Fall
Fall is the slope built into a wet area floor or surface to drain water toward the outlet. NCC 2022 requires 1:80 minimum to 1:50 maximum in shower floors.
Ask Chalkline about this →Fall (also called gradient or slope) is the slope built into a floor, roof, or surface so that water drains toward an outlet rather than ponding. On wet area floors, fall is expressed as a ratio: 1:80 means the floor drops 1 mm vertically for every 80 mm horizontal.
Under NCC 2022 Housing Provisions Part 10.2.12, shower floors must have a minimum continuous fall of 1:80 and a maximum of 1:50 toward the drain. Too shallow (less than 1:80) causes ponding and accelerates mould growth. Too steep (more than 1:50) is uncomfortable underfoot and can cause tiles to slide during installation.
Fall is set in the tile bed (or screed) and must be maintained uniformly across the floor. It is checked by the tiler before fixing tiles and confirmed visually at PCI by running water from the shower rose.
Also known as: gradient, slope, drainage fall.
Category: On-site.
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Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency.