Toilet Rough-In & Closet Flange Standards
Direct Answer
Toilet rough-in dimensions under ASME A112.19.2 define the exact centerline distance from the finished rear wall to the closet bolts on the floor flange. While 12.0 inches (305 mm) is the universal modern standard, 10-inch and 14-inch rough-in toilets accommodate legacy plumbing and thick tile remodels, sealing to a 4"×3" closet flange via a wax ring or rubber gasket.
Source: ASME A112.19.2 / CSA B45.1 (Ceramic Plumbing Fixtures)
Specs
| Governing Standards | ASME A112.19.2 / CSA B45.1 / ANSI A112.19.5 |
| Standard Rough-In Distance | 12.0 inches (305 mm) from finished wall to center of flange |
| Alternative Rough-Ins | 10.0 inches (254 mm) compact | 14.0 inches (356 mm) legacy |
| Closet Flange Size | 4" × 3" (fits inside 4" DWV pipe or over 3" DWV pipe) |
| Closet Bolt Spacing & Size | 6.0 inches (152 mm) apart | 5/16"-18 or 1/4"-20 brass bolts |
| Finished Floor Flange Height | Flange bottom must rest flush on top of finished flooring (1/4" proud) |
| Sanitary Water Closet Seal | 100% pure petroleum wax gasket with poly horn or silicone elastomer |
Measuring the 12-Inch Rough-In Dimension
The rough-in distance is measured from the finished rear wall surface (sheetrock plus tile/baseboard) to the center of the floor closet flange bolts. Installing a standard $12\text{-inch}$ toilet on a $10\text{-inch}$ rough-in will cause the ceramic tank to hit the wall before the bowl aligns with the closet bolts, requiring a dedicated $10\text{-inch}$ offset bowl.
Closet Flange Installation and Wax Ring Compression
Code requires the underside of the closet flange ring (PVC, ABS, or cast iron with a stainless steel collar) to sit directly on top of the finished floor surface. If the flange is buried below new tile layers, an extension kit or extra-thick wax ring with an integrated polyethylene funnel horn is required to guarantee a hermetic seal against sewer gases and flush water.