4 Roofers Couldn’t Solve This Damp Chimney. Can You? 

Sorry but to me that looks to be extremely poor leadwork. Too many people don't even know about Soakers or the need for substantial overlaps to keep wind driven rain pushing water up over Soakers if they are fitted, and around Corners, the only way imho to ensure that it is a good job, is to take it apart and start again from scratch. If ot is done properly, Roofers Tippex (Low Mod Neutral Cure Silicone) or Mastic are not needed. tbh, we need to start up proper Apprenticeships again, withbsome decent Roofing Courses at Colleges again. Our Apprentice was on the last Roofing and Slating College Course in Wales, believe it or not, and did an Exhibition Roof Competition at the NEC. He was the inly one who finished off the last course of Slates at the Ridge Properly and securely. The Construction industry is in a bloody bad state all around sadly, and not just in Britain and Europe, it's a Global Problem. Best Wishes. Bob. 😔

So refreshing to hear a builder advocating lime mortar these days! Thank you for the video, Roger

Roger - literally watching as I’ve a 1930s property bit of a leak down the inside of ours and thought “Stormdry” brilliant stuff would recommend to anyone but didn’t think it would be suffice on a Chimney! Your a legend fella 👍

Another great video Roger, you could (and should) make a full series on common chimney problems. I’ve lived in properties where chimneys have been taken out badly creating structural issues, others that have leaked and been damped like this one. And I’ve found that some roofers don’t want to get involved and some builders just pass it off to roofers.

Hi Roger, Looks to me like the soakers are Not over lapping so instead of discharging the water downwards its going straight down into roof space. That indicates whoever did it doesn't understand the principle of flashings and there could be other mistakes with it out of immediate view. Met a few roofers who didn't understand about soakers.

Really useful video. I have been working my way through the same issue and had decided to use Stormdry next summer. Stupidly I have closed off the chimney to stop the draught in my lounge. So will also open up the chimney (hadn't thought of that before seeing this video).

You mentioned a drone for getting photos. I used some plastic pipe I had laying around taped together with a camera strapped on the end. The flexiness meant it kind of hung over the ridge and pointed directly down at the gutter. A bit of trial and error but worked well.

I did up a house built in 1850’s and had this exact problem. Had a roofer up two times but was still leaking. After some thinking I came to the conclusion that the whole chimney was like a giant sponge. So spent £1500 to get the chimney replaced. Problem solved.

It's definitely coursed stone, looks like West Yorkshire (where I am) or possibly East Lancs. That strap pointing was done all over in the 60s to 80s. The structural mortar is of course lime mortar.

There's an option I used on two chimneys at my terraced house: render then with a drip strip at the bottom and finish with masonry paint to match the colour of the house walls. I also replaced the haunching around the chimney pot with a harder mortar with a steeper slope to shed rainwater and fitted a metal rain cap with mesh below. I love my woodburner but others can use the chimney to vent a gas boiler (or mount a TV aerial). Chimneys have many uses!

I had a similar issue on my chimney, different story, concrete block. The render had been frost damaged over the years a d water was getting in, wicking down and coming out in a huge wet patch in the wall, the concrete cap had gone porus as well I think, I re plastered it and built up what was missing from the cap, no problems since, I think part of the problem was the fireplace for that chimney had been blocked off for years and wasn't vented. I was redoing the floor in that room so I just broke into the old fireplace from under the floor, blocked it off in the room, and now we've good ventilation up through the chimney from under the floor, I think that has a good part in keeping it dry too.

A few years ago, I had a similar problem with a damp chimney in the attic of our c1912 home. The builder I got in to examine it could find no problem with the structure, render, flashings, etc. The only thing he could suggest was a chimney pot cap to stop rain dropping down the chimney but he couldn't find a cap that would securely fit the oddly shaped pot. I made a cap from 6mm stainless steel plate, which I secured with homemade hooked clamps down the chimney. I also incorporated a 25mm galvanised wire grille at the top, under the SS plate to stop birds nesting in the chimney. The result was a completely dry chimney (& one impressed builder). 😊

I had a similar issue with the chimney being wet in the loft. The roof was 90 years old, so we replaced it and also had the chimney re-pointed. The issue continued, I applied stormdry to it and also fitted some chimney caps/cowls/tops. This was done in the spring and 2 years later I've not had the problem again and the chimney inside the loft has stayed dry.

