Rough-In Plumbing

Rough-in plumbing is the first phase of a plumbing installation, completed before drywall, tile, or finish surfaces go up. During rough-in, a plumber installs all the pipes, drain lines, and vent stacks that will be hidden inside walls, floors, and ceilings — leaving stub-outs at the locations where fixtures will eventually connect.

What happens during rough-in plumbing?

• Supply lines (hot and cold) are run from the main shutoff to each fixture location
• Drain-waste-vent (DWV) pipes are installed with correct slope (¼ inch per foot for horizontal drains)
• Vent stacks are run up through framing to the roof
• Stub-outs are capped and left protruding from walls at code-required heights
• Inspection is scheduled — most jurisdictions require a rough-in inspection before walls close

Rough-in dimensions are the measurements from a finished wall or floor to the center of a drain or supply stub-out. These numbers must match the fixture you're installing. Common rough-in dimensions:

• Toilet: 12 inches from finished wall to drain center (some older homes are 10 or 14 inches)
• Bathroom sink: 18–21 inches above finished floor for drain stub-out
• Shower: drain centered in the pan, supply valve 48 inches above finished floor
• Kitchen sink: drain stub-out 18–20 inches above finished floor

Why does rough-in matter?

Errors at this stage are expensive to fix after drywall is hung. If a toilet rough-in is 10 inches instead of 12, you need a special offset flange or a completely different toilet model. Getting rough-in dimensions verified before walls close is the job of both the plumber and the general contractor.

What does rough-in plumbing cost?

Rough-in plumbing for a new bathroom addition runs $1,500–$4,500 depending on complexity, distance from existing stacks, and local permit fees. Full-house rough-in on new construction runs $8,000–$18,000 for a 2,000 sq ft home.