When is a floor waste required in a bathroom? Explained.

A floor waste is a drainage point set into your bathroom floor that captures water overflow, but not every bathroom needs one. Whether you require a floor waste depends on your bathroom type, waterproofing requirements, and compliance with the National Construction Code (NCC).

What is a floor waste?

A floor waste (sometimes called a floor drain) is a small drain in the floor, usually in the corner or centre of a bathroom or laundry. It’s designed to catch any excess water that escapes from showers, sinks, baths, or other fittings, and helps avoid unwanted puddles or worse, water damage.It’s not always about cleaning up spills either, in some homes, plumbing fixtures are designed to drain to the floor waste as part of the water management plan.

Do you have to have a floor waste in Australia?

That depends on your bathroom setup and the type of home you're in. According to the National Construction Code (NCC) and AS4370-2021, here’s the general rule: You need a floor waste in bathrooms and laundries in Class 2, 3, or 4 buildings (such as apartments, hotels, and some multi-unit townhouses), especially when there's no built-in overflow in fixtures like the bath or basin. But for standalone homes (Class 1), it’s a bit more flexible. You might not need a floor waste if all your plumbing fixtures have proper overflow protection (like an overflow hole in the basin or bath) and the bathroom is designed to contain water.

Building code recap

• Apartment / multi-dwelling: Yes (usually), Especially if no built-in overflows on fixtures

  
  

• Freestanding homes (Class 1): Not always, depending on layout and drainage design

  
  

• Bathroom with hobless shower: Often required.

  
  

  Building Class Requirements

  • BCA Class 2, 3, and 4 Buildings (Apartments, Hotels, Townhouses above others): The National Construction Code (NCC) strictly mandates a floor waste gully in bathrooms located above another sole-occupancy unit or public space to prevent overflow damage to property below. If fixtures like baths or basins lack built-in overflows, or if the shower layout causes the wet area to bleed into the general floor space without containment, a dedicated room floor waste is typically triggered.

    
    

  • BCA Class 1a Buildings (Standalone Single Houses): The NCC Deemed-to-Satisfy provisions do not universally force a general second floor waste outside of the shower recess itself in single-family standalone homes, provided fixtures have proper overflow protection and the room is designed to contain water.

    
    

  • BCA Class 1b Buildings: The NCC allows for open wet rooms but the entire floor area requires waterproofing amongst other design parameters.

    
    

  Hobless & Step-Free Implications

  • Waterproofing & Graded Falls: A hobless/step-free shower requires proper gradients (typically a continuous fall between 1:80 and 1:50 to the waste under NCC rules).

    
    

  • Whole Room Waterproofing: Because a hobless shower lacks a physical hob or step-down to contain water, if water can migrate past the immediate shower zone into the main bathroom floor, the entire bathroom floor may need to be treated as a wet area, waterproofed, and graded toward a functional waste.

  
  

• Laundry: Yes, floor waste required in most builds

Always check with your building certifier, plumber or builder to make sure you’re ticking all the boxes for your build type.

Why you might still want a floor waste

Even if you’re not technically required to have one, there are a few reasons why you might still want to include a floor waste:

• Peace of mind - especially if you’ve got kids who treat the bathroom like a splash park

  
  

• Walk-in or open showers - where water can spread across the floor more easily

  
  

• Easier to clean - you can hose down or mop the floor without worrying

  
  

• No built-in overflow in your fixtures - like some freestanding baths or wall-hung basins

The Hidden Rule: The "Voluntary Waste" Trap

A major reason modern builders actively avoid installing floor wastes unless legally required comes down to mandatory floor grading rules introduced in the NCC 2022 guidelines

• The Rule: If a floor waste is present in the main bathroom floor, the builder must legally slope the entire room's tiling toward that drain with a fall between 1:80 and 1:50

  
  

• The Impact: Grading an entire large bathroom floor complicates tile installation, requires expensive sub-floor screeding, and can cause large-format tiles to look uneven or cracked (lippage)

  
  

• The Result: Omitting the drain allows the builder to lay a completely flat floor outside of the shower stall, saving time and achieving a cleaner, ultra-modern aesthetic

When you might not need one

You can potentially skip a floor waste if:

• Your bathroom fixtures all have built-in overflows

• The floor is fully waterproofed and contained, with no risk of water spilling out

• You’re in a freestanding house, and your builder signs off on the design

  
  

  But again, check with your building certifier to ensure compliance with the NCC and AS3740, including plumber and builder’s advice. Some councils or certifiers may still prefer (or require) one just to be safe.

How to Proceed Safely

Before finalising your architectural plans or signing off on your plumbing layout:

1. Review the official compliance framework via the Australian Building Codes Board (ABCB) NCC Portal to confirm current wet area guidelines

   
   

2. Request a formal assessment from your plumber regarding your fixtures, ensuring your selected basins match compliance rules on The Blue Space Basin Guide

   
   

3. Ensure your builder documents the exact waterproofing boundary and doorway water-stop details in writing

4. Building surveyor to confirm compliance with NCC and AS3740

Superstruct Building Surveyors | Australia