Another Damp Stone Wall, Please Help!

[G_amsonad]

Hi, I am a new member. I have read several threads on this forum already and I’m hoping someone might be able to help me out? I would be very grateful for any input.

I bought my house in June 2023 and one section has problems with damp. It is solid stone wall construction, with concrete render externally and internal gypsum plaster. The house is in Northern Ireland (aka its wet). The finished floor level is only slightly above the external floor level. The worst affected walls face south and west. It’s a very exposed site so they take the brunt of the prevailing southwesterly winds. We have had our builder, architect, surveyor and a PCA damp surveyor look at the property. Consensus is that penetrating damp is occurring via inadequate flashings, a disused chimney breast and through small cracks in external render. Condensation is also an issue, which will address by installing extractor fans in bathrooms. Some have suggested a PIV system to aid ventilation further.

Each person has a different opinion on how to address this problem. The PCA member suggested considering a French drain externally, re plastering internally with lime and ideally also replacing the external render in lime. They also suggested the use of an injectable DPC in a couple of areas which I have to say I don’t really buy into.

Our architect suggests using an insulated stud wall and ventilating the void via the attic. I initially was quite keen on this idea, but the PCA member advised that by making the stone wall colder, interstitial condensation would become worse and there could be a problem of damp in the void, damaging the back of the stud.

The builder suggested a DPM (Newton CDM / Visqueen type system) attached onto the internal surface of the stone wall. Then a metal stud system with foam insulation in the void, but we are not keen on foam insulation and again there is the problem of condensation on the stone wall.

A final suggestion was to dry line the wall, again using a metal stud, but not to use insulation and to ventilate the void into the room itself. The theory being that this would avoid making the stone wall colder and worsening condensation.

Everyone can point out a flaw in each of the other plans. Obviously I know that there is perhaps no ‘right’ or ‘perfect’ answer. The lime solution is rejected by most people we have spoken to, saying its fine in sunny SE England but no here in Ireland. But it must be used successfully in equally wet areas of the UK?

Finally, my wife is concerned about lime houses just being damp e.g. it doesn’t fix the problem but the material can just withstand the dampness better. Is this true or are lime rendered houses dry and comfortable?

Apologies for long post, look forward to any pointers!!

Gregor

 

[aockenden]

We’re in very wet central Wales. We had a soaking wet, thickly cement rendered western gable wall when we bought the place 2.5 years ago. After stripping off all the cement externally and re-rendering the wall in lime, it’s dried out wonderfully. You can watch the moving moisture patterns as the wall releases its moisture after heavy driving rain. It doesn’t take much sun and wind over the walls surface to properly dry it out again.

 

[G_amsonad]

Hi Aockenden,

Thanks for the reply. Regarding living in a lime rendered/plastered house- is it the case that you can see damp patches appearing for example during periods of rain, but that they disappear rapidly once better weather arrives and that it doesn't leave lasting damage/marks to the decorative finish? And I'm assuming the room won't smell damp?

Any other input into the proposed stud wall systems would be gratefully received! I'd also like to hear peoples thoughts as to whether putting lime plaster internally is a waste of time if external render is left as concrete e.g. at least the wall can 'breathe' on one side, even if ideally it would be able to breathe on both sides.

Thanks

Gregor

 

[aockenden]

Hi Aockenden,

Thanks for the reply. Regarding living in a lime rendered/plastered house- is it the case that you can see damp patches appearing for example during periods of rain, but that they disappear rapidly once better weather arrives and that it doesn't leave lasting damage/marks to the decorative finish? And I'm assuming the room won't smell damp?

Any other input into the proposed stud wall systems would be gratefully received! I'd also like to hear peoples thoughts as to whether putting lime plaster internally is a waste of time if external render is left as concrete e.g. at least the wall can 'breathe' on one side, even if ideally it would be able to breathe on both sides.

Thanks

Gregor

Yes there are small areas around our windows where moisture can wick through the lime and clay mortars into the inside of the house, but they only occur in heavy sustained driving rain and disappear within a day or two as the capillary system in the lime and clay redistributes and evaporates away the moisture. Those areas do not smell noticeably damp even when they are damps and certainly not at all once they dry back out. They also don’t ruin any finishes / paints as long as they are properly breathable.

Putting lime plaster internally is still valuable even if the outside is still cement rendered. It will help manage condensation issues internally. The “all or nothing” stuff is a fallacy.

 

[G_amsonad]

Hi again,

Thanks for the info. We are considering lime plastering internally first, in the knowledge that if we still have issues we might need to take off the external cement render and replace with lime.
We are still considering studding the walls/internal wall insulation, however any way of ventilating the void seems to have theoretical problems. The thought of condensation in the void is concerning and I do wonder if its just covering up a problem and not addressing it.