The biggest issue in general is most chimneys don’t get used anymore. I had a job had looked couple times tried multiple things could not get it resolved then 1 time I went back up the the tiniest little pin prick on a welded corner sealed that sure enough resolved it water gets in anywhere

The stone/brick looks very porous, so pointing with a sand/cement mortar is probably not a good idea. Looking at the stain on the ceiling, I would think the problem is probably to do with the rear gutter. A couple of images of the back gutter may have made things clearer. I had a job where the gutter was holding water as it was blocked with organic matter, and when the wind blew the water went over the lead flashing and into the building.

I had exactly the same problem with our chimney, so much so I needed to catch dripping water inside the loft with buckets. I found a crack on the concrete plinth on the very top of the chimney so made a metal cover for that. Coated the whole chimney with Thomson’s water seal…..never leaked since. Interesting video, thank you for sharing.

Hi Roger. Agreed about the pointing. Regarding the waterproofing (stormdry or other), on chimneys, its must important that the haunching and pot are absolutely weatherproof to prevent excessive moisture soaking down the brickwork and overwhelming the breathing capabilities of the paint on barrier as this can exacerbate the internal damp problem.

Great advice, I’ve got a chimney with exact the same problem. I’ve checked the flashing and all possible issues for Water to get in. I’ve even added an extra event in the chimney to create more airflow. Mel has worked. The chimney is at the corner of the house so therefore there is no possibility for water to evaporate before going into the house inside the roof void. It looks like I’ll need to use storm dry to stop water getting into the brickwork in the first place. I have damp problem with two out of three chimneys all in sum on positions. The puzzler but I’m feeling that storm dry is the only option available, which I’ll do this summer. Thanks for the insight. Aidan

Hi Roger, I clicked on this one because I had too many good years trying to solve this sort of problem I did fail a few times and did manage to get to the bottom of most of them, the first thing I notice is that all that new plaster inside was holding all the water used in the mix, about three times as much water as dust!, all that water was just sitting there and as always takes along time to evaporate and even then if it cannot escape will condense on any cold surface. The next thing I was looking for was where was the damp inside?, if it is on the underside of the ceiling and how much is on the wall, the damp that I have seen on walls has never come through the roof, I am not saying that this cannot happen, just that I have never seen it. There was one chimney where I opened up the roof and found no visible issues yet there was some damp on the ceiling. Here you have roughly equal amounts of damp on the ceiling and the top of the wall!. You do not say if the new ceiling was fitted with a vapour barrier and insulation but even if it was it would have been very difficult to seal it at the chimney. The result of all that isn that I would have to open up all the roof from the front all the way up the side and across the back gutter seeking any water tracks, even then absence of evidence is not evidence of absence so re-instatement would involve a new back gutter properly fitted soakers and step flashing and front apron. There would be no guarantee that this would solve the problem!, the two other issues remain unresolved. the second of which is that the chimney itself if unused and capped can trap wet air which will be absorbed by the old soot, that has property known as hydrophilia!, it will soak up moisture if any is available, this moisture will then cool the brickwork when it evaporates the heat then comes through from the inside, the temperature inside can then drop to below the dewpoint of the air in the attic!. There were many occasions in the past when the eyes of the builder that I was trying to explain all this to simply glazed over!, in fact even now I do not actually know for certain that this ever actually happens, just that it is consistent with the laws of physics and chemistry!. I write this and post it to you in the fond hope that you do have the wit to understand it!. Cheers, Richard.

Use some stormdry or other brand on the chimney stack walls. Make sure the top of the stack is waterproofed with some slate on a slope or some domed profile. Then fit a Rain Cowl with Mesh or Aspirotor spinning Cowl. The spinning cowl is better because it helps the natural updraft of the chimney drying from inside to out. Point to note. Check the chimney for an opening or air vent down stairs.

