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Construction glossary · MEP

What is plumbing rough-in in construction?

Plumbing rough-in in construction is the phase where all the in-wall, overhead, and underground piping is installed before walls close and fixtures set: the drain, waste, and vent (DWV) lines, the hot and cold water distribution, and the stub-outs each fixture will connect to. It happens in two passes, an underground rough before the slab pours and an above ground rough (top-out) after framing, each inspected and pressure tested before cover. Estimators commonly shorthand its cost per fixture.

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Updated September 2026 · Reviewed by the Ruh construction team

Measured in per fixture or lfPasses underground + top-outIllustrative rate $1,800/fixtureCost driver fixture grouping
The definition

Plumbing rough-in, explained.

Rough-in is the phase when a building's concealed systems are installed and inspected before walls, ceilings, and other finish surfaces close. Roughed in means that concealed work is installed and tested but the fixtures are not yet set. Electricians, mechanics, and plumbers all use the word for their own in-wall pass, and plumbing rough-in is the version every plumbing bid is built around. The scope comes off the P sheets: floor plans, the waste and vent riser, the water riser, and the fixture schedule, with the plumbing subcontractor owning all of it. The work lands in two mobilizations: the underground rough goes in after foundations and before the slab pours (DWV laid in trenches, stubbed up at future walls), and the above ground rough, which the trade calls top-out, fills the framed walls and ceilings with supply, waste, and vent piping ending at stub-outs and test caps. Because rough-in is so repeatable, estimators shorthand it per fixture, and that is also where they get burned: the per-fixture average assumes fixtures grouped into restroom cores, so a job with scattered fixtures, long horizontal runs, or wall-hung fixtures on carriers (expensive rough-in hardware) breaks the average quietly. The other miss is schedule: the plumber mobilizes with the foundation crews, months before finishes.

Fieldwire frames rough-in as a construction-wide stage. Electrical and HVAC or mechanical crews run their own in-wall pass in the same window, so the trades' rough-ins stack before drywall on the schedule, as ServiceTitan explains.

How it is measured

Two methods coexist. For budgets, estimators count fixtures each off the fixture schedule and multiply by a per-fixture rough-in rate from their own history, a deliberate shorthand that bundles pipe, fittings, and labor into one number. For a hard bid, the takeoff goes to detail: DWV piping in lf by size and material (cast iron versus PVC matters), water piping in lf by size (copper versus PEX), fixture carriers each, cleanouts each, and vent terminations through the roof each. Cost drivers: fixture grouping (back-to-back restroom cores share stacks and carriers, scattered fixtures do not), underground versus overhead routing, and floor construction, since a podium slab turns simple drops into core drills and sleeves. The fixture schedule, waste and vent riser, and water riser are the controlling sheets.

How much does plumbing rough-in cost per fixture?

Estimators budget plumbing rough-in with a per-fixture shorthand rate drawn from their own job history. The worked example below uses an illustrative $1,800 per fixture, so a 14-fixture tenant improvement budgets at 14 x $1,800 = $25,200. The rate bundles pipe, fittings, and labor into one number, and it holds when fixtures group into restroom cores. Scattered fixtures, long horizontal runs, wall-hung fixtures on carriers, or cast iron DWV all push the real cost past the average, which is why hard bids back the shorthand with a detailed lf takeoff.

What is plumbing top-out?

Top-out is the above ground half of rough-in: after framing, the plumber fills the walls and ceilings with supply, waste, and vent piping, ending at stub-outs and test caps, with vents carried up through the roof. It follows the underground rough, which placed the below-slab DWV before the pour.

What happens at a plumbing rough-in inspection?

The DWV system gets a water or air test, while the supply side gets a pressure test. The work stays uncovered until it passes.

Sign-off follows the construction sequence: underground, top-out, then final. The rough-in inspection closes concealed piping work; fixture installation and final connections wait for finish plumbing.

Kulk's Plumbing describes the same boundary between rough-in plumbing and finish plumbing: rough-in ends with concealed lines ready for inspection, while fixtures and final connections belong to finish plumbing.

How does rough-in differ on new construction?

New construction carries both rough-in passes. The underground rough follows foundations and precedes the slab pour, so the plumber mobilizes with the foundation crews months before fixtures and finishes.

The worked example is a 14-fixture tenant improvement on an existing slab. A TI often skips the underground pass or cores into it, then proceeds to top-out.

Worked example

A worked plumbing rough-in example.

Worked example

Per-fixture shorthand (illustrative)14 x $1,800 = $25,200
DWV piping (illustrative)220 lf x $38 = $8,360
Water piping (illustrative)340 lf x $22 = $7,480
Carriers, vents, valves (illustrative)$5,100 + $1,200 + $3,000 = $9,300
Detail takeoff total$8,360 + $7,480 + $5,100 + $1,200 + $3,000 = $25,140
How Ruh handles it

How Ruh handles plumbing rough-in.

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Plumbing rough-in: frequently asked questions

What is included in a plumbing rough-in?+

All piping installed before surfaces close: underground DWV beneath the slab, in-wall and overhead waste, vent, and water distribution, stub-outs and test caps at every fixture location, fixture carriers for wall-hung units, and in-wall valves. It excludes the fixtures themselves, faucets, and final connections, which belong to the trim-out phase. The dividing line is simple: rough-in is everything that would be painful to reach after drywall, trim is everything you can still touch.

What is the difference between rough-in and top-out in plumbing?+

Top-out is the second half of rough-in. The underground rough places below-slab DWV before concrete pours; top-out fills the framed walls and ceilings with supply, waste, and vent piping before cover.

How accurate is pricing plumbing rough-in per fixture?+

Good enough for budgets when the job looks like the history behind the number: grouped restroom cores, normal ceiling heights, conventional materials. The shorthand drifts when fixtures scatter, when wall-hung fixtures add carriers, when the structure forces core drilling, or when the DWV runs cast iron instead of PVC for acoustic reasons. Treat the per-fixture rate as a sanity check on a detailed lf-based takeoff for hard bids, not a substitute, and track your own history by building type.

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Related terms

DWV (drain waste vent)Copper pipe typesWater heaterPEXFixture unit

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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.

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