 

[elizabeth]

We are in Devon and our cob and stone cottage is at the top of a hill facing south westerly and it can get hammered by rain. Our cottage was encased in cement render and internally it was a mix of gypsum with another layer of cement slurry and the dreaded blackjack (bitumen) 3ft up the wall. The cement render developed fine cracks because the cottage is constantly expanding and contracting depending on the temperatures. The render was rigid and did’nt move. This allowed rain to penetrate behind the render and led to the cob deteriorating and the stones soaking wet.
Soon as we took off the render, the walls started to dry, though of course being very thick, it was a slow process.
We did the lime render by piecemeal as the cost was hard for us. It was suggested in order to help dry out the bottom of the walls and encourage the moisture to wick from inside to outside, we could take the first 12inches of render off the bottom. This could be an option as well as lime inside.
Having lime just inside, as aockenden mentions as well as heating and good ventilation through windows vents, extractors in bathroom and kitchen, you will notice a difference in comfort and reduce the build up of condensation.
Since using lime inside and out, our cottage has been dry and comfortable. We have also learnt to manage the cottage better.
With regards insulation, you may be able to find a write up by Twig on the use of insulating, breathable wood wool boards, directly laid against a stone wall - least that is what I think. There are also other ways such as adding insulating natural materials to lime.


Avoid injection of DPC at all cost.

 

[G_amsonad]

We are in Devon and our cob and stone cottage is at the top of a hill facing south westerly and it can get hammered by rain. Our cottage was encased in cement render and internally it was a mix of gypsum with another layer of cement slurry and the dreaded blackjack (bitumen) 3ft up the wall. The cement render developed fine cracks because the cottage is constantly expanding and contracting depending on the temperatures. The render was rigid and did’nt move. This allowed rain to penetrate behind the render and led to the cob deteriorating and the stones soaking wet.
Soon as we took off the render, the walls started to dry, though of course being very thick, it was a slow process.
We did the lime render by piecemeal as the cost was hard for us. It was suggested in order to help dry out the bottom of the walls and encourage the moisture to wick from inside to outside, we could take the first 12inches of render off the bottom. This could be an option as well as lime inside.
Having lime just inside, as aockenden mentions as well as heating and good ventilation through windows vents, extractors in bathroom and kitchen, you will notice a difference in comfort and reduce the build up of condensation.
Since using lime inside and out, our cottage has been dry and comfortable. We have also learnt to manage the cottage better.
With regards insulation, you may be able to find a write up by Twig on the use of insulating, breathable wood wool boards, directly laid against a stone wall - least that is what I think. There are also other ways such as adding insulating natural materials to lime.


Avoid injection of DPC at all cost.

Thanks Elizabeth

As a cost saving measure, it has been suggested to us that we could use a masonry cream over the existing cement render in order to try and seal any cracks and reduce water ingress. Hopefully the internal lime plaster and improved ventilation via PIV would allow enough evaporation/breathability of the wall. The only reason this was even suggested is due to the high expense of replacing the existing cement render with lime. I have doubts as to whether the masonry paint would work, as any new cracks in the cement render would also crack the paint and result in new areas of water ingress.

Would be interested in your thoughts on this?

Ideally would go full lime but awaiting estimates of cost and ready for a shock!

Gregor

 

[DaveG]

From what I’ve read (The warm dry home - https://www.periodproperty.co.uk/forum/threads/the-warm-dry-home-new-peter-ward-book.17530/)

chemicals of any kind whether it be injection DPC or coatings are a waste of money.
I think your approach to inside first will definitely improve things a great deal. I kind of think of it like the money box analogy. Just a small slot and even if you just add the odd coin here and there it accumulates. Much like damp that’s entered a hairline crack, you’ll struggle to empty those coins back out from the same slot they went in so it just accumulates.
Going to a breathable material on the inside will give that damp a nice big area to evaporate from and provided you have good airflow indoors it will be taken away as vapour nicely. I’ve seen this recently where a friend of mine bought a former pub where the rear wall is actually built into the side of a hill. The earth up against that wall is constantly damp and when he moved in, water was streaming down the rendered wall.
Fast forward 2 years, he took it all back to the stone and lime pointed and the wall feels dry. It’s become a transportation layer for water to evaporate off instead of a leaky damn of concrete

 

[G_amsonad]