I like the chimneys in Brittany, France, they tile them, seems to keep out the similar weather we have in the U.K.

Great show old man may God richly bless you thanks 😊

I could really do with your expertise, I have a problem with my chimney, I have had several people try to fix it, but every winter, sure enough we get some damp on the ceiling, flaking paint on the ceiling, salts coming out of the plasterboard and wall.... definitely want it sorted out, Croydon based here. The chimney is part of an extension that was built in 1996 and has apparently never been right!

🧐🧐great video mate i had similar job two years ago ..after replacing all lead work and felt batten etc correctly it was still coming back on bad heavy rain showers. on second attempt i did all repointing and could see The problem ..on removing the old cement it was getting behind and most bricks were saturated finally had solved the problem

I got fooled by a damp chimney breast. I went up & repaired the chimney rendering, checked all the flashings, ventilation cap etc. And what it turned out to be was hydroscopic salts from 90 years of fires had saturated the fabric of the chimney. So in damp weather, it attracted moisture just as leaving a bowl of table salt out does. I largely resolved it simply by painting the chimney breast with Stainblock & ensuring good ventilation through the unused chimney to keep it as dry as possible.

Roger, before even watching all your video, I was 99% certain it was driving rain getting through, I know because I’m a builder and have seen this a few times and even on my own bungalow. I live at a 1000ft in rural Wales, we moved 3 years ago and was getting water on our lounge ceiling, stack was soaking in the loft, I redone the lead, repointed, re flaunched it, still getting water, gave it two coats of Thompson’s water seal (not as good as storm dry I know) and it’s been fine since, I do it every summer now. Since then I’ve done it on other properties with the same results, you cannot underestimate how much driving rain will penetrate brickwork, they even call for minimum 120mm cavities here because of it.

I have only just remembered that I came across a similar problem to this many years ago in a loft room. It turned out to be condensation running down the felt (due to lack of roof void ventilation) and accumulating at the back of the chimney. Condensation could also take place near the top of the chimney breast itself as this will be relatively cold in the winter. Therefore, if the problem is absent in August its probably at least part condensation. If the chimney is used you would also get condensation on the inside as the warm rising air meets the cold building fabric close to the exterior. The other consideration is hygroscopic damps - the products of combustion produce many contaminants, some of which are hygroscopic and these salts may leach into the brickwork where they will absorb damp from the room - which may be humid. I noticed when last in France that they sometimes clad external chimneys with zinc to provide a rain screen as it is virtually impossible to otherwise prevent damp to a chimney breast which is only inches below a saturated stack.

Iv got the same problem and have been thinking of using stormdry on my chimneys after good results on a damp wall

As you have already hinted at it would appear the damp is trapped within the internal finishes - easy to say but it is advisable to open up internally , inspect and allow to dry out.

good video roger !! looks like its leaking at the back of chimney as the water marks on the ceiling is a telltail sign and can definately leak by the silicon holes by the flashings !

The rear of my house faces the weather - wind driven rain - and I gave it a coat of storm dry and I swear it even made the rear rooms warmer as well as waterproofing the wall, all for a couple of tubs of it!

Hi Roger . One of the potential problems for owners of older properties like me where sand lime mortar jointing dried out excessively due to last years drought . Unfortunately this led to wicking effect . So with the joints getting soaked by rainwater the internal walls can not dry out fast enough during the winter months . We therefore have to wait for the summer months to dry out the rooms .

Great video Roger, I'm with you all the way on the ribbon pointing. Not only can it lead to water ingress, it leaves the masonry vulnerable to frost damage. Another issue to bear in mind with chimneys is that leaks can wash hygroscopic salts (from soot) into the plaster. The salts then absorb moisture from the air keeping the plaster permanently damp even if the original leak is fixed.

Very pleased to see you now recognise cement mortar traps in damp whereas lime will help damp escape.....

