"In regards to the compulsory guarantee from the developers, would anybody know who is responsible for holding this? We look after houses on a few developments that are all suffering the same damp problem (caused by building defects), owners are asking us to help, but if developers have 'dissapeared' where could we get hold of this guarantee?
They have insurance policies, details of which should have been passed to the original buyer of the property. It should be attached to your escritura/title deed, so check with whoever holds that. Howeveer, most policies are just for structural failure and that is only the concrete foundations, pillars and floors. The walls can fall out and they are not covered as they are not structural. Check with the Community insurance policy. Also try chasing the architect as they have liability for at least 10 years too. The Architecto Técnico was also responsible for supervising the construction on behalf of the developer ir he was not also the building contractor. So you have the promotor, the building contactor, the architect, the architecto técnico, the community insurance company and your own insurance company.
However, sometimes its cheaper in the long run just to pay for the defects repair yourself. Life is short and do you need to spend all your time hassling. may be difficult to swallow, but it lets you get on. Make sure that you have a professional look at the problem so that there is a formal report.