What BCA gave are just guidelines on how to deal with interfloor leaks. It is not a rule or regulation. The cost bearing will still have to depend on the actual cause of the leak. For example, if it is found the leak is caused by the concealed pipes of the lower unit running along the ceiling, then, there is no reason for the upper unit to bear the cost of the repair and vice versa.
The agreement should be divided into 2 parts, the detection of leak and the repair of leak. Both upper and lower unit should work together to engage the specialist to do the detection first. The repair of leak will come after.
Usually, the lower unit should not have any drain pipe concealed in the ceiling if a leak is found in the ceiling. Turning of the water supply in the lower unit will confirm this .
Hi according to the BCA website, the Building maintenance and strata management act is a ruling as it is a statute and legislation administered by BCA, they are not just guidelines. See the below extract:
"The Building Maintenance and Strata Management Act (BMSMA) and its subsidiary legislations, except the provisions on stage development, came into operation on 1st April 2005. The provisions on staged development will come into force on a date to be announced. The BMSMA comes under the purview of the Ministry of National Development (MND).
The legislation is administered by the Commissioner of Buildings (COB) of the Building and Construction Authority (BCA).
The BMSMA is a statute merging the Buildings and Common Property (Maintenance and Management) Act [“BCPA”] with parts of the Land Titles (Strata) Act [“LTSA”]. It is the result of an extensive consultation process with the industry and the public culminating with a Select Committee review. The BCPA has been repealed. The LTSA has been amended and continues to be under the purview of Ministry of Law (MinLaw). However, the Strata Titles Boards (STB), which is provided for in the BMSMA, now comes under the ambit of MND.
There are
a number of significant changes introduced in the BMSMA. They include, among other things, 2-tier MC scheme, proportional representation in the council for multiple lot owners, responsibility of owners to maintain their windows,
presumption of liabilty on upper floor unit owners in leakages between units, office bearers permitted to resign without replacements and provision for share values to be varied in staged developments."
http://www.bca.gov.sg/BMSM/bmsma.html