Leak on chimney lead back gutter

[johnny2007]

Good evening roofers.
First of all, hats off to you for being on roofs everyday.
I was up there today for an hour and it was unpleasant: cold, windy and every passer-by has to say something to you.
A few days ago it rained very hard and I spotted a wet patch exactly along the line of the chimney back gutter.
Then it stopped raining and it dried out.
Then it rained again and immediately I saw that patch again; it's in the 10 year old loft conversion btw.
So today I went up there and I couldn't see anything too bad.
The lead is intact, the tiles are fine and lined up.
The only thing that it was a bit off was the pointing along the lead.
So I scraped all of that off (it wasn't difficult, I just used a screwdriver) and replaced the mortar with Soudal lead mastic.
See pictures before ands after.
Now, considering that there are 2 layers of lead, one covering the other, could it be that the leak came from the broken pointing or it's something else.
Got to say, I will repoint the all chimney this summer because it looks a bit frail, but I don't know if that can lead to a leak rather than dampness.
Any comment is very welcome.
Thanks

 

[DAZB]

It is possible and as that seems to be the only obvious flaw then it is fair to target that area first and watch what happens at the next rainfall.

 

[datarebal]

Back gutter poorly detailed

 

[johnny2007]

Back gutter poorly detailed

Can you please point out what's wrong with it?
It was fine for 10 years and nobody touched it.

 

[datarebal]

The corners are poorly formed and short . There appears to be a slip of lead slid under one corner.
Lead expands and contracts something may have moved .
Of course , there may have been a bit of ingress which could have been picked up by the underlay for a while

I'd be surprised if another doesn't comment the same

 

[johnny2007]

The corners are poorly formed and short . There appears to be a slip of lead slid under one corner.
Lead expands and contracts something may have moved .
Of course , there may have been a bit of ingress which could have been picked up by the underlay for a while

I'd be surprised if another doesn't comment the same

Which one is short, the one I marked red or green?
There's no bits of lead slid anywhere, it might be the picture.
Anyhow, I lifted those edges a bit and put sealant there, I had a feeling about it.

 

[noseall]

Back gutter poorly detailed

We have ours made, for that very reason...

Ing4

• noseall
• 20 Mar 2021

Ing3

• noseall
• 20 Mar 2021

 

[^woody^]

The pointing does look porous, and there does not seem to be a drip on the capping slab.

 

[johnny2007]

The pointing does look porous, and there does not seem to be a drip on the capping slab.

Yes, the pointing needs redoing.
The drip on the back of the capping slab has broken off, but there's a deep groove there and when testing with a hose, water drips as intended, it doesn't run down the bricks.
BTW, is there anything on the market that can be used to repair a broken drip?

 

[johnny2007]

Update on this.
Yesterday it rained all day and no leak.
Maybe it was the broken lead pointing line that was letting water in.
Hopefully it will stay dry until better weather when I intend to repoint the chimney and somehow fix the broken edge on the crown.
I was thinking of making a small cast and use toupret murex for the repair, then seal the crown with concrete sealer.
Although, as said, the drip groove is quite deep and water doesn't run down the bricks.

 

[johnny2007]

More torrential rain today and still dry.
I must've been lucky with the easy fix.