We are often asked why the building code doesn't explain in details how buildings are to be constructed (ie how to install ceramic floor tiles to prevent water escaping?).
Simply put the Building Code of Australia (also known as the National Construction Code - or N.C.C) is a performance based list of requirements which does not contain a lot of specific information on HOW to achieve those performance requirements. The expected performance is based on the probability that something untoward may occur as the result of the building work not being undertaken in a proper and tradesman like manner. To establish the method for writing an expert witness report I will use the example of water ponding on a shower recess floor, creating a slip hazard.
The Building Code of Australia states:
"O2.2
The Objective is to—
(a) safeguard occupants from illness or injury and protect the building from damage caused by—
(i) surface water; and
(ii) external moisture entering a building; and
(iii) the accumulation of internal moisture in a building; and
(iv) discharge of swimming pool waste water; and
(b) protect other property from damage caused by—
i) redirected surface water; and
(ii) the discharge of swimming pool waste water"
This really just means that the tiles must be laid so that nobody gets hurt and no property is damaged as a result of the installation.
You will note that at this stage we only know that there is a defect because water is ponding or pooling on the floor. We know that the BCA states that this should not occur, but we have no idea what may have been done differently.
To do this we look at the Australian Standard for Waterproofing. Compliance with The Australian Standard is not necessarily a mandatory requirement but we can learn what is an industry accepted method of achieving compliance with the BCA (which is itself a mandatory requirement)
The standard states:
“3.4 Shower Floors
Falls in shower floors shall be sufficient to prevent—
(a) surface water from being retained on the shower floor (except for residual water remaining due to surface tension); and
(b) water from discharging outside the shower area..”
So now we know that the water is ponding on the shower floor which is a slip hazard - contrary to the requirements of the BCA and we know what could have been done to ensure that the tiles were not installed as a slip hazard. In this way we have established what is defective, why it is considered defective, and what should have been done in the first place. This is the format of an SHS expert opinion report which may be used at the Building Commission of Western Australia.
