Damp on chimney wall - hydroscopic salts
Discussion
kurt535 said:
happy to: pm me and i can send through pictures of one I've just done.
one mistake i've constantly seen done is people trying to eradicate damp in old houses (like a new build); candidly you won't. liberal use of blackjack, sika render, sand cement render, dpc injection systems...all will make the situation worse/move the damp problem onto another area where you may not even be able to sort out when it becomes a problem.
the old houses have to breathe. its really vital to understand why the damp is there in the first place and then find a way to reduce/manage it.
It seems in this case the water ingress has been cured but the OP still has the problem with residual salts in the brickwork. How does lime plaster cope withone mistake i've constantly seen done is people trying to eradicate damp in old houses (like a new build); candidly you won't. liberal use of blackjack, sika render, sand cement render, dpc injection systems...all will make the situation worse/move the damp problem onto another area where you may not even be able to sort out when it becomes a problem.
the old houses have to breathe. its really vital to understand why the damp is there in the first place and then find a way to reduce/manage it.
existing salts(even if the brickwork is brushed down)? If you were to lime plaster the affected area then redecorate would you still get the salts coming
through? I'm not knocking your passion for lime plasters etc. indeed I've spent quite few hours looking at their use on You Tube and find the whole subject fascinating, I'm just curious how traditional lime plaster copes with situations like this.
Its the salts part I'm struggling with - I think if I have salts near surface of the wall, the moisture from the room will stick to those salts. Only way to stop salts reacting with the air in room has to be some kind of barrier?
Its likely case that where wall has bricks is ice cold - where rest of room with lath and plaster walls is slightly warmer. Maybe part of the problem?
I expect we have more moisture inside the house these days (compared to when it was built) with hot showers etc. - no issues elsewhere in the house at all though with damp or mould etc. We've not gone too far in making it air tight.
I'm totally on-board with letting house breathe and have avoided use of cement on any pointing etc. using lime. I can see use of vinyl emulsions can be a bad idea.
Will PM you Kurt. Thanks.
Its likely case that where wall has bricks is ice cold - where rest of room with lath and plaster walls is slightly warmer. Maybe part of the problem?
I expect we have more moisture inside the house these days (compared to when it was built) with hot showers etc. - no issues elsewhere in the house at all though with damp or mould etc. We've not gone too far in making it air tight.
I'm totally on-board with letting house breathe and have avoided use of cement on any pointing etc. using lime. I can see use of vinyl emulsions can be a bad idea.
Will PM you Kurt. Thanks.
wolfracesonic said:
It seems in this case the water ingress has been cured but the OP still has the problem with residual salts in the brickwork. How does lime plaster cope with
existing salts(even if the brickwork is brushed down)? If you were to lime plaster the affected area then redecorate would you still get the salts coming
through? I'm not knocking your passion for lime plasters etc. indeed I've spent quite few hours looking at their use on You Tube and find the whole subject fascinating, I'm just curious how traditional lime plaster copes with situations like this.
Lime plaster wouldn't fix the problem with the salts, they'd just come through again as they would with gypsum. For a chimney breast contaminated by years of use you need to treat & isolate it (eg. by dry lining), which is a solution you wouldn't use elsewhere. existing salts(even if the brickwork is brushed down)? If you were to lime plaster the affected area then redecorate would you still get the salts coming
through? I'm not knocking your passion for lime plasters etc. indeed I've spent quite few hours looking at their use on You Tube and find the whole subject fascinating, I'm just curious how traditional lime plaster copes with situations like this.
Yes, people use the wrong solutions to what are usually very simple damp problems and the use of the wrong materials can cause all sorts of damage but lime and 'breathable' materials are not the solution to every single issue.
The heritage industry pushing lime as the solution to everything is just as full of b
ks as the damp snake oil lot. orbit123 said:
I expect we have more moisture inside the house these days (compared to when it was built) with hot showers etc.
I have the opposing view 
Yes we have more moisture now, but they still cooked and bathed in the old days and they didn't have modern central heating to manage the dew point. So I think if bathroom extractors and kitchen extractors are a high quality with overrun, modern heating, dehumidifier if drying clothes aside and so on, it should eliminate most of it.
Lotobear said:
Has anyone used this stuff? i need to address this issue myself and it looks good...I've specified it in flood restoration work.
