Chimney crown to be lead flashed?

[FiRiv]

Hi all,

At our wits end with a chimney that has been leaking for over a year now. Done roofing work, followed by a lime mortar mix on the chimney crown top. It’s a four stacked chimney and the water is still coming internally into the building (not inside the chimney). Roofer is now adamant that we lead flash the whole top of the chimney which doesn’t make sense to me at all but he is insisting that lime mortar soaks up water and it must be coming through this new mortar topped chimney. Only one side of the chimney is not rendered and so I feel it must be partly this although it’s a very large area crossing two/ three internal room ceilings, so there may be a few areas. Could anyone comment on the effectiveness of leading the crown of a chimney and whether a lime mix mortar should be water tight? Thank you

 

[Itchinfilth]

Is the roofer suggesting going over the flaunching with lead?

 

[FiRiv]

Yes he’s suggesting putting the lead on top of it to make it watertight

 

[alexander]

how is he going to vent the different flues sealing the chimney completely is not the best solution, are the chimneys capped,

 

[FiRiv]

Flues wouldn’t be affected as he’s suggesting leading the base of chimney on top of the white lime mix mortar (it’s a big chimney!) and yes chimneys are capped as pictured. Surely this lime mortar mix is water tight and any water entering is sliding down the sides here?

Last image is lower down on the chimney that I believe is where part of the issue is as it’s not flashed properly and there’s exposed brickwork. So grateful for any thoughts

 

[Cubist]

Lime mortar is not impermeable and will absorb water just like the rest of the chimneys masonry. Your roofers recommendation is to divert water away from the foot of the chimney where it intersects the roof structure. Without this you would have water literally running down the internal walls.

 

[FiRiv]

Ok thank you, I suppose I’m just a bit sceptical as it’s been primed painted and sealed so thought this would stop rain coming in. We also had a leak detector come and hold the hosepipe on the top of the chimney/ lime mortar mix and couldn’t see any water coming in from there but maybe we need to test it again. I just want to be sure that expensive lead capping is going to sort the problem out

 

[Cubist]

Frankly I'm surprised the leadwork wasn't done before the render, sealant and paint was applied. Did the roofer offer any explanation why he did the work this way?

 

[FiRiv]

He said it was a process of elimination and by doing the render first we would hope that sorted the problem out but that because we had to do it anyway (for the lead to go on top) it was worth trying that first and then if it didn’t work to do the lead on too. But why one would recommend that course of action when they knew that lime mortar was (or could be so porous) I have no idea!

 

[Robola]

Surely repointing and repairing the clearly damaged bit lower down should be a priority . There are open joints and bits of flashing flapping about, even the gutter is full of rubbish.

 

[FiRiv]

Yes I agree - waiting to confirm that this was work that the existing roofer did and if so he should rectify as it’s only lasted a year…although he’s told us if we render that side of the chimney we should do the lead capping first, so either way he’s recommending that we do the lead capping

 

[Cubist]

Assuming I'm understanding the sequence of events properly then I cannot say that I'm impressed by the original roofers advice or work and I'm a little dubious about your new guy. Any competent and honest roofer having been told that water had been observed on the chimney structure/walls indoors would have concluded that the key priorities for examination would be the interfaces between the roof and the chimney, the condition of the leadwork/flashing and the bond of the latter to the chimney masonry. The condition of the flaunching and any render above it would only be relevant if water had been detected in the flues and around any open hearths in the house. I suspect too that the 'leak detector' you employed was little better than a charlatan and I would not rely on any advice from anyone claiming that capability or aptitude for hire.

Given the state of the leadwork shown in your latest photo, which I am assuming was taken recently and of the base of the chimney beneath the scaffolding planks previously shown, then the source of water entering your home is painfully obvious. That leadwork has been dislodged for some time and rainwater from the roof and the chimney sides has been running toward and into the lead gulley. Some of that rainwater will have got behind the leadwork to fthen flow down the walls internally. You may also find that the lead in those gulleys has worn thin - yes, water can erode lead over sufficient time - and holes may have formed or been punched into the lead by falling rubbish from the work undertaken above.

It may prove expensive but all that rubbish needs to be cleaned out of the gulleys, the extant lead carefully examined to ensure there are no holes or tears anywhere else that rainwater may reach, and that the lead is properly jointed into the chimneys masonry where needed.