Chimney breast leaking

Roky2018

Hi,

I’m running out of ideas what’s causing damp/wet patches on second floor chimney breast wall. I installed new chimney cowl with new liner, I tanked external chimney, around chimney lead looks ok, in the attic all around chimney bone dry…only in the winter when bad rain hits season.

greasepalm

If i see a crack on those photos what is up on the roof i wonder , when you said chimney was that the pots or all of the brickwork going down. Old brickwork can be like a sponge drawing it in.

All brickwork needs is a crack to get drawn in as whats below shows.

Roky2018

External chimney bricks is in good condition, as I said its fully tanked around , crown been tanked 2, there is no single crack on the chimney or top…after I tanked I replaster chimney wall breast, I thought problem solved, but this winter problem a-pear again, not that much but still as you see on first picture.

Roky2018

May same one had same issue?

Field east

https://www.boards.ie/discussion/comment/121756141#Comment_121756141

A few relevant photos of the chimney from the outside might be more informative

Roky2018

Pictures

niallb

What goes up the chimney?

Is it an open fire, stove, or exhaust from a boiler?

If it's a boiler have you had it upgraded in recent years? Modern condensing boilers have much cooler exhaust which could condense inside the chimney and seep into any crack in the lining.

Roky2018

I got insert stove with liner installed all way up…all summer perfect was, before heavy rains started.

Doolittle51

Could the issue be originating further up the roof? Water coming in at the ridge for example could travel down the felt and cause damp where it meets the chimney.

Roky2018

I lifted last summer lead and tiles, I seen same stains around, but didn’t see any noticeable dampness….just my thought’s, if lead fails, I would be seeing marks or stains in the attic, but attic bone dray around the chimney …

10-10-20

How is that lead flashing bonded to the render? Was it cut into the render and then fitted into the slot, or is that just lapped up-to the render and then bonded directly using the lead flashing filler - I can't tell from the photos.

Roky2018

I think it was lapped up and rendered on the top…

Roky2018

Same pic.

10-10-20

https://www.boards.ie/discussion/comment/121756910#Comment_121756910

Then in my opinion that's the most likely cause of any leak. The lead should be cut into the render/block and then sealed.

Example in the initial images here:

https://www.buildingconservation.com/articles/weatheringwalls/weatheringwalls.html

Roky2018

What should I do? Take them out all together and if there is no cut in, than do flashing with cut in all around? How deep to cut? Do I need hide flashing lead with the render couple mm?

Roky2018

Thank you for advice…but just wondering how water could go behind??? It’s all way down tanken fully even lower bellow flashing.

Roky2018

Thinking loud, if that be the case as you saying lead issue with chimney , means I would be seeing damp patches or satins in attic on chimney bricks?? But there nothing

10-10-20

You added two photos which I hadn't seen. From them I think that the lead tray might be installed correctly as it's lapped under the upper section of lead which I'd guess is bedded into the blockwork. Only by opening the render at a point would you know for sure. 🤔

https://www.boards.ie/discussion/comment/121757011#Comment_121757011

If the lead is only bonded to the blockwork then It's actually the exact same as what's being discussed in this topic:

https://www.boards.ie/discussion/comment/121623034#Comment_121623034

The lead flashing only collects what hits and runs-off the exterior of the chimney but wind driven rain penetrates the paint and render on the chimney and the water tracks down the path to the base of the chimney, causing the leak.

listermint

From what I can see I think the lead needs to come out. Clean behind and redress. Probably one for the drier months though I'd want some level of warmth on the brickwork.

10-10-20

That's the overlapping detail there that looks fine except what we can't see behind the render. If that lead lead is solid then I'd be thinking of running a hose over the tiles and just up to the base of the lead (on a dry day) and then see if it's leak at the lead and tile level. Then try wet the chimney after that if it still remains dry.

listermint

https://www.boards.ie/discussion/comment/121757254#Comment_121757254

Seeing copious amounts of used silicon on that. Warning bells !

10-10-20

Actually just spotted something... might be small.

Does the upper lip of the lead at the left of this photo go right under that second row of tiles or is it border-line? I'm kinda still thinking that it's the render as I don't see water staining or rot on the battens...

