Help can anyone give ideas what this leak is?

[MissOldCadburys]

So we have contacted builders insurance and they said the will ring us today to schedule a date to come and check this out (not sure if we need an emergency plumber).
We spotted this on Friday it definitely is quite recent as it wasn't there before. It has been raining very heavily where we are the past few weeks so don't know if a leaky pipe or gutter issue.
The wall is wet so it's still leaking whatever is causing the problem. Also paint is coming off and it's just getting worse.
It's an external wall next to neighbours and part of an old extension (only recently moved in).
Help!

I'd say pointing somewhere. Powerful rainfall hammering against an external wall with weak pointing?

Thank you for the suggestion I haven't even thought of that. We have had extremely heavy rain. Will add it to the list of things to check.
The house is an older house so could be.

It would help to see a picture of the external wall.

What is above it?

Is there a flat roof?

Post photos of the roof, downpipes, gutters, and joint of extension to original

I tried my best, the wall leads down a narrow alley between our house and neighbours.. I can't see anything if note.

The extension roof itself is flat, the Gutters themselves look the same going the way around the house but I can't see above them. Top of the roof of the original house is pointed.
Starting to think it's a burst pipe somewhere.

Water is a
Nightmare as it doesn't always show up at the point of entry. We had a tiny shift in 1 roof tile that caused water marks around one of our windows downstairs, no issues upstairs - so don't just check immediate areas for brick work, flashing or roof times etc

Water is seeping through the waterproof membrane. A water leak will always find a way in if water proofing fails. Water doesn’t need much of a gap to trickle through the walls and brick work. Flat roofs are the worst, water can’t run off and simply sits on the roof.

get professionals asap!

Could it be the flat roof that has a leak somewhere? Water might be getting under the roof covering and soaking through the supporting structure.

We had an ongoing problem with a patch of wet/damp wall for years. Paint kept peeling off etc. I finally managed to persuade the builder who had constructed the flat roof about 7 years previously that it had never been right from the outset. He stripped the wooden decking off the roof and then the rubberised membrane. A small split was discovered in the membrane and the chipboard layer beneath the membrane was completely saturated! We had the whole thing stripped back and redone (this was in 2020) and, so far, no recurrence of the problem.

Please stand back and take some wider pictures. If it is coming through the ceiling it is probably roof or gutters. I can't see how your downpipes are arranged. From an outside window you can probably photograph the extension roof.

Is the water in the boxing-in round the RSJ holding the wall up where the extension was added?

If you have a wet patch on a plasterboard ceiling, pierce a hole in it with a skewer so the water can drip out into a bucket.

Well I sent pictures of the roof to my husband and he definitely seems to think the the pooling water is a problem and why is there no drainage.
I don't know if it is causing the issue but seems like something we need to look at.
The damp wall is towards the back left of the extension by the fridge. It's definitely not the fridge as we moved that away from the wall. I don't know if there's any pipes there apart from the gutters on the external wall. There's no bathroom directly above it only a bedroom behind the extension with radiator.
Either way looks like this is going to be a nightmare trying to find out.

I'm leaning towards roofing and gutters now, I have posted a pic of the extension roof but only so far as I can go outside the window.
I also don't want to post to many potentially identifying pics of the house.
But thank you everyone.
It is sort of coming from above and spreading downwards. Upstairs doesn't seem affected just the extension.
So dreading the cost of fixing this!

My guess is that the standing water on the flat roof is getting in.

when it’s dry up there ( if ) get a tin of the temporary roof sealer and seal where you think it might be coming in …. Then wait to see if any more comes through. I had this once with a lead valley, couldn’t see where the water was coming in, turned out to be a small hairline crack in the lead , sealed it , waited , problem solved, gave me time to get the lead replaced properly.

a huge amount of water get get though the smallest gaps.

it’s possible that it’s coming behind the lead flashing and running down the ceiling joists to where the leak is ?

We had water ingress with a pattern a bit like that. Rain was hitting the side of the exterior wall and coming in via the lintel. The drip tray (not sure what it's official name is called) to catch the water ad been put in up side down.

The standing water is normal after rain, but should go pretty quickly.
Stick your head out of the window above the leak and take a couple of pictures, maybe the flashing there has failed.

Our oldhouse there was a leak everytime it rained heavily in bay window downstairs. Always in the same spot. A friend came and fixed it several times in bay window upstairs, to no avail. Eventually I said , as water tracks could the leak be from the other side of the bay upstairs. Bingo. Water is a sod. Check your insurance for 'track and trace' ?? for water leakages, as often the origin of the leak isn't near to where the stain or drip is. Not sure if this situation will be covered by your insurance but worth checking.

Since you've just moved in is this something that should have been picked ip on the survey ?

So pretty sure we found out what it is, you can't see unless you go up on the extension roof, but there's an area in the corner where the roofing has worn away and the previous owners have obviously filled it in poorly. On the left hand side directly above where the leak is!

So instead of waiting 2 weeks for builders insurance to come out we are going to pay for a roofer to temporarily sort the issue, then in the long term we might have to redo the whole roof. Thank you everyone.

Ok one more question, this is where we think the leak is coming from as its literally right above where it is.

What do you think it will take to sort, any ideas? We are going to get a roofer to take a look but have temporarily filled it with waterproof sealant.

Thanks.

It looks like the downpipe needs to be removed and the lead flashing extended out to the right, then the downpipe refitted.
However that means you need a friendly neighbour.