NCC 2025 Public Comment Draft, Volume 1, Health and Amenity, Part 1 Water Management:

The draft document has some important changes for improving waterproofing and water shedding provisions.

Some of the changes are:

  • Structural falls MUST have a minimum gradient of 1:80 (Exceeding AS4654.2 of 1:100 as DTS)
  • A requirement of a 70mm step down on all structures from inside to outside. Structures also requiring a hob to be installed at the perimeter.
  • Exposed joints MUST be located at the ridge line of falls and must include a hob on either side of the joint. (exposed joints are considered movement joints)
  • Waterproofing membranes MUST be applied to the structural Substrate. That means no screeds or toppings in between the waterproofing membrane and the structural substrate.
  • Floor finishes are to be either self draining or directly fixed to the waterproofing membrane. Which is in turn directly fixed to the substrate. NB: elimination of screed beds and management of subsurface water.

Proposed changes to NCC 2025 for Waterproofing notice

 

ABCB Livable Housing Design Standard:

The VBA have recently published a guide to the NCC Livable housing design standard. Of particular interest to waterproofing is Part 5 – Shower. Part 5.2 requires:

  • At least one shower must have a hob-less and step-free entry. This means the floor level at the entry to the shower recess must be level with the floor outside the recess.
  • A 5mm high lip (such as a water-stop angle) is permitted at the perimeter of the shower recess for water retention purposes. NOTE: AS3740:2021 , 4.8.4 Waterstops for enclosed showers without hobs or step downs states: “(a) where a shower screen is to be installed, a waterstop shall be positioned so that its vertical leg will finish a minimum of 5mm above the finished floor level.

COMMENT: A aluminium angle with a vertical leg 5mm above the finished floor level is a serious trip hazard and likely to cause injury to bare feet, suggest designer specifiers nominate a Performance Solution meeting the NCC objectives referring to the previous AS3740:2010 standard in which the vertical leg is to finish flush with the finished floor level.