Bathrooms feature prominently in renovation and home building considerations.

A major concern with bathrooms and all wet areas is the efficiency of the floor drainage.

There is wide choice of grates, offering many shapes, sizes and designs.

Lineal grates have become popular as an alternative to the traditional round or square relatively small grates.

The open flowing design of modern bathrooms is a major driver in demand for linear grate and channel systems.

A thin long shower grate, like Stripgrate, performs better than a small round or square shower grate and is less prone to blocking.

The performance or style of a particular long drainage grate, may not suit as a shower drainage grate. Likewise a balcony grate needs to meet different requirements to a shower grate or bathroom floor grate.

Plumbing fixtures should meet appropriate authority standards. The Australian Watermark licensing system gives the public assurance that bathroom or shower grates that have Watermark approval have been tested and proven reliable.

AS 3740—2004 is currently under review to ensure it reflects current best practice.

The standard says that a waterproof membrane terminating at or in the drainage flange can be either over or underneath the tile bed (screed).

The most common practice nationally is to apply a membrane under the screed.

Problems associated with under screed waterproof membranes.
Water travels through grout joints and through cement based screeds and in a perfect world where the floor the screed is over, whether it is concrete or timber, is level, most of the water will find its way to the drain, however even under perfect circumstances the screed will remain permanently wet if below screed waterproofing alone is installed.

In too many instances the floor below the screed has depressions or even falls away from the drain that cause pooling of water beneath the screed, and/or the drainage flange is fixed to the top of the floor as per AS 3740—2004, section 5.12.1, Fig. F10, with the combined thickness of the flange itself and the covering membrane making it an effective dam wall, again pooling water beneath the screed.

It is unacceptable that with even the best conditions, the screed in a regularly used shower with a tiled floor remains continually wet, soaked with water carrying detergents and body fats etc.

Conclusion
Under screed waterproofing alone is unsatisfactory. A better option is to waterproof both under and over the screed, which allows for the possibility that an over screed membrane may be punctured before tiling is finished.