In the US and Canada, the standard rough-in for a floor-mounted WC is 12 inches (about 305 mm), measured from the finished wall to the centre of the floor drain. Models for 10 inch and 14 inch rough-ins exist for older or unusual bathrooms.
Europe does not work with one rough-in figure. WC pan connecting dimensions are set out in EN 33, and most new European bathrooms use horizontal outlets, often with wall-hung pans.
How the US rough-in is measured
Rough-in is measured from the finished wall, not from the skirting board or the base trim, to the centre of the closet flange bolts on the floor. A 12 inch rough-in WC is designed so that its outlet sits over that point while the cistern stays clear of the wall.
If a buyer orders a 12 inch model for a 10 inch bathroom, the cistern hits the wall. If the bathroom is 14 inch, a 12 inch WC leaves a visible gap. Most US retail ranges therefore centre on 12 inch, with a smaller choice for 10 and 14 inch.
Certification to ASME A112.19.2/CSA B45.1 is required in the US and Canada, and covers flush performance and other tests. See cUPC and ASME certification.
How Europe handles dimensions
EN 33 (current edition 2019) sets connecting dimensions for WC pans and suites: outlet positions, inlet positions, and fixing dimensions for wall-hung pans and seats. A pan designed to EN 33 should connect to frames and pipework made to the same standard.
For floor-standing pans with a horizontal outlet, the key figure is the outlet height above the floor. For wall-hung pans, the key figures are the stud fixing centres and the inlet and outlet positions relative to the frame. Wall-hung WCs and concealed cisterns explains how these interact.
National habits still matter. Some older European housing has floor outlets, and some markets prefer particular pan heights or projections. Ask local distributors what they stock.
Other markets
Outside the US and Europe, practice varies. Gulf, African and South Asian markets often mix floor and wall outlets, and the floor outlet distance is not always standardised. The best guide is the WCs already sold there and the drawings used by your project customers. S-trap vs P-trap toilets covers the outlet choice itself.
What to put in your order
- The outlet type for every model: floor (S-trap) or horizontal (P-trap).
- The rough-in or outlet height, with tolerance, on the approved drawing.
- For wall-hung pans, the fixing centres and the frame the pan must fit.
- A requirement that inspection measures these on sample pieces before loading.
Next step
If you are adapting a range for a new market, we check the factory's drawings against your market's dimensions and measure samples at inspection. Book a free sourcing review.