neverquirefinished

I did consider condensation. the initial leak was almost certainly rainwater ingress. It leaked in every time it rained. The leak IS in the bathroom, which has very little in the way of ventilation - although this was never a problem - no damp/mould etc. With regards to GRP, I doubt that is an option. Every house i have seen of this build type has a bitumen and felt roof construction. It's a shame I can't find a build diagram or spec - I'm having to assume that there is a series of waterproof layers. The roof is cast concrete panels, 7 I believe, which span the entire width of the house. I have to presume that these are bitumened in the joints from the top, then a 1st waterproof layer, before timber/insulation and then the top covering of felt which is visible. I guess I can pay a roofer to come and prove my theory - First a flood test to prove its watertight, then once its drained, have him cut a section of felt out above the leak, and check if the layers below are sodden?

Property is a 1950's pre-cast concrete mid-terrace house, with a flat roof. All walls/floors/ceilings are cast concrete. The roof covering is around 15 years old, and appears to be in fairly good condition. It is of a torched felt construction, with (I assume) timber cavity underneath, with some form of insulation. First leak was several months ago, I had a look, and noted a few small areas of cracking around a drainaway. Roofer came out and laid around 1m2 of torchon. Leak vanished over night. Perfect. Ceiling coverings replaced. Fast forward a few months, and its leaking again. Yet, and this bit hurts my brain......It only tends to leak into the property when it is DRY/fair/warm outside. We had a week of rainstorms, and not a single drip came in. yet it was nice and sunny, around 14 degrees a few days ago, and it was dripping every few minutes. Is it possible that this current ingress of water is simply water that is 'stored' in the insulation, following the first leak? If that IS the case, I'm assuming I am looking at a full strip and re-laying of all wood/insulation/membranes?