From what I’ve read (The warm dry home - https://www.periodproperty.co.uk/forum/threads/the-warm-dry-home-new-peter-ward-book.17530/)

chemicals of any kind whether it be injection DPC or coatings are a waste of money.
I think your approach to inside first will definitely improve things a great deal. I kind of think of it like the money box analogy. Just a small slot and even if you just add the odd coin here and there it accumulates. Much like damp that’s entered a hairline crack, you’ll struggle to empty those coins back out from the same slot they went in so it just accumulates.
Going to a breathable material on the inside will give that damp a nice big area to evaporate from and provided you have good airflow indoors it will be taken away as vapour nicely. I’ve seen this recently where a friend of mine bought a former pub where the rear wall is actually built into the side of a hill. The earth up against that wall is constantly damp and when he moved in, water was streaming down the rendered wall.
Fast forward 2 years, he took it all back to the stone and lime pointed and the wall feels dry. It’s become a transportation layer for water to evaporate off instead of a leaky damn of concrete

Hi Dave,

Thanks for another helpful reply!

Does the same apply re floors? The concrete screed in the affected room is damp. Would replacing with limecrete be beneficial? Limecrete is something I've only just come across.

Thanks again!

 

[aockenden]

Hi Dave,

Thanks for another helpful reply!

Does the same apply re floors? The concrete screed in the affected room is damp. Would replacing with limecrete be beneficial? Limecrete is something I've only just come across.

Thanks again!

Yes it would be beneficial

 

[DaveG]

I’m on a big learning curve the same as you as I only bought my stone walled house 2 months ago. I will say that book is a worthwhile investment as are Peter Wards YouTube videos (no affiliation, just personal experience).

What you’re going through sounds partially similar to what I have although the stone on the outside of my home is still exposed and it’s from the inside the damp man has caused all the problems.
I have the dreaded concrete slurry and gypsum plaster up to 1.5m all around which I’m very slowly removing again. From 1.5m up it’s still original lime plaster (and bone dry!)

Regarding your floor question, in my own case I still have the original air vents on the outside walls for what was originally suspended wooden floors. These no longer function since damp man filled the floor with what I presume will be hardcore before adding a dpc and an inch or so of scree.
In my case the floor is dry but I’m sure the dpc is just displacing the damp from the ground to its edges and soaking the walls.
I think my plan, not for the faint hearted, is to dig it all back out and go back to suspended floor. In my personal case this is because the hallway which sits right in the middle of the floor plan is still suspended whilst it appears everything around it has either been filled in with concrete or is an extension, meaning there’s nowhere to get ventilation to this area of the floor.
Depending on the wider situation though, others on here have had success just taking out a few inches of the concrete floor all around the perimeter of the room and replacing with limecrete.
I think the problem is that every case is different. Where are you finding the floor to be damp? Is it just at the base of the walls or further into the centre of the room?
Do you have any evidence that perhaps your floors were once suspended too?
Its good if you can try to build that picture of how the house would have been originally before trying to rectify

 

[G_amsonad]

I’m on a big learning curve the same as you as I only bought my stone walled house 2 months ago. I will say that book is a worthwhile investment as are Peter Wards YouTube videos (no affiliation, just personal experience).

What you’re going through sounds partially similar to what I have although the stone on the outside of my home is still exposed and it’s from the inside the damp man has caused all the problems.
I have the dreaded concrete slurry and gypsum plaster up to 1.5m all around which I’m very slowly removing again. From 1.5m up it’s still original lime plaster (and bone dry!)

Regarding your floor question, in my own case I still have the original air vents on the outside walls for what was originally suspended wooden floors. These no longer function since damp man filled the floor with what I presume will be hardcore before adding a dpc and an inch or so of scree.
In my case the floor is dry but I’m sure the dpc is just displacing the damp from the ground to its edges and soaking the walls.
I think my plan, not for the faint hearted, is to dig it all back out and go back to suspended floor. In my personal case this is because the hallway which sits right in the middle of the floor plan is still suspended whilst it appears everything around it has either been filled in with concrete or is an extension, meaning there’s nowhere to get ventilation to this area of the floor.
Depending on the wider situation though, others on here have had success just taking out a few inches of the concrete floor all around the perimeter of the room and replacing with limecrete.
I think the problem is that every case is different. Where are you finding the floor to be damp? Is it just at the base of the walls or further into the centre of the room?
Do you have any evidence that perhaps your floors were once suspended too?
Its good if you can try to build that picture of how the house would have been originally before trying to rectify

Sorry for the delay in replying, other things including garden needing attention!

