Joint freeholder query

[Milliebear]

Hi. I wonder if anyone can advise. I live in a flat in a converted house. There are two flats, mine which is ground floor and my neighbours who live in the flat above. We are 50% joint freeholders of the building. I have been living here for aprox 4 years, my upstairs neighbours moved in a year ago.
Shortly after they moved in they found they had a leak in the roof. It turned out that a hip joint on the roof was damaged/missing (apparently it could be seen from the road). They got a quote to get this sorted and have claimed their share from their surveyor who missed it. The surveyor has stated that as I'm a joint freeholder I am responsible for half the costs.
Is this correct? And if so, how would I, as the ground floor flat owner ever be protected please.

[Lawcruncher]

It depends on what the leases say about repairing the area in question and who pays for it.

[Milliebear]

Yes, thought as much. The repairs are split 50/50. I should have had my own survey done of the roof when I bought the groundfloor flat. It's the first flat I've bought so I didn't realise the pitfalls. Thanks for your reply.