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Walk-In Shower Calculator — Screen, Drain & Tanking
Calculate glass screen dimensions, channel drain length, tanking area, fall distance and seal requirements for a walk-in shower installation.
Width of the shower area
Depth from back wall to screen
Standard: 1950-2000mm
Tank to full ceiling height ideally
Glass screen with fixings
Linear or point drain unit
Per m² of membrane applied
Enter the X in 1:X. Standard 1:80 for wet rooms (LABC: 1:80 to 1:100)
Extra seal length for waste/overlap
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How We Calculate This
This calculator sizes the glass screen, determines drain configuration, calculates tanking area and works out the floor fall for a walk-in shower.
The formula
Screen area = (Opening width − 20mm) × Screen height
Fall distance = Fall run ÷ Fall ratio (1:80)— the fall run is the full shower depth for a back-wall linear channel, or the drain-to-furthest-edge distance (about half the depth) for a centred point drain.
Tanking area = Floor area + (Sum of wetted wall lengths × tanking height)— for a back-into-the-corner walk-in this is the back wall (opening width) plus the two side returns (shower depth each), in line with BS 5385-4 wet-area practice.
For a 1200mm × 900mm walk-in shower with a 2000mm screen and 2400mm tanking height: glass = 1.18 × 2.0 = 2.36 m². Fall (linear) = 900 ÷ 80 = 11.3mm. Linear drain ≈ 1100mm. Tanking = (1.2 × 0.9) + ((1.2 + 2 × 0.9) × 2.4) = 1.08 + 7.20 = 8.28 m².
Glass specifications
- 8mm: Suitable for screens up to 800mm wide, lighter weight (~20 kg/m²)
- 10mm: Recommended for all walk-in screens, better stability (~25 kg/m²)
- All glass must be toughened safety glass to BS EN 12150
- Anti-limescale coatings (e.g. Easy Clean) are recommended for reduced maintenance
Frequently Asked Questions
The minimum recommended screen width for a walk-in shower is 700mm to prevent excessive water spray. Most walk-in screens are 800-1200mm wide. The screen should be at least as wide as the shower head spray pattern. For comfortable access — and to keep water contained — allow an entry gap of at least 500-600mm between the screen edge and the opposite wall (700-800mm is more comfortable; openings below ~550mm feel cramped). Accessible/Part M wheelchair-friendly showers need a wider clear opening still. Standard UK stock sizes are 700, 800, 900, 1000, 1100 and 1200mm.
10mm toughened safety glass is the recommended choice for walk-in shower screens. It is more rigid, feels more substantial, and is less likely to flex or vibrate. 8mm glass is acceptable for smaller screens (up to 800mm wide) or where the screen is supported on both sides. All shower glass must be toughened safety glass conforming to BS EN 12150. Larger screens (over 1000mm) should always use 10mm glass.
Walk-in showers can use either a low-profile tray or a fully tiled wet room floor. A tray is simpler to install and waterproof but limits design options. A wet room floor (using a former and tanking system) gives a seamless, level-access finish but requires more careful installation. Both approaches need proper waterproofing (tanking) of the surrounding walls.
A linear (channel) drain along one wall is the best choice for walk-in showers. It allows the floor to fall in one direction only, simplifying installation. Linear drains also tend to clear water faster than point drains: a standard residential channel on a 50mm (2in) waste typically clears around 30-40 L/min, with high-flow units on a 75mm (3in) waste reaching 60-90 L/min — always check the manufacturer datasheet for the rated flow. They create a clean, modern look. Point drains work but require a four-way fall which is harder to tile.
All walls within the shower area should be tanked to full height (floor to ceiling). The floor must also be fully tanked. Beyond the shower screen, tank at least 300mm past the screen edge on adjacent walls. Use a liquid membrane (2 coats) or sheet membrane with taped joints. Pre-formed corners and drain collars are essential for a watertight system.
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Last updated: June 2026
Verified against UK standards · estimates only, confirm with your supplier.