Many of the enquiries received through the KBDi Technical Support enquiry form relate to waterproofing requirements in bathrooms. Relatively recent changes to the NCC mean more care is required in the design phase of a bathroom; decisions made in the planning phase can significantly impact waterproofing requirements.
Bathroom designers must carefully consider:
- the type of shower design (i.e. enclosed or unenclosed)
- the practicality of placement of drainage relative to the shower and general wet area
- the inclusion of voluntary drainage and its impact on falls
- tile dimensions (and control of gradients), and
- finished heights at doorways
The location of waterstops is dependent on or impacts the above. In this feature, we’re focusing on this component and sharing some basic considerations for designers.
What is a waterstop?
Australian Standard AS3740: 2021 defines a waterstop as a:
vertical extension of the waterproofing system forming a barrier to prevent the passage of moisture in the floor or vertically in a wall
A waterstop (also known as a water bar) must be installed to retain water within the shower or wet area. They’re an integral part of the waterproofing system and must conform with AS3740 clauses 4.8 (for shower areas) and 4.9 (for door openings).
The type of shower (i.e. enclosed or unenclosed) will determine the requirements.
Unenclosed Showers
The Standard defines two types of unenclosed showers:
Type 1 unenclosed showers ‘have a device that will restrict splashing during use’. This could be a frameless shower screen or a shower over a bath with up to 900 mm fixed glass screen.
Type 2 unenclosed showers may include shower areas with or without curtains, a shower over a bath with a curtain, or – as is more commonly the case for our members – an area where a shower screen partitions one side of the shower, the entry to the shower is open, and the spray from the rose can still exit the shower past the screen 1500 mm.
The Standard states that an unenclosed shower shall incorporate a waterstop finishing at the perimeter of the shower area.
A Type 1 unenclosed shower must have a waterstop placed under the splash restriction device and across the opening of the shower of a Type 1 shower screen.
A Type 2 unenclosed shower requires that a waterstop be installed a minimum of 1500 mm from the shower rose connection to the wall or the ceiling.
Importantly, for both Type 1 and Type 2 unenclosed showers, the Standard states that:
The waterstop shall have the vertical leg finish flush with the finished surface of the floor and, where the waterstop intersects with or joins a wall, the junction shall be waterproof.
Enclosed Showers
The Standard requires enclosed showers to have a waterstop installed under the bottom rail of the shower screen and the opening. Where there is no hob or set-down, AS3740 states that at the extremity of the shower area:
Where a shower screen is to be installed, a waterstop shall be positioned so that its vertical leg will finish a minimum of 5 mm above the finished floor level.
Design Considerations
By carefully planning waterstop placement, bathroom designers not only help their builders meet compliance standards. They also create safe, functional, and long-lasting spaces for clients without awkward aesthetic compromises.
Following are four key points to keep in mind.
#1 Tile Transitions
The waterstop typically creates a defined edge between wet and dry areas. Designers should aim to align the waterstop with tile joints or grout lines; misaligned positioning can disrupt the flow of the tile pattern, leading to an uneven appearance and unwanted visual distraction.
#2 Tile Cuts and Wastage
If the waterstop is positioned without considering the tile layout, it may require numerous small or irregular tile cuts. This not only affects the aesthetics but can also increase material wastage and labour costs.
#3 Floor Falls and Drainage
The floor in the wet area will need to meet the Standard’s requirements for falls to waste. The waterstop should be positioned to accommodate this fall without creating an awkward transition in the tile pattern.
#4 Tile Thickness
As indicated above, in open (or unenclosed) shower areas, waterstops must be installed flush with the tile surface, so the thickness of the tiles used in wet and dry areas should be considered.
In summary, all bathroom designers should always:
- Plan Ahead and Lock in Design Decisions: consider all of the above and liaise frankly with your client from the outset.
- Prepare a Tile Layout Plan: Use a tile layout plan to illustrate how the tiles will meet the waterstop.
- Collaborate with Trades: As we always say here at KBDi, good relationships with reliable tradies are invaluable. Liaise with reputable waterproofers and tilers early in the design stages to ensure your plan can be practically executed.
Have you used the KBDi Technical Support Service yet? You can learn more about this member-exclusive function here.