Dispute with builders over apartment damage

I have an apartment that is just over a year old. Recently had a problem whereby pipe under sink came away causing a lot of damage and the wooden floor will need to be replaced.I had a plumber out that said the pipe was never properly welded and as such is building defect. The management company had said to me builders would cover if it was proved to be defect and i got a report and pictures to back it up . It seems they are now trying to go back on this saying that its outside the 12 month warranty period and that there is no proof that it wasnt welded correctly ,even though i have an independent plumbers report saying that it wasnt. They are also saying something about an indemnity from the plumbers in the first place saying that all pipes were properly fitted correctly on construction(sounds strange to me). Can anyone give advice on what my options are in resolving this.

Were you outside the 12 months when you first reported the problem? Can you claim on the block policy perhaps? Have you shown a copy of the independent report to the management agent? Apologies if you are clear on the difference, but has the management company directors been made aware of the problem? If not, the agent may not be acting on their explicit advice. You can find out who your directors are from the CRO if the management agent is not forthcoming. Sorry about all the questions!

it was about 15 months from taking completion of the apartment. i looked at the block pilocy but have been informed that the excess on the policy is 2500 euro- which is of little help. I havent pursued further with agents but have gone to the building firm direct who said that they would look again and come back to me but wondered if i would have any legal grounds if they again decline to pay out