Updates to ceramic tile standard AS 3958:2023

The standard is not a mandatory obligation as a primary reference document in Schedule 2 of the NCC.  However, NCC primary reference AS 3740:2021 Waterproofing of domestic wet areas refers to the previous edition of Part 1 (2007) in its informative content. Some Guidelines to Standards and Tolerances also make a reference to AS 3958 without a specific year or edition. 

The revised standard provides installation requirements for internal and external tiling work for ceramic and stone tiles. This includes mosaic tiles and large panels. It provides details on the preparation of backgrounds, bonded fixing, grouting, and maintenance of tiled surfaces. 

The standard also addresses applications such as swimming pools, floor gradients, screeds, and rendering.

Some of the key changes to the standard include:  

• Guidance on preparing substrates for tiling 
• Instructions for bonded fixing and grouting, including greater detail on adhesive types 
• Coverage of floor and wall tiles, including mosaics and panels 
• Recommendations for cleaning and maintenance 
• Notes on specialised applications like swimming pools and floor gradients. 

Installation advice 

A key update relates to installation practices when adhering tiles. Section 5.6 provides detailed information on fixing methods for tiling systems where manufacturer’s specifications have not been provided. 

Suitable methods it recommends for fixing include: 

• Notched trowel method 
• Floating method (only for thin-bed fixing)  
• Buttering method.  

For all the above methods, the adhesive is to be applied evenly over the entire tile. 

The buttering method is more suitable for awkward tiling positions such as around window openings. It involves buttering or applying adhesive to individual tiles.  

The previous version of the standard (AS 3958.1:2007) stated that some manufacturers did not recommend buttering, yet when applied with a suitable notch trowel the standard indicated this was generally considered acceptable provided adequate coverage was obtained.

It further stated that spot-fixing of tiles with four or five ‘dabs’ of adhesive is not recommended and should be avoided at all times. 

The new standard permits the use of ‘spot bonding’ (new terminology) with reaction resin adhesives provided it is carried out according to manufacturers’ instruction and where manufacturers’ adhesive contact coverage and adhesive bed thickness requirements are achieved.

Adhesive coverage and distribution

Clause 5.6.5.1 provides the details for the coverage, distribution and depth of the adhesive coverage which is specified in Table 5.6.5.2. Depending on the location of the tiles, the minimum coverage can range from 65% for internal residential walls, to 80% in residential floors and 90% for wet areas. 

The adhesive should be evenly distributed and of uniform depth to provide support to the tile body, with full support to tile perimeters. This will reduce stress on the tiles. The manufacturer’s instructions regarding the depth of the adhesive should always be followed.

Compatibility 

It is important that the adhesives used are compatible with the background (substrate), waterproof membrane and tile that they are being applied to. Advice should be sought from the adhesive manufacturer to determine compatibility.

A lack of compatibility between materials or inadequate bedding can create voids behind tiles and between substrates. In some cases, a lack of support can lead to drumming or hollow walking surfaces, cracking of tiles or lifting of tiles, leading to costly rework and disputes. 

Selection of Adhesives

The selection of adhesives will depend on several factors: Application/location, service requirements, type of tiles, substrate, and site conditions. Here is a general overview of the different types of adhesives: 

Cementitious-based adhesives  

Usually applied to concrete, brickwork, plywood, plasterboard and fibre cement sheeting substrates. They provide resistance to environmental stress, including UV exposure and temperature fluctuations. 

Resin adhesives

Unlike cementitious adhesives, they do not rely on evaporation to cure. This makes them ideal for dense, non-porous tiles (like porcelain) or critical exterior areas like swimming pools and facades. 

Reaction resin adhesives (or reactive adhesives)  

High-performance, two-component (epoxy, PUR) or curing-agent systems that harden via chemical reaction rather than solvent evaporation. This forms exceptionally strong, durable, and chemical-resistant bonds.

Always check the manufacturers’ recommendations before using its products to confirm suitability for interior and exterior tiling, walls, floors or both.   

The above is intended to provide general information in summary form. The content does not constitute specific advice and should not be relied upon as such. Formal advice should be sought by members and customers with respect to particular matters before taking action.