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Falls in Wet Areas

Falls in Wet Areas

(a) AS3740-2021 “Waterproofing for domestic wet areas” is a Referenced Standard in the BCA. 

(b) I note section 2.3.2 of AS3740-2021 cites the recommended requirements for falls in the shower recess. At Section 2.3.2 of the Standard, it states that shower shall be 1:80. However, the note at the bottom of the section defers to Appendix B for further information regarding falls in floor finishes.

(c) I refer to Appendix B, Section B1 of AS3740-2021 states that the “primary consideration for falls in floor finishes is to ensure water does not remain on the finished floor in a manner that can adversely affect the health or amenity of the occupants or deteriorate building elements”. 

(d) I note this is written as there may be a variety of reasons as to why a builder cannot achieve 1:80 falls. This is addressed at Section B2 of Appendix B which lists and acknowledges a variety of factors which will affect the falls in floor finishes. This can be seen in the exert below: 

(e) With the above information considered, the standard at Section B3 states that if falls are flatter than 1:100 that that the primary consideration of drainage in floor finishes at Clause B1 is met. 

(f) Therefore, whilst 1:80 is the minimum required fall at Section 2.8.2, the Standard itself through the reference of Appendix B states that primary consideration of falls in floor finishes is to ensure that water does not remain on the finished floor. 

(g) I reference AS 3958.1-2007 “Guide to the installation of Ceramic Tiles” which further addresses falls in ceramic tiles. I refer to Appendix D which states that the recommended fall in a wet area is between 1:80 – 1:100. 

(h) It is noted that the recommended ratio of 1:80 is simply that. A recommendation. The overriding principle to falls in tiled floors is expressed at Appendix D1 of AS3958.1. This clause says: 

(i) From D1 General it can be seen that the primary consideration for falls in floor finishes is to ensure that water does not remain on the finished floor in a manner that:

(1) Adversely affect the health or amenity of the occupants; or 

(2) Causes deterioration to the building elements. 

(j) In summary, even though a shower recess floor may not have a fall of 1:80 or 1:100, the finished floor should meet the performance requirements of Appendix B1 of AS3740-2021 and Appendix D1 of AS 3958.1-2007, being: 

(i) Water does not remain on the finished floor in a manner that can adversely affect the health or amenity of the occupants; or 

(ii) Water does not remain on the finished floor in a manner that will deteriorate building elements; and 

(iii) Water does not pond on the floor, with the exception of residual water remaining to surface tension.