WET AREA TIMBER FLOORS NOW AN ALTERNATIVE SOLUTION

23 Nov 2021

After changes to the Building Code were announced by MBIE in November last year, Masterspec invested a considerable amount of time and resources reviewing the changes and updating our libraries. We then published, in May this year, a series of articles addressing the amendments in detail, including those proposed for E3/AS1 and changes concerning the old Amendment 6 Flooring Options.

Previously, Amendment 6 allowed six flooring options, including a few that were no longer in common usage, and we highlighted MBIE’s concern with potential issues in some older timber-based systems. We believe the recent shift away from single storey, single-owner dwellings to multi-unit, medium density construction has been the driving force behind this, with the integrity of the wet-area system and the avoidance of any moisture spills escaping to a neighbouring unit becoming more important than ever.

As of November 5th, we have come to the end of the transition period, with the approved flooring options now retained in the revised E3/AS1 Amendment 7. These include linings and finishes such as

waterproof sheet material (for example, PVC) with sealed joints
ceramic tiles
sealed or polished concrete floors (only slab on grade)

Importantly, the latter's scope is now very limited, defined as "A slab-on-grade concrete floor having a steel trowel or polished finish, sealed at edges where watersplash may occur, when used in a domestic laundry within a garage, or in a building that contains only sanitary facilities".

Timber or timber-based products are no longer included as an acceptable solution. This does not mean that they cannot be specified, merely that the onus is now on the Designer to provide enough performance-based evidence to achieve an Alternative Solution rating for compliance.

There are existing timber overlay and clip-type systems specifically designed for use in these wet areas, and with high-quality surface sealer coatings and sealed joints they can remain durable and impervious to moisture. Systems such as sealed T&G flooring can be shown to historically achieve acceptable performance.

The key to successfully specifying an Alternative Solution is to research well the historical performance of the wet-area system you wish to specify, liaise closely with the supplier of the system to source the latest performance documentation and before applying for Consent consult closely (preferably at a pre-lodgement meeting) with Council as to their expectations and interpretations.

Masterspec’s Guidance notes have been added to a number of existing flooring sections to alert subscribers to particular flooring applications that were previously acceptable solutions, but will now need to be considered as alternative solutions. our Product Partners are working through their system’s compliance pathways and will update as these are completed.

If you’d like a refresher on the changes that became law at the start of November read our article BUILDING CODE UPDATES 2020-2021 - TIME TO ABSORB & APPLY (republished in October NOTES). Contained within are links to articles covering in more detail changes to the various sub-sections of the Building Code.

If you are considering an alternative solution please note the following (from the CoP for Internal Wet-Area Membrane Systems).

Products That Are Not Waterproof Membranes
Where such components or junction details are proposed, consult with a waterproof membrane system supplier for specific recommendations. The following products may be components of or used in conjunction with a waterproof membrane system. They do not have waterproofing properties on their own and are not waterproof membranes:

Sealers, as their films are too thin and are discontinuous
Adhesives, as these are discontinuous
Grouts, as these have no waterproofing capability
Grout sealers, as they rely upon the continuity of the grout
Floor levelling and smoothing compounds as these are porous
Coatings/paints as these are usually permeable decorative coatings, unless it is specifically stated that they are fully waterproof
Concrete treatments such as colloidal silicates

For further guidance the Code of Practice for Internal Wet-area Membrane Systems, of which parts 1-4 form NZBC E3/AS1, is available from the Waterproofing Membrane Association website or free from MBIE's website.

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WET AREA TIMBER FLOORS NOW AN ALTERNATIVE SOLUTION