Be alert, not awash!
John Rathbone, part of the committee working on Australian Standards for Waterproofing, talks about the new requirements for rimless and stand-alone baths.
New Zealand was the first country in our area to strike problems with rimless and stand-alone baths. The first wave of imports were “budget baths” which could be produced cheaply as rimless. They are less complex moulds than standard baths and were installed against the wall sheets with the shower over the bath. Problems soon became apparent: water from the shower rose penetrated the junction between the wall sheet and the bath, damaging the bathroom wall and floor. Various “band-aid” solutions were tried without success. This led to the Standards Australia Waterproofing Committee introducing a new procedure in the 2010 edition of AS 3740 to address this type of bath, then marketed in Australia. However, many new types of rimless and free standing baths have since come onto the market. Many are installed under showers, with resulting damage to the bathroom floor and water penetration to adjacent rooms. The Committee has addressed this latest problem in AS 3740 amendment one (reissued 12/12/2012) which will be referenced in table 188.8.131.52 in the National Construction Code (NCC) 2013 edition. The NCC is released annually on 1 May.
The new requirements for rimless and free-standing baths where there is a shower fitted above the bath are as follows: For both types the floor of the bathroom must be waterproofed and drained to a waste.
A rimless bath with shower over is treated as a type two shower. The water stop to the floor shall be a minimum of 1500 mm from the wall connection of a shower rose and must finish flush with the finished surface of the floor. (Rarely used method).
Waterproof the whole bathroom floor, including water stop in the bathroom doorway. (Common solution).
Australia can avoid the expensive experience of New Zealand simply by following the new requirements of AS 3740 and by always using a professional to install the waterproofing.
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