1min 30 seconds in ….,thermal image the chimney breast & take photos Then garden hose out of the loft window & saturate the c/Breast ….thermal again Depending on outside temperature & fabric temp ….you should see something V difficult (but we have done it) connect G/hose to hot water from combi & spray area with hot water You then have the cooler brick work + hot water / now you have a larger temp differential….easy to find weak spot or spots

Iv had a roof issue at one of my BTLs for 7 years. Countless roofers couldn’t fix it. In the end I removed the chimney. Think theres still water getting into walls a bit but not as bad. Some projects make no sence.

I'd absolutely agree with the Stormdry treatment. Also what about the haunching and pots? Is the haunching cracked and crumbly? Are the pots still used and if not have they been capped against rain ingress (with ventilation of course!)

chimney being damp normally would show on the plaster on chimney breast in bedroom below ... looks like its coming either through a cracked or missing slate above chimney or more likely poor / damaged flashings around chimney. Far too strong a mix used on the stone work ..would of been better to use a lime mortar. There's premixed lime mortars available with lots of colours available now that helps make it a fairly simple process. Just read what Richard Harvey wrote and agree 100%. well done Richard for a well written explanation 👏

Interesting, i dealt with a stack with saturated bricks, even in the middle of summer with flashing that was fine etc. stack had been used to burn coal only all its life, my conclusion was that soot attracted moisture and kept the bricks wet all that time. In the end the stack was removed and the lower brick was coved with a independent stud wall with plaster board.

At 2:18 to 2:40, I can see that the chimney is leaning to the left; while pretty much square to the roof it isn't vertical. I don't know if that's a cause of the dampness, an effect, or just a red herring, but it doesn't seem right.

The thing with chimneys is that they are meant to be used. They are designed to have a good fire blazing away, and the hot fumes would dry out the brickwork. If this is not the case, then the chimney should be capped preferably with a lead sheet on a timber former. I agree with sealing the brickwork also. Both methods used together, will prevent water ingress past the lead flashing, as you covered with the dpc comment. The front lead apron would benefit from a bigger upstand, in line with the stepped flashing to the sides. Also, to me it looks like the plaster has been applied to the chimney directly, whereas it would have been better if it were battened out and plasterboarded.

The lead flashing on the side don't overlap each other for my liking . As said a water seal would help if nothing else is done , simple DIY job too

I often find a chimney rebuild with a lead tray. these old stacks were often built without them and were ok while as the damp had a metre or so to dry out in the attic.. the problem cmae when the attic was converted into a room and not allowing the damp from the outside to dry out.

I used Integral Waterproofer on a 1 to 20 mix in water with my sand, cement and lime. Also a bit of SBR and Rendamix for this external render

In the future you need to give out the area of where these houses are because not only might there be someone there who could fix it, but also local knowledge (of weather and materials) is very useful. It would also be good to know where the most winds are coming from in relation to the leaks. It looks to me like a North Eastern Lancashire house, possibly Colne or Burnley, somewhere round there. WDR and porous stone is a big problem in that area and the fact the house next door has been painted says something. I would agree with Stormdry, but need to warn you of something. If it's done with that and then needs repointing, the pointing won't stick! That is if it's managed to soak into the joints, maybe all that horrible strap pointing will stop it. The other thing to note is that some of the houses out that way (Pennines) get so much WDR that it even gets through Siloxane, wets the wall and still runs in.

I have a very similar problem. It seems like the brick is soaked and went black with damp. Flashing all looks sound. Had a guy come and look at it and sand blasted the brickwork and repoint. Now its exactly the same state. I figured getting a pro in was the best thing to do as they'd sort it quickly rather than me take time off work I'll be going up to clear it up myself now.

This house is made from Yorkshire sandstone delph walling, the house next door has been sandblasted. The pointing is way to strong for the stonework, eventually this strength of mortar will destroy the stonework with freeze/thaw, you can’t see all of the chimney, he needs to get up to the roof to have a proper look.

I lived in a house for 25 years ...had the same problem . Had all the local roofers take a look and spent thousands. Had it repointed ....new flashing and water seal . It was still leaking when I moved house !

My chimney was leaking when it rained due to the bricks being very porous so I tried a version of siloxane yogurt stuff which worked a treat. The bricks in the loft were soaked previously but are bone dry now.

