Stone chimney and lead flashing

Markcheese

Currently having the roof done on my 150 yearold cottage ... We knew we had an occasional small leak near the chimney. Builder has started stripping the plaster back on the old (sound) stone chimney and reckons it was reflashed prob during 80s.
Upshot is he reckons it'll leak again and suggests removing the stone chimney and replacing it with a concrete one which he can recess the lead into.
It'll be a pig of a job and if I can avoid it and save the sound stone I'd be thrilled...
So how do you successfully flash an existing stone chimney ....builder wants to start on chimney soon as the slating is waiting on the chimney .... Ta

Eoghan Barra

I would be v. surprised if what your builder is saying were true.

I had a house with a stone chimney and flashed it by making a cut about 20mm deep all around and inserting the top edge of the lead into that. Never had any problems with water penetration at all. This could also be done by raking out strategic horizontal joints for the same purpose.

wayoutwest

Why can't the roofer just replace the leadwork -if, as you say, the stonework is sound. It may be a case of angle-grinding a recess for the lead to fit into [if the present flashings are just stuck against chimney] - but it could be done and would be effective SO LONG as any cracks that appear in the new render are repaired,so not to let water into the chimney coursework.
Old houses are'nt built on concrete foundations,they do 'move' a bit and the cement- rended faces of the chimney, are particularly prone to cracking.
With this in mind,your roofers' suggestion of chopping/rebuilding,is the only way he can fully guarantee that there are no leaks in the future.
How much more is the rebuild going to cost, over 'making good' the old one?

Markcheese

Thanks lads.Currently the lead is just against stone, it's just a rubble stone wall, i'd reckon if he put an angle grinder on it he'd make ****e of it... He's taking the view that what was there before leaked, if he repeats what was done before, it'll leak again... Get the feeling he'd rather not rip it down completely ( it's a shared chimney and the neighbours roof ain't great either, he might end up in neighbours living room )
But there must have been a way of waterproofing it in the past , as the old timbers (at least 40 to50 years old) while water damaged had not rotted out ....

wayoutwest

Its' a nasty, dusty job allright.....I've done a few.
If, what was there, was leaking - and the leadwork did'nt have holes in - then, the render and/or the capping above must breached [it could be a hairline crack] - sending water down the coursework and behind the lead...[that has'nt been 'chased']............On close up inspection, just how 'sound' is your [and your neighbours'] chimney in this respect?

Markcheese

wayoutwest wrote: »

Its' a nasty, dusty job allright.....I've done a few.
If, what was there, was leaking - and the leadwork did'nt have holes in - then, the render and/or the capping above must breached [it could be a hairline crack] - sending water down the coursework and behind the lead...[that has'nt been 'chased']............On close up inspection, just how 'sound' is your [and your neighbours'] chimney in this respect?

The render and the capping are a total mess.. And were being stripped replaced anyway...the lead itself was fine... It was just laid against the stone work (beneath layers of plaster...)
The builder is just concerned that I'll ring him in 2 years time giving out about a leaky chimney ... So he's laying it all out... Ultimately it's my call...

Markcheese

Update... Stonemason coming out to have a look at chimney to tell me how best to flash it....I'll pass on what he says ...

wayoutwest

1]After the face has been dubbed out [flattened] by applying mortar to missing pointing and any hollows - decide on new flashing line.

2] Angle grind 1" slot that is wide enough to take the thickness of lead + securing 'wedges + sealant.

3] Insert the lead and then cut 3/4" squares,bend them in half and gently tap them into the slot to secure the flashing.

4} Pump in quality sealant [NOT silicone].

5] Two coat render[containg waterproofer] that includes a drip detail at the bottom, where, it can kick the water away from flashing.

......not a problem for someone who's used to working on old buildings and has done it before.:)


P,S - Markcheese - do you mind me asking how much you've been quoted for completely new chimney?

Markcheese

Upshot is .. Stonemason didn't reckon there was much use recessing the lead... Likely to destabilise chimney...and if there was a lot of water/ moisture flowing down the stone face then (with porous stone and lime mortar ) I'm in trouble anyway... So strip the chimney fully of plaster, flash replaster, new cap.. Done... Builder happy as he can crack on today...
Builder had estimated at least 1000 euro and 3 to 4 days to replace the chimney.... Hope it all works out alright...

wayoutwest

If the stonework is is a complete, crumbling old mess -then go for it.....it will be a better job - that wll endure the elements and require less maintainence [filling cracks],over the years
P.S - Before the builder caps the newly built stack.....have you thought about chimney flues/liners for stoves etc that might want to be installed ?[maybe in the future].......would be shame to mess up your capping down the line [insulating around metal flue and securing any flue clamps].


Good luck... u just need a few dry days ! :cool:

Markcheese

wayoutwest wrote: »

If the stonework is is a complete, crumbling old mess -then go for it.....it will be a better job - that wll endure the elements and require less maintainence [filling cracks],over the years
P.S - Before the builder caps the newly built stack.....have you thought about chimney flues/liners for stoves etc that might want to be installed ?[maybe in the future].......would be shame to mess up your capping down the line [insulating around metal flue and securing any flue clamps].


Good luck... u just need a few dry days ! :cool:

Aaagghh , forgot about the liner... There's no stove .... Yet, but it was part of the plan, there was a flue liner in a different chimney (now gone ) that was going to get swapped across, but it didn't survive .... And I forgot afterwards... .... Have to check the depleted piggy bank ...
Builder up at chimney now... Hope it stays dry...

Munsterly

Has anyone an opinion on Kemper Systems? Renovating a 150 year old house also and builder trying to convince me that this sealant stuff is more effective than lead flashing.? The chimneys on both sides need to be reflashed and also the valley on the roof between neighbouring houses on both sides. Building spec specified lead flashing but builder decided without consultation to use Kemper instead. Have put job on hold until I can find out more about the stuff and how effective it is. Also is it more or less expensive than lead?

hexosan

Munsterly wrote: »

Has anyone an opinion on Kemper Systems? Renovating a 150 year old house also and builder trying to convince me that this sealant stuff is more effective than lead flashing.? The chimneys on both sides need to be reflashed and also the valley on the roof between neighbouring houses on both sides. Building spec specified lead flashing but builder decided without consultation to use Kemper instead. Have put job on hold until I can find out more about the stuff and how effective it is. Also is it more or less expensive than lead?

If the builder chose it without consulting you, you can be sure of two thingsits
A). Cheaper than Lead
. Easier for him than using lead

Munsterly

Thanks. That's what I figured. Do you anything about that product?