Yes, it works.
I've not used it for chimney salts but I can't see why it should not work in that application too. Sovereign are very helpful and will be able to provide a bespoke specification for any application or, otherwise, confirm if it's not suitable.
Yes, it works.
I've not used it for chimney salts but I can't see why it should not work in that application too. Sovereign are very helpful and will be able to provide a bespoke specification for any application or, otherwise, confirm if it's not suitable.
IrateNinja said:
Has anyone used this stuff? i need to address this issue myself and it looks good...
Nope but I remember that there is a bloke on the plasterers forum claiming his stuff is better and cheaper: http://www.plasterersforum.com/threads/renderlite....hyphen said:
Nope but I remember that there is a bloke on the plasterers forum claiming his stuff is better and cheaper: http://www.plasterersforum.com/threads/renderlite....
That link came up when I googled the product earlier. Seems a bit too good to be true, but will talk over the options.Out of interest, and not trying to hijack the thread but seeing as the experts are in...
We have the salts coming through the front face of the chimney breast that’s as plastered with the usual orange stuff - presume hard coat and a smooth finish type stuff. The internal alcove of the fireplace also had the same treatment - outside walls of the breast were not done.
The salt only comes through the front face, not the internal part of the fire place - any reason why that might be?
To be honest I’m tempted to just whack some Zinsser stuff on it for the short term, I did use damp rods before plastering but I doubt they do much, so may inject it before having it rendered some time in the future.
We have the salts coming through the front face of the chimney breast that’s as plastered with the usual orange stuff - presume hard coat and a smooth finish type stuff. The internal alcove of the fireplace also had the same treatment - outside walls of the breast were not done.
The salt only comes through the front face, not the internal part of the fire place - any reason why that might be?
To be honest I’m tempted to just whack some Zinsser stuff on it for the short term, I did use damp rods before plastering but I doubt they do much, so may inject it before having it rendered some time in the future.
The 'orange stuff'? I'm guessing you mean Browning backing plaster finished with multi finish. Great stuff that it is, Browning is no good if damp is around or if you have salts present, you really need a renovating plaster/sand and cement with a salt inhibitor or a membrane system. Injecting a dpc or Dryrods/Dryzone is a bit hit and miss with chimney breasts due to their construction. Have you thought about lime
?
?Yeah it’s just bagged stuff like you’d get in B&Q - I used the hardwall when I plastered the bathroom.
I checked with the plasterer if it was the right stuff as i’d Already read it needed to be specific product, presumed he knew what he was doing. Having used him since for something else I know now I was wrong!
Definitely needs an inhibitor in there somewhere. Will probably get it re-done soon as we’re having an extension at the moment so might as well get the plasterer to do this too.
I can always do a DPC at a later date if needed. The skirting board can come off easy enough to get to the mortar course.
I checked with the plasterer if it was the right stuff as i’d Already read it needed to be specific product, presumed he knew what he was doing. Having used him since for something else I know now I was wrong!
Definitely needs an inhibitor in there somewhere. Will probably get it re-done soon as we’re having an extension at the moment so might as well get the plasterer to do this too.
I can always do a DPC at a later date if needed. The skirting board can come off easy enough to get to the mortar course.
Post excavations we all love them..
I appear to be about to find myself in this situation with regards to breasts... Stripping back the breast to masonry & applying a barrier all well and good, so plaster can be applied without migrating salt damage. BUT, the chimney breasts don't have a dpc unlike the rest of the walls (slate), I'm then wondering surely the barrier will prevent that masonry from breathing and obviously affect it's ability to loose moisture? Or am I missing something here?
Possibly dryline if there's space tbf. Would then the cavity behind need to be ventilated @ HL & LL in that case?
Beers
edit: ( Oh wait it can breathe on the chimney side!
)
I appear to be about to find myself in this situation with regards to breasts... Stripping back the breast to masonry & applying a barrier all well and good, so plaster can be applied without migrating salt damage. BUT, the chimney breasts don't have a dpc unlike the rest of the walls (slate), I'm then wondering surely the barrier will prevent that masonry from breathing and obviously affect it's ability to loose moisture? Or am I missing something here?
Possibly dryline if there's space tbf. Would then the cavity behind need to be ventilated @ HL & LL in that case?
Beers
edit: ( Oh wait it can breathe on the chimney side!
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