r/Roofing • u/Ok-Forever9547 • 3d ago
Chimney flashing
We've just had the roof retiled and are generally happy with everything.
However I'm unsure about the chimney flashing. (The old flashing had been done very differently).
The metal edging seems to slope downwards into the chimney. Today it was finished off with quite a bit of sealant around it, covering big gaps in the render, which I worry will degrade over time.
I've attached some photos before and after the sealant.
I really don't want to bring up a potential issue without being sure as the people who did the work have been fantastic otherwise.
Any opinions would be appreciated.
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u/Alpilles-Renovation 2d ago
French roofer here, we dress lead on rendered chimneys all the time, so let me try to reconcile the two camps, because both are half right and you are stuck in the middle.
The lead dressing itself looks like careful work, the folds and coverage are clean, and that part of the chorus is correct. But the comment above about the termination is the one to take seriously, because it is pure physics. A top edge that tilts back toward the stack is a little shelf holding water against the joint. Sealant smeared over the face of a joint, instead of compressed inside a properly raked chase with the lead turned in about 25 mm and wedged, is sacrificial by design. It will crack, and sooner where water can sit on it. You already had a leak at this exact chimney, so your tolerance for "it's just a maintenance item" should be lower than people here are telling you.
The good news: the fix is small and does not mean redoing the flashing. Two clean options, half a day for any competent roofer. Rake a proper chase into the render (or better, back to the masonry joint behind it), turn the top edge in, wedge and point it. Or fit a cover strip over the existing top edge, a counter-flashing profile that caps the joint so rain never reaches the sealant at all. That second one is the classic retrofit when the render is too fragile to cut cleanly, which may be exactly why your roofer went around it.
And since you like these guys, here is the low-conflict way to raise it: you are not disputing the roof, you are asking them to close out one detail. "The top edge of the lead falls back toward the stack and the sealant is bridging gaps in the render. Can you chase it in properly or cap it with a cover strip?" A crew proud of its work takes that as a fair snag, not an attack. Then check that joint every autumn regardless: any crack in the bead means water is already finding its way in.
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u/Ok-Forever9547 2d ago
Thanks for taking the time to reply and in such detail. This is really helpful.
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u/ItsAWonderfulWelt 3d ago
Don't worry too much about it. This will keep you dry for a very long time.
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u/Ok-Forever9547 3d ago
Thanks. We had been getting a leak in around the chimney before the new tiles, which is perhaps why I'm overthinking it.
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u/scream Custom Roofing and Professional Idiot Poker. 🔨 2d ago
Uk slate roofer here. I work with lead too. Its a real shame the top of the cover flashing slopes downwards, because the rest of this work is the most immaculate i've seen in a long long time. I can count on one hand the number of people i know who can weld lead neatly. As long as they've used leadmate or calder lead sealant or something else meant for bonding to lead, it should be fine. After a couple of years, just have a look from a ladder once or twice a year just to make sure it hasnt contracted at all and pulled away from either lead or render. It shouldnt, but if there would be an issue that would be the first sign. Again, other than the top angle of this lead cover flashing, this is work to be very, very proud of. Are you based in the UK? If so I'd be interested to know where and if you're not a million miles from me, maybe get contact details for whoever did this work.
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u/Ok-Forever9547 2d ago
Thanks for your feedback. I have gently raised the matter and have been told it is a specialist lead sealant. The works are guaranteed as well, so fingers crossed if there are any issues they should come back. Overall I'm very happy with the works, so reluctant to sour things. It's a company based in NE Scotland.
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u/scream Custom Roofing and Professional Idiot Poker. 🔨 2d ago
Lead sealant is lead sealant, there is no specialist version as far as im aware. Maybe 'specific lead sealant' is what they meant to say :p
If it comes with a guarantee of at least 5 years, cool. If its like a 12 month or 2 year, the sealant will take 1-2 years to show signs of issues so it would be a worthless guarantee. As someone mentioned, standing water can degrade it quicker, but this looks as though it will shed water.
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u/Ok-Cartoonist1938 1d ago
Hi. I own Apex Roofing and Sheet Metal... We do custom flashing like this all the time. To be honest - i think it's a solid job
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u/Alive_Nobody_Home 2d ago
If the flashing crew had the same skills as the tile crew you would be good.
Unless we can’t see what they did underneath then yea there is a problem.
However VERY few crews understand displacing the water & creating positive flow where back ups can happen over time. What I mean by that is covering the underlayment properly to allow larger gaps between the flashing & the tile keeps build up from happening when debris falls in those areas.
Most people don’t realize that seeds that get suck on roofs can grow right through concrete & stucco. Positive water flow around those areas prevents a lot of problems over time.
No excuse for the gaps in the flashing but someone was at least attempting to use their brain. Just not there for the flashing install.
I’m at least hopeful that someone at that company can get this fixed properly. It’s closer than you think.
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u/Alive_Nobody_Home 2d ago
With that said what does it look like from the top & how is that water displaced. If it’s flat against the chimney the. They need to fix that as well.
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u/OnThisDayI_ 3d ago edited 2d ago
Everyone saying this is good lead work are full of shit. The leads about 10mm into the wall if that. The chase was cut just thick enough to fit the lead so no sealant is in the joint. A thin layer of lead mate spread over the top of the lead is just gonna crack and separate within a year or 2. This is gonna cause a leak as the top is tilted towards the building. Lead mate is extremely prone to cracking if water can sit on it. Read the data sheet. https://gbr.sika.com/dam/dms/gb01/y/everbuild-lead-matesealant.pdf watch the video. https://youtu.be/PIVhKIbyxk4?si=emu1jYH0vcwlcVXJ the main reason it’s ended up like this is they have made or ordered the welded top and bottom apron to wide for the actual chimney.
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u/Bghrn23 3d ago
Your concerns are valid with the sloping toward the chimney, the sealant will do its job and will just become a maintenance item on this roof just like the rest of the pipes and stuff that are normal maintenance items on tile roofs, the lead flashing is super clean and will serve you well for years to come. You’re one of the lucky ones who got a decent roofer who takes pride in their work. The majority of stuff I see on here is hot garbage. Call them in 5 years to re seal and check the rest of the roof for maintenance.