Check,back gutter for leaks,rake out and repoint chimney with weather struck joints,make sure top and corbel course are correctly flaunched,cap and vent any unused flues and maybe hack off internal gypsum plaster and use lime instead? Hope that helps?

I've also noticed the gaps in the fibre cement slates, depends on where he lives & which way his house is pointing he could have water being pushed up under those slates. basically like a capillary action. If he finds that most of the time the wind blows over this side of the roof then there's your problem.

Normally I would be critical of siloxane treatments as I am not convinced they are a good idea, however I have used them in a very localised manner and found they can work where all else fails. My advice is don't go to the siloxane as a first port of call as repointing in lime should work, but as you say it might need a bit more help? A point worth making is that traditionally chimneys were always in use and this kept them dry, but today they are rarely used and just get wetter.

Could need a lead tray in the chimney and repointing in lime also vents in the chimney would help

I think the pointing could be on top of the old pointing and not deep enough, also is the flaunching on top of the chimney in good condition as this can let water down through the brickwork, is the chimney being used ? if not it must be vented and a good covering of a water repellent will help with cowls on the top of the pots as well

Might try this storm dry on my chimney. I'm not going up on a roof though, I'm going to use a paintbrush with a really long handle

I agree with you, the chimney has had various efforts but attention to detail is the key, the pointing is hard sand/cement (I would use lime mortar) and lead mate in the flashings is good as it dosnt crack with the movement of the lead during temperature change but I would like to see it fill all the joint (look a bit inconsistant/ gappy) as theres no damp course in this I would plumb for sealing it with storm guard or similar and make sure the flaunching is sound on the top with no cracks and fit a vented cap if not in use. You have to remember these bricks have seen it all in terms of "weather battering" and are likley to be very weathered. Chimney is only single skin with a draught going through it (if its an open fire place) so vent it and seal it I aggree. You shouldnt have any more issues. 👍

New lead work is needed, new front apron side flashing and back tray are needed

Hi Roger, Are the chimneys still open and allowing rainfall to enter? Are the fireplaces closed up? You know the rest. Love the channel

Is there a lead tray within the chimney? Stepped lead flashings are designed to protect the junction of the brickwork to the adjoining tiles. They do not stop wet bricks allowing water to pass down into the roof void, this is the job of the tray.

I’d say there’s an issue in the leadwork behind the chimney, water is pooling on the plasterboard at the back of the chimney and then running down the side of the chimney, the watermarks tell the story. If the chimney was allowing water to permeate through there would be a more even spread of a visible damp patch and watermarks whereas in this occasion it is concentrated at the back of the chimney and then finding it’s way down the ceiling alongside the chimney.

My sisters house has a small window on the gable end for the landing , it has a brick arch outside and a wooden lintel inside. When it's been raining for a few days it leaks inside because there is no cavity tray to divert the water that has soaked through the bricks back out so it drips inside. It needs a new lintel and cavity tray but she doesn't want to pay for it .

I wonder if the chimneys blocked off with no air vent You can get condensation building up inside the chimney stack what do you think? Open it up and get some airflow

Sorry Roger - not bricks... Yorkshire stone. I had the same problem with my back gutter. Replaced it, but still got water seeping in when the wind drives the rain against it. My chimney is brick. Eventually I gave the whole chimney a coat of that silicone cream. That solved it.

Quite a few things could be happening there, hard to say from brief pics, but maybe even water flowing along the ridge under the tiles from a neighbouring roof? I think I'd try a process of elimination starting by tying a tarpaulin tight around the chimney to see if the water is really coming from there? Though repeat visits will get expensive for the builder, I suspect, as people like an instant correct answer.

There are no caps on 5hose crown type chimneys! The water pours in , hits an internal shelf and there it is , but there's sometimes multiple issues

The chimney on the right hand side is also pointed in the same way, Probably a pin hole, or tiny crack in the lead at rear of the stack dripping on to the timber support board beneath. Lead goes thin when beaten to stretch around a right angle ,plus age and degradation. Staining on the ceiling is mainly to rear and tracking down part way.