I've not got round to lifting all the floor covering (carpet) yet, but that seems like the obvious place to start so I can fully assess which areas are damp. I found an old thread from this site (https://www.periodproperty.co.uk/fo.../#:~:text=If you're after an,if you're listed!) that as you mention suggests it may be possible just to do a limecrete the border if the rest of the floor is dry. Obviously lifting the floor and re-doing it all in limecrete may be ideal and allow insulation to be added, but I think unless we have to change the floor due to the whole concrete screed being damp it might not be worth the hassle in our case, or even possible with our budget.

I've spoken to two lime plasterers since starting this thread. Neither have been out to the house yet, so take it with a pinch of salt, but one suggested the house would need the concrete render replaced with lime as well as being plastered with lime internally, whereas the second said if he had to prioritise replacing either the plaster or render in lime, he would pick the render- which contradicts what the previous damp surveyor suggested as discussed on earlier posts...

Should be getting them out to visit soon which hopefully will shed more light on things, including costings etc. Will keep the thread updated when I hear more.

Thanks again

Gregor

 

[ShelleyM]

Hi Gregor

Any further updates re removing the render , Im interested to hear what you have been advised to do?

Thanks

S

 

[G_amsonad]

Hi Gregor

Any further updates re removing the render , Im interested to hear what you have been advised to do?

Thanks

S

Hi Shelley,

No updates yet, but a lime plasterer is visiting this Friday so I will keep you posted after I've heard what they have to say.

Regarding the floor, I've lifted the carpet to reveal the screed. It appears to have a black paint, which I presume to be a paint based DPM, applied up to about an inch or two from the base of the wall. Can only guess this is not ideal. However it does appear to be flaking in places so hopefully it might not be difficult to remove. Will be asking re limecrete flooring on Friday also.

All the best,

Gregor

 

[ShelleyM]

Thanks Gregor

Can you pass me on the details of the lime plasterer please

 

[CassCottage]

Hi, I have just come across your thread and I have been looking into a similar situation, I found this website to be really useful - I have no experience of using them, although I have asked for a quote to do a survey. They have lots of sensible advice regarding damp and also back up what others are saying about not having anything injected. It seems that most problems are caused by using modern materials on old buildings that need to breathe. https://www.heritage-house.org/stuf...on/insulating-an-old-house-breathability.html

 

[G_amsonad]

Hi again,

Shelley- I've sent you a private message of the plasterers details.

Thanks Cass Cottage, I've read a wee bit from that site before but really should revisit it for more information.

Update on the visit today from the lime plasterer/ restoration builder today- pleased with how things went. Their suggestions are:

1.) Strip the cement render and replace with lime
2.) Install a French drain, offset from the base of the wall by approx 500mm to reduce risk of disturbing shallow/non-existent foundations
3.) Possible replace the perimeter of the internal floor cement screed with limecrete

They seemed less concerned about replacing the internal gypsum plaster immediately, however I think if finances allow we will do it at the same time, as we'd rather get as much disruption out of the way in one project if possible.

The builder and architect had made a plan for replacing the decayed joists whereby 3 steel beams would be inserted into the stone walls and then wooden joists would span between these, the theory being that by not having wooden joists directly in the stone wall they will be less susceptible to decay. The restoration builder suggested this would not be necessary if the lime system was put in place, as the timbers would not be damp for prolonged periods due to the property being able to breathe again. He had no issue with the steel beam system, but thought it was probably excessive and unnecessary. I see his point, however I would be interested in what other on the forum think of this argument?

He admitted himself he is a bit of a purist, so would rather change as little as possible with the building and preserve the original fabrics. However, I can see the benefit of avoiding wood being bedded in the stone wall, but perhaps I'm being too cautious?

All the best,

Gregor

 

[aockenden]

Hi again,

Shelley- I've sent you a private message of the plasterers details.

Thanks Cass Cottage, I've read a wee bit from that site before but really should revisit it for more information.

Update on the visit today from the lime plasterer/ restoration builder today- pleased with how things went. Their suggestions are:

1.) Strip the cement render and replace with lime
2.) Install a French drain, offset from the base of the wall by approx 500mm to reduce risk of disturbing shallow/non-existent foundations
3.) Possible replace the perimeter of the internal floor cement screed with limecrete

They seemed less concerned about replacing the internal gypsum plaster immediately, however I think if finances allow we will do it at the same time, as we'd rather get as much disruption out of the way in one project if possible.

The builder and architect had made a plan for replacing the decayed joists whereby 3 steel beams would be inserted into the stone walls and then wooden joists would span between these, the theory being that by not having wooden joists directly in the stone wall they will be less susceptible to decay. The restoration builder suggested this would not be necessary if the lime system was put in place, as the timbers would not be damp for prolonged periods due to the property being able to breathe again. He had no issue with the steel beam system, but thought it was probably excessive and unnecessary. I see his point, however I would be interested in what other on the forum think of this argument?

