Bathroom Plumbing Rough-In Dimensions Guide

Toilet Rough-In Measurements

The toilet rough-in is the distance from the finished wall to the center of the closet flange (drain) in the floor. The standard rough-in is 12 inches, but 10-inch and 14-inch rough-ins exist. Measure from the finished wall surface, not the baseboard. The center of the toilet must be at least 15 inches from any side wall or adjacent fixture (18 inches is recommended for comfort). The supply valve should be located 6 inches to the left of the toilet center, about 6 inches above the floor.

Sink and Vanity Rough-In

The standard bathroom sink drain rough-in is 18 to 20 inches above the finished floor, centered on the vanity location. The hot and cold supply lines should be 20 to 22 inches above the floor, spaced 4 inches apart (2 inches on each side of center). If installing a wall-mounted sink (no vanity), the drain and supply locations must be precisely matched to the sink manufacturer's specifications, as there is no vanity cabinet to conceal the plumbing. Allow at least 4 inches between the edge of the sink and any side wall.

Shower and Tub Rough-In

Shower valves are typically roughed in at 48 inches above the floor, centered on the shower width. The shower head outlet is roughed in at 72 to 80 inches above the floor. The shower drain is centered in the shower floor (for point drains) or along one wall (for linear drains), connected with a 2-inch drain pipe. Bathtub drains require a 1-1/2 inch drain and overflow connected to a trap, with the tub spout roughed in at 4 inches above the tub rim and the valve at 28 to 30 inches above the floor. All measurements should be verified against the specific fixture manufacturer's roughing-in dimensions.

Venting Requirements

Every bathroom fixture requires proper venting. Toilets need a 2-inch vent (3-inch in some codes), sinks need a 1-1/2 inch vent, and showers need a 1-1/2 to 2-inch vent. The vent must connect to the drain within a specific distance from the trap (called the trap arm length) — 6 feet for a 1-1/2 inch pipe and 10 feet for a 2-inch pipe. If distance to the vent stack exceeds these limits, an air admittance valve (AAV) may be used if allowed by local code. Plan vent routing before framing the walls to ensure adequate space in the stud bays.