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Leaking chimney - pointing? flashing sealant?

Joined
29 Dec 2014
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Location
Wiltshire
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United Kingdom
Hi

I know impossible without pics, but if I can explain whats what it'd be nice to hear alternatives to my ideas

1933 house, chimney with 2 pots/channels, one capped, one in use for log burner (new 25y one in 2013). Roof was "reroofed" in 2013, so new battens/membrain/leadwork and same tiles. High quality job. Lead work was done by a specialist leader in their team and it looked perfect and was seam welded. (pic is from 2013 when it was done). No prior concerns over the work that was done and for sure last 11 years been perfect.

(though I'm sure in the flesh there is more of an upstand on the lead on the south facing wall than appears in the pic, and I'd have expected the lead to have diagonal steps rather than vertical, but as I say they were an expert team and didn't rush (fair fixed price) and it has been fine)

The front of house is south facing, so the pic below is looking north.

Screenshot 2025-02-23 172804.png


Been up in loft today and (as always) no sign of ingress anywhere else, but on the chimney inside the loft there is water coming in at the loft side front side (south west corner). I've run an inspection camera inside the eaves to the chimney, and there is cracked mortar pointing that is soaked but no sign of water running down onto it, so I'm *thinking* it may be coming from inside the chimney or from behind the flashing and then wicking through?

I DIY'd the rear chimney a couple of years ago as the pot had cracked and aerial (unused) hanging off - and some of the mortar was like sand and just pulled out and a brick at the top was loose (as were the pots!!!)) and the flaunching (and pot) just lifted off :o So remedied all that and ground out and repointed all loose mortar but 2y ago the front chimney looked OK (alebit I didn't get to the far side, a bit challenging for DIY, or look too hard as no problems). But its likely the front chimney may be similar - though the rear got the brunt of the weather. Yes, hindsight says I should've moved the scaffolding forward, I did but it was a quick check, should've done more :(

I obviously need to hire scaffolding and get up and look when the weather is good, but I'm thinking

1 - pointing may be cracked/crumbled, so test and scrape out all and re-do
2 - the bricks at top, or pots or flaunching may be loose, so test and re-do as necessary
3 - the "sealant" or whatever they used above and to the side the flashing has perished and need checking/replacing.

(or crud/moss or something)

I don't think it will be the leadwork per se. And don't its a tile problem (no sign of water on the membrane)

Seen other threads mention a "tray" may I ask what this may be or when they became standard? If its something internal to the chimney how did the logburner installer "easily" get a big flue down the chimney lol! If its a ridge inside the chimney would that (could that) be at eaves height? if so could that suggest water is getting in from the top or through high pointing, running down the chimney, and then pooling and exiting into the loft through the internally cracked (and 100% impossible to get to!) mortar?

But any other suggestions?


Pics of OTHER chimney 2y ago

Screenshot 2025-02-23 173359.png
Screenshot 2025-02-23 173338.png
Screenshot 2025-02-23 173315.png
 
Last edited:
Internally, overnight, you can see the water in both rear corners. I can't believe both corners have failed as guessing water is getting in somewhere and tracking. Can't see the rear without scaffolding, so thats arriving end of week

The loft floor is concrete in that area (surprising to me!) so assume a little amount of water has been able to get in and sit on that and evaporate off and its only rarely gone into the bedroom below.

Without looking its tough to say, but my money is water in via the top, or some pointing/lead sealant to the rear....

The membrane and top of that wood going parallel to the chimney is dry so don't think its water from the rear tiles or anything "before" the lead.


Screenshot 2025-02-24 102420.png
Screenshot 2025-02-24 102437.png
 
More pics from a look on the roof today.
Sadly my dream of seeing something obvious was crushed.

There are some vertical gaps at edge of the lead but thats how its done I think, and the membrane does go over the saddle so that looks OK. Rear gully was clear and pointing looks good. Not looked at pots/flaunching yet my arm aches too much to lift the last platform.

pointing looks Ok

No obvious failure that would affect both sides (obviously water can track)

Ideas welcome!

All pics from today here https://photos.app.goo.gl/mJdje8TRCfRvVe128

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AP1GczPYjl_6SAu9ejsFPYC5pA8yxqXRxD07ZQQVkfkSdNRzGtQc4HV8F_bMsJuQ8wrcGx16jYHLGkPjOVYnHOxH0LPulhvra2igI8ebFK-iJngwhZMUPxSYwHAJqNBw-_TgDPdNzu37LCZBZBw5T7_O9u5S6Q=w922-h1230-s-no-gm
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I'm not a roofer so take what I say with a pinch of salt, but if you are struggling to find out where the leak or leaks are coming from, have you thought about putting some different coloured/tracer dyes in some different tubs of water and pouring them separately over the areas you suspect might be at fault to help locate the problem?

Like I said, I'm not a roofer but I'm just thinking off the top of my head.
 
Video added to the gallery above

Found quite a few ways in. Think its beyond me to do safely at height. :(
 

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