Bathroom sink rough-in heights and double-vanity centerline spacing
Rough-in: the drain stubs 18–20″ above the finished floor, the supplies 20–22″. An 8″ widespread faucet drills 3 holes (one 4″ each side of center); centerset is 3 holes 4″ apart; single-hole is 1. Two sinks need centerlines ≥30″ apart (IRC P2705.1.5; NKBA 36″), so a double vanity runs 60″ or wider.
What this diagram shows
A back-wall elevation of a double vanity showing where the plumbing rough-in lands. Each sink drain stubs out 18 to 20 inches above the finished floor and the hot and cold supplies stub out 20 to 22 inches above the floor. An 8-inch widespread faucet drills three holes, one at the sink centerline and one 4 inches to each side; a centerset faucet drills three holes 4 inches apart and a single-hole faucet drills one. For two sinks the centerlines must be at least 30 inches apart per IRC P2705.1.5, with NKBA recommending 36 inches, which is why a double vanity has to be at least 60 inches wide. The hot supply is drawn on the right and the cold on the left of the left sink.
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