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.

What is the Plumbing Rough-In Dimensions Reference?

A searchable reference of standard plumbing rough-in dimensions including drain center-to-wall, supply height above finished floor, and valve offsets for common fixtures, cross-referenced to typical IPC and UPC practice. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Plumbing Rough-In Dimensions Reference

Name: Plumbing Rough-In Dimensions Reference
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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

Fixture-by-fixture guidance

Toilet

The standard residential toilet rough-in is 12 inches from the finished wall to the center of the flange. Older homes sometimes have 10-inch or 14-inch rough- ins; measure to the bolt caps to confirm before ordering a fixture. The cold supply is typically stubbed out about 6 inches AFF and 6 inches to the left of the flange center. Leave at least 15 inches of clearance from flange center to any side wall or obstruction (18 inches preferred; ADA requires 18 inches to the near side and 60 inches to the opposite wall or fixture).

Lavatory (bathroom sink)

Hot and cold supplies are typically set about 20 to 22 inches AFF, spaced 8 inches on center (hot on the left, cold on the right). The drain center rough-ins near 18 to 19 inches AFF. Vessel sinks require supplies and drain higher — always check the fixture spec sheet.

Kitchen sink

A standard kitchen sink drain centers near 16 to 18 inches AFF under the counter. Supplies rough in at roughly 22 inches AFF, spaced to match the faucet or the supply valve positions. For double-bowl sinks the drain often falls between the two bowls.

Tub/shower valve and head

A combination tub-and-shower valve typically sits at 28 inches AFF (measured to the valve center) to allow comfortable use from the tub. A shower-only valve centers between 38 and 48 inches AFF to suit standing users. The shower head arm is traditionally roughed in at 78 to 80 inches AFF — adjustable arms can correct for non-standard framing.

Water heater

The cold inlet and hot outlet are both 3/4-inch connections, almost always at the top of the tank. Leave enough clearance for the T&P (temperature and pressure) relief valve discharge tube, which the IPC and UPC require to terminate within 6 inches of the floor.

The critical finished-surface offset

All rough-in dimensions are to the finished surface — the face of drywall or tile, and the finished floor height after flooring is installed. If you are measuring from bare studs or sub-floor, add:

Drywall: typically 1/2 inch (12.7 mm) on each wall face.
Tile over backer: add 5/8 to 3/4 inch for backer plus tile.
Floor tile or LVP over sub-floor: add 3/8 to 1/2 inch.

Failing to account for finish thickness is the most common cause of toilets that will not seat against the wall or supply lines that land behind the fixture.

Always verify against the manufacturer spec sheet

Wall-hung toilets, vessel sinks, and freestanding soaking tubs have widely varying rough-in requirements that bear little resemblance to the standard figures. Pull the rough-in drawing for your specific model before cutting any hole or soldering any stub-out.