Under the Strata Title Act (Part XV, s58 (a)); the presumption (under the law) is that if the roof leaks in a strata title, upstairs is responsible.

Enforcement of the Strata Title Act is still unproven. Ask the JMB to confirm and make a ruling who is responsible.

Sometimes the owner upstairs is a gentlemen and pays, sometimes upstairs and downstairs share 50:50, other times downstairs pay all.