He admitted himself he is a bit of a purist, so would rather change as little as possible with the building and preserve the original fabrics. However, I can see the benefit of avoiding wood being bedded in the stone wall, but perhaps I'm being too cautious?

All the best,

Gregor

Well all those suggestions / plans are rooted in sensible thinking which is a good sign that you’ve found reasonable logical people who understand old houses and moisture. As for the debate on bedding the steel beams into the wall instead of wooden ones, it’ll probably be fine either way. Our wooden floor joists from a renovation in the 60’s are bedding directly into the stone wall and are both cemented in and covered with impermeable bitumen “damp-proofing” fabric. They are in surprisingly good condition all things considered, including one which had an internal plumbing leak right above it.

 

[Helen Touzeau]

Hi, I am a new member. I have read several threads on this forum already and I’m hoping someone might be able to help me out? I would be very grateful for any input.

I bought my house in June 2023 and one section has problems with damp. It is solid stone wall construction, with concrete render externally and internal gypsum plaster. The house is in Northern Ireland (aka its wet). The finished floor level is only slightly above the external floor level. The worst affected walls face south and west. It’s a very exposed site so they take the brunt of the prevailing southwesterly winds. We have had our builder, architect, surveyor and a PCA damp surveyor look at the property. Consensus is that penetrating damp is occurring via inadequate flashings, a disused chimney breast and through small cracks in external render. Condensation is also an issue, which will address by installing extractor fans in bathrooms. Some have suggested a PIV system to aid ventilation further.

Each person has a different opinion on how to address this problem. The PCA member suggested considering a French drain externally, re plastering internally with lime and ideally also replacing the external render in lime. They also suggested the use of an injectable DPC in a couple of areas which I have to say I don’t really buy into.

Our architect suggests using an insulated stud wall and ventilating the void via the attic. I initially was quite keen on this idea, but the PCA member advised that by making the stone wall colder, interstitial condensation would become worse and there could be a problem of damp in the void, damaging the back of the stud.

The builder suggested a DPM (Newton CDM / Visqueen type system) attached onto the internal surface of the stone wall. Then a metal stud system with foam insulation in the void, but we are not keen on foam insulation and again there is the problem of condensation on the stone wall.

A final suggestion was to dry line the wall, again using a metal stud, but not to use insulation and to ventilate the void into the room itself. The theory being that this would avoid making the stone wall colder and worsening condensation.

Everyone can point out a flaw in each of the other plans. Obviously I know that there is perhaps no ‘right’ or ‘perfect’ answer. The lime solution is rejected by most people we have spoken to, saying its fine in sunny SE England but no here in Ireland. But it must be used successfully in equally wet areas of the UK?

Finally, my wife is concerned about lime houses just being damp e.g. it doesn’t fix the problem but the material can just withstand the dampness better. Is this true or are lime rendered houses dry and comfortable?

Apologies for long post, look forward to any pointers!!

Gregor

Hello, I am a new member restoring /reconstructing a farmhouse in Czechia. I have stone and rubble walls (800mm thick) plus cement external rendering and concrete floors. So all moisture was pushed into the walls. Cement external rendering is a major problem as it prevents the walls breathing. All was removed and I have lime with cork and natural earths plastering internally. I also took out all the concrete flooring and replaced with limecrete. I haven't re-rendered the outside walls but a friend is using a lime plaster bulked with foamed glass beads as the surface is very irregular. Cement rendering is always the problem

 

[G_amsonad]

Hi again everyone,

Thought I would do an update on our house.

As lime was going to be such a big part of the project (including financially) we had another lime plasterer out to look at the house and give a quote. Interestingly, after seeing the house they prioritise stripping off the internal plaster and repointing the wall in lime, using a French drain externally, replacing the whole concrete floor with limecrete, and possibly leaving the cement render in place. They weren't a huge fan of the limecrete border method for the floor.

It is very hard to know what to do. They said themselves, the best way to ensure a fix is to replace the render, plaster and floor with lime and to use a French drain externally. But of course this is expensive. It is interesting that compared to the previous lime plasterer, they seem to prioritise the floor and internal plaster whereas the last person prioritised the external render being replaced with lime.

The lime floor came up quite late in the day in terms of my reading about this, but the more I think about it, it's probably a good idea. A damp floor can't be good for the warmth of the house and replacing the floor with lime would be a good chance to install insulation in the floor and possibly even underfloor heating.

At least they both lime plasterers agree on the use of a French drain, so that's definitely going to be done.

All the best,

Gregor