. Complex layouts, premium markets, and long runs push the figure higher.
Do you need a permit for rough-in plumbing?
In most areas, yes. New construction, remodels that move or add pipes, and additions almost always require a plumbing permit and at least one rough-in inspection before walls are closed. Rules vary by state and local code, so confirm with your building department before work starts to avoid tear-out later.
Last reviewed: September 2026.