What does a 12-inch toilet rough-in mean?

The rough-in is the distance from the finished wall to the center of the toilet flange waste pipe. Twelve inches is the most common, but 10-inch and 14-inch rough-ins exist for older or unusual layouts. Measure to the bolt caps, not the baseboard.

How high should lavatory supplies be roughed in?

Bathroom lavatory hot and cold supplies are typically set about 20 to 22 inches above the finished floor, with the drain centered near 18 to 19 inches. Spacing between hot and cold is usually 8 inches on center.

What is the standard shower valve height?

A shower-only valve is commonly set 38 to 48 inches above the finished floor, while a tub-and-shower valve sits lower at about 28 inches. The shower head arm typically roughs in at 78 inches. Adjust for tall users.

Do these dimensions satisfy ADA?

No. These are standard residential figures. ADA and accessible fixtures have their own mounting heights, clearances, and reach ranges that override these values. Use the accessibility standard when the project requires it.

Why verify against the manufacturer sheet?

Every fixture model has a specific rough-in drawing showing exact waste and supply locations. Wall-hung toilets, vessel sinks, and freestanding tubs vary widely. The standards here are a planning reference, not a substitute for the model spec sheet.

Plumbing Rough-In Dimensions Reference

Roughing in plumbing before the fixtures arrive means working from standard dimensions. This reference collects the common drain center-to-wall distances, supply heights above finished floor, and valve offsets for the fixtures you meet on a typical residential job, so you can set your drains and stub-outs with confidence.

How it works

There is no formula here, only well-established convention. Each fixture has a drain location, one or two supply locations measured above the finished floor (AFF), and where relevant a valve height. The values below reflect common IPC and UPC residential practice:

toilet      → drain 12 in center-to-wall; supply 6 in AFF, 6 in left of center
lavatory    → drain ~19 in AFF; supplies ~22 in AFF, 8 in apart on center
kitchen sink→ drain ~16 in AFF; supplies ~22 in AFF
tub/shower  → valve 28 in AFF (tub) / 38–48 in (shower); head arm 78 in AFF
water heater→ cold/hot 3/4 in connections at top; T&P discharge to within 6 in floor

These are reference numbers. The exact waste and supply positions always come from the fixture’s own rough-in drawing.

Example and notes

When framing a standard bathroom, you might set the toilet flange center 12 inches from the finished wall, lavatory drain near 19 inches AFF with supplies at 22 inches, and a tub/shower valve at 28 inches with the head arm at 78 inches. Always add the thickness of finished wall and floor materials to your measurements: a 12-inch rough-in is to the finished surface, so if you measure from bare studs you must account for the drywall and tile thickness.