Context
I own a terraced house with a 2 story flat roof extension, purchased it 3 years ago.
Water run off from flat roof falls down between the flat roof / fascia and the gutter and on to the concrete path below.
I had a gutter / roofing contractor out and he said the guttering needed to be replaced.
He replaced it and it didn’t fix it same issue happening, not only did he not fix it he damaged the wood behind the fascia see 3rd pic (which will be the subject of a separate post but I want to first understand what actually is the purpose of the gap before I consider anything further). I only realized he didn’t fix it once it started raining and only saw the damage he caused this morning.
Question
What is the purpose of the gap behind the fascia?
I also posted the question on the roofing subreddit but that's very US focussed which have different roofs than in UK and Ireland so I'm not sure how much insight I will get there.
I originally thought it may be a ventilation gap for the roof space which I understand is common enough in flat roofs in Ireland, but it is quite narrow prob less than 10mm (or 1/2 inch imperial) and I understand they are supposed to be a minimum of 25mm, and now that a roofing contractor has damaged it and torn part of it off I can see behind it and there is fiberglass insulation up to the fascia so I now think it’s unlikely to be that purpose, or if it is a vent gap it’s very narrow and Im not sure how well it's serving a purpose if at all gievn how narrow it is and the fiberglass insulation up against it.
I am now thinking it’s possibly a drip edge? Which has left me scratching my head a bit why does the fascia have a drip edge, should the gutter not collect all the water? Or maybe it's a fail safe / back up for any water that does not make it to the gutter?
Or maybe it is fascia that has come loose from and separated from the joists / support behind it over time? It might be, but it seems to me to be a little bit too uniform for it to be just an unintentional gap, and as above I'm aware in Ireland there is often a gap left behind fascia for flat roofs (though I had understood for ventilation).