10-10-20

https://www.boards.ie/discussion/comment/121757266#Comment_121757266

True, but could just be a repeated attempt to fix something that isn't the issue. But I'd still suggest that only removing some of the render will answer some of the questions here.

tanked external chimney

Just going backwards OP... Do you mean tanked under the fresh paint using a bathroom tanking product, or what?

listermint

https://www.boards.ie/discussion/comment/121757285#Comment_121757285

True. Good shout on the length of lead. Looks to be 20 mm on near side tapering over to 10mm on the further side. Very limited coverage under second row of tile.

10-10-20

https://www.boards.ie/discussion/comment/121757290#Comment_121757290

A second thin sheet of lead or even DPC plastic wouldn't go amiss there.

niallb

https://www.boards.ie/discussion/comment/121756613#Comment_121756613

Plenty hot enough so.

Were you having damp problems before the stove was installed? That looks like a lot of water in the wall.

Have you seen the seal of the flue liner to the top of the chimney and cowl? Water coming in there could explain why the attic is dry. I'm curious as my dad had a similar looking problem on his house and had the chimney rebuilt, part of the roof replaced and redecorated only to find it as bad as ever the following winter.

In his case he realised that he'd removed some broken chimney pot pieces from the fireplace much earlier and that some must have hit the angle on the chimney on the way down. He's an engineer and one back of an envelope later realised how fast it would have been going at that point. The crack was about halfway up and resealing the chimney and fitting a flue solved it permanently for him.

10-10-20

https://www.boards.ie/discussion/comment/121758000#Comment_121758000

Exactly, capping stone or such isn't mentioned.

greasepalm

Photo in post 20 i can see a gap to the right of red marker going down the roof . Also agree on the iffy silicone put on

spaceHopper

A good roofer will have this sorted for you, and probably won't cost as much as you think. Had two leaks in my roof fixed for 300 euros in about 45 minutes. Granted it was cracked tiles and easily fixed. Your's will take more.

Squatman

https://www.boards.ie/discussion/comment/121758094#Comment_121758094

bingo. capping stone is the culprit

Roky2018

There is 2 coats weather proof slurry applied and painted on the top external chimney …there is no chance even drop any water from lead tray couldn’t penetrate in to wall…

Roky2018

https://www.boards.ie/discussion/comment/121758000#Comment_121758000

I installed liner with attached cowl on the top…there no water coming from top even I applied bitumen sealant on top chimney crown. That what though in first place that water coming from..

Roky2018

https://www.boards.ie/discussion/comment/121758224#Comment_121758224

Caping stone or chimney crown was painted with bitumen sealant fully.

Roky2018

https://www.boards.ie/discussion/comment/121758203#Comment_121758203

I had roofer on site, he didn’t have clue, what he was saying everything was done all ready.

Roky2018

https://www.boards.ie/discussion/comment/121757254#Comment_121757254

Thats what I was thinking 2 👍run hose in the summer, because running out of ideas.

cnocbui

I had a chimney leak. Expert trades people quoted to tear down the chimney and rebuild it for about €2500 - might have been more, was a while ago.

Did the obvious stuff like checked the cap and the seal between that and the flue pipe. I did notice some barely visible hairline cracks in the render, and I do mean barely vissible.

I looked into flexible renders and got some quite expensive German silicone based stuff intended for rendering external insulation Relius. Re-rendered the chimney with this stuff, and sure enough, no more massive leak and problem solved.

If you are near Tipp, you are welcome to what's left. Well past use-by and I'd have to go open them and check they are still usable and the quantities. One is the undercoat and the other the render. The undercoat is/was near full. Honestly, I think the only difference between them is the amount and grade of sand in them and that the undercoat would probably have been sufficient as it would cover and wick into the fine cracks.

Not bad fixing a €2,500 problem for €120

Roky2018

https://www.boards.ie/discussion/comment/121758764#Comment_121758764

Thank you for tip…I did with this…I thought 100% problem solved , but wasn’t the option…I think it’s better than it was before, but still wet damp, after storm rain