Bathrooms and Laundry’s are the wettest rooms in the house which if not waterproofed correctly will cause structural damage. Statistics indicate the average age of a bathroom is around 10 years before being renovated. One of the most commonly changed rooms in the house. Fortunately the Australian Standards AS 3740 apply to waterproof these areas. Both application and membrane products should comply with Australian Standards. The following information is designed for practical advice:

New Construction bathroom waterproofing membrane  bathroom waterproofing membrane Shower Repairs


Building code compliance refers to the National Construction Code (NCC) objectives with either Deemed-to-Satisfy Solutions (Australian Standard AS3740) or a Performance Solution authorized by the Registered Building Surveyor (under State legislation).

Both NCC Volume 1 & 2 have the same reference with details explained in AS3740. The Bathroom requirements include substrate conditions and cover options of design including; Showers with hobs, Hobless Showers (walk in), Bath Showers and Disables Showers the former two are most popular.

Showers with Hob

AS 3740: 2010     3.13.3  Hob Construction (Showers)

This clause nominates that the substrate for hobs must be constructed from masonry, concrete, corrosion-resistant metal or similar material. Autoclaved aerated concrete may be used for internal membrane systems, but not for external membrane systems. When autoclaved aerated concrete are used, priming the surface is required prior to membrane application. All gaps, joints and intersections of the hob substrate are to be made flush before membrane application. The hobs must be adequately secured to the floor, plus sealed to the wall prior to internal membrane application.

Work from the substrate up, determine the condition of the slab or sheeting over timber structure as to the presence of water trapped. If in doubt apply a vapour barrier coating. When planning the job anticipate that building movement will occur and therefore to secure all wall/floor joints, drains, hobs, sheet joints and movement joints. We recommend liquid applied membrane systems for the Australian climate as the most practical and economic products for a secure job.

BATHROOM INSTRUCTIONS – Waterproofing Showers with Hob   

Hobless Showers

AS 3740: 2010        3.13.5 Unenclosed Showers

This Clause sets out requirements for two types of unenclosed showers, as follows.

  1. Type 1; unenclosed shower has a device that will restrict splashing during use. A waterstop shall be placed under the device and across the opening of the shower screen.
  2. Type 2; unenclosed shower which does not have a device that will restrict splashing (as with people with disabilities). The water stop shall be a distance of a minimum of 1500mm from the wall connection of the shower rose.

BATHROOM INSTRUCTIONS – Waterproofing Hobless Showers

Key Products:

YouTube video – Bond Breaker System – Class II Membranes


For both hob or step-down showers if leaking is a major problem, treat the project ‘as new construction’, pull out the existing shower and start again. However, for minor repairs, pull out any silicon and replace joint sealing with polyurethane. Limit the water penetration by applying a water repellent over the tile grout lines and tiles. Ensure the exit drain is waterproofed. In more extreme cases cover tiles and use a trafficable polyurethane floor.

Key Products:

Reference information:

Diagrams care of MBA NSW and other sources (jpeg diagrams)
Youtube video – Bond Breaker System- Class II Membranes

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