Leaky roof

[Windswept]

Greetings. Another of those long-time lurkers here. We have a stone & rubble built semi built around 1860, with later additions. It was converted long ago from a larger house. The immediate problem is not really ‘period’, being a small flat roof on a lobby that joins the old and new blocks. It has started to leak, as they do, the leak exiting rather alarmingly through a light fitting. This happened during storm Darragh, dried up over the past rain-free week, and has started again as the weather returns to normal. There are a couple of small stains developing on the plasterboard ceiling but no sign of sagging or mushiness.

Plan A was simply to paint a suitable acrylic gunk onto the surface and see what happens - roofers seem to be on their hols or otherwise unavailable atm anyway. The trouble is that we / our handyman can’t see any obvious damage to the roof surface other than a bit of algae. Next step will have to involve someone going up a ladder in the rain to have another look. Tempted to push a screwdriver through the ceiling…

In the meantime can anyone spot anything from the attached photos? There are three roofs and two valleys draining onto this roof, which in these parts means a lot of water. The block on the left is a modern concerete block extension, the other two sides are the original building ( felt under the slates, probably re-roofed around 1960).

Do we need a plan B?

 

[Robola]

Water can track a long way from the point of entry. My money is on something to do with that valley, it looks to be flat flashing under the slates, what's to stop water tracking behind the slates? The bottom 2 on the right have slipped into the valley, also subject to previous repair including some kind of gunk. I've also found that the movement of lead due to thermal expansion can wear through points in contact with weaker materials.

 

[Cubist]

Given that roofing felt has a potential maximum life expectancy of 10-30 years then your roof has probably seen its day. Plan B would be to replace it all but in the meantime a strategic application of a suitable gunk might tide you over. You might consider shoving a borescope up through the plasterboard below to gain an understanding of the source of the water to aid selection of the 'strategic' gunk applications. One further, though perhaps an unhelpful point though right now, is that old felt roofs don't like being walked on.

 

[CliffordPope]

What's happening up at the top of the gulley between the two sloping roofs, by the chimney? In the photo it looks as though it just stops - is it in fact tucked well up under the ridge tiles, or can water running down the chimney just run straight under the lead?