We have had chimney scaffold up for two years. Had the pots capped, pointing repaired, stormdry applied. Still a slight damp issue. All the lead looks good. My neighbour and myself are wondering if the lead valleys have become porous. The house is 80 years old. However, it's an ex council property and the council replaced all the roofs in the 70's and sprayed foam insulation into the cavities. Next step is to check all the copper pipes in the loft. Work has been done and we know that in the 70's cheap impure copper was the only tube available and it was contaminated with particles of iron. The iron rusts and small pinholes appear. It's been a nightmare.

Sounds like very sensible advice to me as all external finishes should allow evaporative drying as you rightly point out. Also he should indeed follow your advice an have the back-gutter checked. If the flues are disused I might also suggest fitting pepper pots to these to prevent rain going down the pots. Rain-hoods would be an alternative if they are in use. That pointing is wrong practically and visually as you say!

Cheers Roger, the bricks look like kiln hand casted with the oxygen holes on the faces. These are hard but porous over time. Rebuild with new lead I’m afraid.

The culprit is that pointing job! Someone used a strong mix of cement mortar and cement will retain water for a very long time. Also as @MrDimensionalStone said the pointing is way to strong for the stonework, so it will crack over time and water seeps in. He probably has the same problem in outer walls but insulation prevents from going to inner walls. He should also check the top (flat part) of the chimney. I live in Portugal and for many years people used to restore old houses with granite walls repointing with cement mortar. This led to problems with water ingress and cracking. These days we use lime mortars compatible with the stone.

Easiest thing would be to take down the damp plaster area and expose the chimney from the inside. Dry the timber and wait for the next rain fall, find the exact spot where the water is coming in.

It’s definitely the chimney back gutter area. Also with those particular slates you need 2 eaves! ( one is to hold the copper rivet) ive done lots of Rivendale jobs. I’ve also seen many of them done wrong with regards to riveting. Where is the job? I’m bolton based but do lots of work Burnley way..

Got a leaky chimney possibly and it’s been given plenty of coatings of modern stuff. Hoping I can get a builder to use lime for rebuilding the chimney.

Worked on these for years. Its the soakers they aren't overlapping they aren't long enough. The flashing isn't overlapping enough too. Agree with the storm dry on these old stone houses they have been up 120 years sometimes every little helps. Should see lead poking out of every slate at the side of the chimney

Lots of logical comments been made already, but the colour of the staining indicates mineral contamination which is probably very hygroscopic and possibly will never dry. I’m a damp surveyor and I see this hygroscopic damp problem a lot below old chimneys. I’ve seen perfectly good chimneys removed completely and tiled over, but the damp patch below still never dries. I think it could be part of the issue here.

It isn't just to strong a mix it isn't weather struck, the top of the pointing protrudes past the line of the masonry and it should "tuck" under it. Aside from that the flashings aren't great and if the chimney isn't used some damp could be internal.

How should you protect poor pointing in the winter, especially so as to not lock in moisture?

Could be water going down the chimney pots. A few builders misdiagnosed damp spots around my chimney.. Suggested I needed to scaffold the whole house and take them down. A new £30 cowl fixed it.

Another suggestion: What if that area around the chimney is actually just too cold, allowing condense to form and soak into the gypsum. Like a cold glass in summer. I image that they improved their windows and insulation over the years. What might have started this situation where a house has less loss of heat but therefore less chance to get rid of humidity. In a way, the moisure might be coming from inside the house. Possible or ridiculous?

My first thought was the rear gutter but feel this might be an issue at the ridge. Look how next doors ridge tiles look much more substantial.

I have exactly the same problem! Six different roofers have not been able to fix it. I have a pet paddling pool in the loft catching the water. Am at my wits end after having so much done by different contractors and paid so much. Fed up. How can so many professionals not know what the problem is!

Tray in chimney, pots flaunched, pointing replaced with lime based mortar, professionally made full lead flashing etc. All need assessing. But firstly, check the junction of slates with the adjoining roof, around 0.32, I'd be very worried with the height differential and a full running joint. Water will go in all sorts of directions if heat/wind/absorbent materials are involved. Quickest 'solution' is probably start lighting fires in the hearth.

