How Much Shower Tray Fall Do I Need?

How We Calculated This

The fall ensures water drains towards the waste outlet and does not pool:

• Minimum gradient: 1:80 (12.5mm per 1,000mm)
• 900mm tray: 900 / 80 = 11.25mm, say 11mm
• 1,200mm tray: 1,200 / 80 = 15mm

Fall Requirements by Application

• Pre-formed shower trays: Fall is built in — just level the tray
• Wet room (tiled floor): 1:80 minimum fall to linear or point drain
• Walk-in shower: 1:60 to 1:80 depending on flow rate
• Balcony/terrace: 1:60 minimum for external drainage

Wet Room Specifics

For a wet room, the fall is created using a pre-formed gradient tray (former) or by building up the screed to the correct gradient. The drain position determines the fall direction — a central drain needs a four-way fall, while a linear drain along one wall needs a single-direction fall.

Building Regulations

Approved Document H requires adequate drainage to prevent pooling. While it does not specify an exact gradient for shower trays, BS 8000 and manufacturer guidance recommend a minimum 1:80 fall. Wet rooms should also comply with BS 5385 for tiling and waterproofing standards.

Tips

Use a spirit level and straight edge to check the fall. For wet rooms, consider a proprietary gradient board system rather than building up screed manually — it’s faster, more accurate, and guaranteed to meet the correct fall.