I would be very surprised if there was not a shared responsibility on the major structural item such as this, if a leaking room causes problems it could affect the whole block! I would suggest that you have a word with either the developer or the company/person you purchased through. If that fails, if you e-mail me, I will suggest the Company I used to purchase my place and whom I trust totally. They also have English speaking staff and would be able to offer advice.
Good Luck
Kevin