Roger didn't mention much the other reason that pointing is so bad in this situation- it holds the rainwater. It doesn't alow the water to flow off well so it kind of hangs about on the brickwork much longer than it should. The stack needs everything possible tipped in it's favour if it's not going to leak.

I had a similar issue ... builder up and made a mess of my flashing which was as far as he could stretch basically, to no avail....popped an old camera on a fishing rod and filmed the very top from a safe ladder height, around the pots and found the crack across the cement cap...bought a scaffold tower and fixed it myself...solved. just need to start from the top, not just where you can get to...

Possible water ingress around or through the chimney pot. Wind and rain will push water down any gaps. Possibly a cracked or broken or even missing chimney liner due to an chimney fire in the past or dodgy work

Well I never knew about upper damp courses in chimney stacks. 👍

When are we going to have a new series, like when we had James. We need a new extension ore a big renovation. Love the channel.

I live in a cottage built in 1820, water running down chimney in loft. The bricks were soaking water like a sponge. Stormdry solved the problem. Fantastic stuff. Goes on white and creamy but soaks in and then after a day or two you'd never know it was on.

Looks to me like Bradford / Halifax / Keighley area. I suspect the soakers and back gutter. As built these had a very narrow & sloping back gutter, so when you replace the slates you can't just bang in new lead, it needs new wood under to support it too. It looks to me like the rear gutter has just been 'bossed' that's to say formed by hammering it, rather than lead burning (welding) it. I suggest get a proper roofer to strip the slates then replace & / or inspect the soakers making sure they are fixed to the batons and are the correct height & width. The step flashing front corner requires replacement as does the pointing, as mentioned. Lastly the back gutter may need removal for full inspection as even pin holes can be enough to cause a problem. The back gutter upstand itself should be covered by a flashing pointed into the stone ( yes, it's stone) at least 4" above the flat part of the back gutter.

i would check the haunching and fillet on the drip course. if the chimney is not use and the fire places are sealed install vents to each flue , also a top hat on each pot would not be out the way. it is important to have a air flow in the flue

I would say a problem with the back flashing. Or wrong instalation of roof felt with water actually coming from further up the roof then depositing at the end of the felt run

It's worth looking at the ridge tiles close to the chimney

Seen same problem..the entire stack looks saturated due to the pointing actually channelling rain in and poor silicon job - it will refuse to dry without some help! Solution was to rake it right back, check soakers etc then put a temp breathable roof felt covering over it and make sure its venting well then let it dry out over summer. Once dry weather struck point with soft lime mix

Different ridge on from next door 0.38, tiles split (property join) down middle of chimney by the looks as well. Plenty things to look at 😂 and guess, not enough detail from the pics.

Should have inspected the capping and the pot bedding ,the damp could well originate from the stack core which once saturated would exude moisture to the interior for some time.

The pointing is the issue more than the type of sand and strength they have used. Pointing should sit just under the brick above it and chamfered to create run off. That pointing is trapping rain water at the top of the pointing due to it coming out further than the brick.

Hi Roger, in a couple of other beating the damp video you used those chemical stick that leach a sealant into the bricks would those work here if the cement mortar is racked out the sand and lime used to replace with these stick set in to make a barrier deeper into the brick work?

Is the cement round the pot cracked?

Just a thought, but if the chimney is blocked up, is there adequate venting top and bottom to allow any moisture another route out? Some of the staining looks as though some of the old salts and tar are leeching through the brickwork and along with water wicking it's way down is making the whole thing worse. The traditional cure for the staining was limewash with some cow sh*t mixed in with it!

Look at pic on page 8:09. There you can see each bit of flashing is basically a narrow sheet of lead that barely extends to the left beyond the margin of the next section of flashing. This allows water to creep along in that overlap, then migrate further inwards to the brick. Those sections of flashing should have their entire face be shaped like a triangle with the top going into the mortar, then the next section coming down over it, not leaving unflashed small sections. There lies the source of the leakage problem - bad, incomplete flashing sections..