Wall problems

[Toby Newell]

Tricky one. Wall seems a bit crowded. I read rising damp is vanishingly rare yet I seem to see it quite often. Mostly caused by change in ground levels rather than lack of dpc though in my experience. Think it gets overly poo pooed as it's the rabbited default for lazy surveyors / damp treatment sellers. Silane works better on lime mortar as it's alkali cured, all three silicone based treatments are breathable. They don't have a filling effect, rather just make porosity hydrophobic. Siloxane weathers quicker and penetrates slower if you are worried. Can take a long time to run through the potential list of issues. Start with roof, gutter, windows, pointing, ground levels, run off, run a dehumidifier, allow exterior wall to breath by leaving space around it. Would be wise to let it dry out a little before applying any treatment.

 

[GinnyLong]

I use a wood burner, dehumidifier & underfloor heating. Windows always open a couple of inches.
Thanks for the advice.

 

[Toby Newell]

Well, you are doing all the right things. Just a process of elimination.

 

[stuart45]

One of the other issues with barn conversations is that the walls can sometimes get hygroscopic salts in them from the animals kept in there, or if manure is piled up against the walls. This happened on a barn conversation job years ago, when an internal wall was dot and dabbed and the wet dots brought the salts through to the surface of the plasterboard.

 

[Stevers]

Having experienced the problems that salts (from combustion) produced in a basement chimney breast, I am also wondering of this barn once held animals. I was told that one of our basement walls had salts typical of a midden - our house being on the gardens behind two cottages that had been demolished to build it!

 

[GinnyLong]

Very likely, I would say

 

[Lacan07]

The survey when I bought it said rising damp only.
The staining goes all the way along the adjoining wall. Upstairs is a bit better than downstairs.

Surveyors know jack s**t about rising damp. How high up the wall is the staining?

There's plenty of factors to consider first, as Twig has already suggested composition of the floor is also important, retro-fitted concrete floors can cause problems.

Use of a sealant should be your last port of call, there's a popular product called 'Stormdry' which claims to be breathable.

 

[GinnyLong]

Ok, thanks. I’ll look it up

 

[stuart45]

The problem with products that claim to be breathable, they don't normally have any technical info that tells you exactly how breathable they are. Things that only allow a small amount of air through could still be classed as breathable. There are different methods of measuring how breathable something is, but one is the SD, or Steam Diffusion rate.
Regarding your rising damp, the diagnosis of this is more complex than sticking a damp meter on the walls.
A few years ago Salford University obtained massive funding to study rising damp, and the result of a 4 year study was a 400 page document. A friend of mine sent me a copy, so I felt obliged to read it.
There was a lot of research done into Jeff Howell's book, Peter Ward and his website as well as studies in the lab, properties with damp in the UK and abroad.
The main finding was that rising damp does exist. It's more common in older houses because it can take years for ground salts to affect the walls ability to desorb moisture, which is the main reason that it goes higher instead of evaporating. It's also the reason why Jeff failed in his attempts at getting any rising damp in his piers.
Another mistake he made in his book was the point that any reference to rising damp couldn't be found anywhere before the 50's. He also studied the 1875 Public Health Act and couldn't find any reference to it there as well, so he assumed the DPC was to do with sanitation.
However the researchers found that although he was correct about it not being mentioned there, it was found in reports from the British Medical Journal in 1875 where it mentions the health issues caused by rising damp a number of times and the need for a DPC.

 

[GinnyLong]

Hmm interesting

 

[Toby Newell]

The problem with products that claim to be breathable, they don't normally have any technical info that tells you exactly how breathable they are. Things that only allow a small amount of air through could still be classed as breathable. There are different methods of measuring how breathable something is, but one is the SD, or Steam Diffusion rate.
Regarding your rising damp, the diagnosis of this is more complex than sticking a damp meter on the walls.
A few years ago Salford University obtained massive funding to study rising damp, and the result of a 4 year study was a 400 page document. A friend of mine sent me a copy, so I felt obliged to read it.
There was a lot of research done into Jeff Howell's book, Peter Ward and his website as well as studies in the lab, properties with damp in the UK and abroad.
The main finding was that rising damp does exist. It's more common in older houses because it can take years for ground salts to affect the walls ability to desorb moisture, which is the main reason that it goes higher instead of evaporating. It's also the reason why Jeff failed in his attempts at getting any rising damp in his piers.
Another mistake he made in his book was the point that any reference to rising damp couldn't be found anywhere before the 50's. He also studied the 1875 Public Health Act and couldn't find any reference to it there as well, so he assumed the DPC was to do with sanitation.
However the researchers found that although he was correct about it not being mentioned there, it was found in reports from the British Medical Journal in 1875 where it mentions the health issues caused by rising damp a number of times and the need for a DPC.

Rising damp obviously is a thing I see it very regularly, in fact the worst damp I see affecting floors is rising damp, from piers and / or from bridged dpc due to high ground levels and / or splashback. To deny rising damp is to deny capillary action. These reactionaries are throwing the baby out with the bathwater simply because uneducated surveyors and uneducated and duplicitous damp treatment companies misidentify a lot of other damp pathways as rising damp. After I last mentioned this I took photos of my very next job which had rising damp! Caused by splashback from an excessively high driveway slab and blocking of airbricks.

 

[Toby Newell]

Also...

Microporous (branded as breathable) acrylic masonry paint – 0.5 (50cm) SD – 180g/m²/day
Stormdry masonry cream (silicone) – 0.35 (35cm) SD – *
Emperor Masonry Creme (silane) – 0.03 (3cm) SD -* **
Beeck SP Plus sealer (Silane and Siloxane) – 0.03 (3cm) SD – *
Limewash – 0.01 (1cm) SD – 1968g/m²/day

But please check every product.

How breathable are masonry sealants? - Truscott Building Preservation

How breathable are masonry sealers? The science of breathability Before we can begin to discuss how 'breathable' or 'non-breathable' a material or product is, we first need to understand four very important factors. 1: The science of 'breathability' in building materials The correct...

truscottpreservation.co.uk

It can be very hard to discern BS unless you have a good background in science and engineering.

 

[Toby Newell]

Surveyors know jack s**t about rising damp. How high up the wall is the staining?

There's plenty of factors to consider first, as Twig has already suggested composition of the floor is also important, retro-fitted concrete floors can cause problems.

Use of a sealant should be your last port of call, there's a popular product called 'Stormdry' which claims to be breathable.

SD 0.35 Yes, slabs are often a cause of issues too. On a hill near a coast is a big risk factor for direct wetting.

 

[Stevers]

I'm a little wary of the source, but this document does attempt to list some of the different salts found in buildings:
https://www.property-care.org/write/MediaUploads/resources/PaulasPaper1TypesandSourcesofSalts.pdf

I had assumed sulphates in chimneys, nitrates from animals, chlorides near the sea, but it's more complicated than that, especially as the salts can be compounds. It's interesting that one of the salts found in chimneys is our old friend (not) gypsum... Any building that has held animals (unless house trained) is likely to have a head start when it comes to the accumulation of salts that can lead to rising damp.

As to a possible solution: One of my splayed window reveals at around eye height was salting heavily despite being well above ground level (though it is close to tanking with modern gypsum plaster), so in January I dug out the old lime plaster and refinished it in NHL plaster. At that time of year it took about four weeks to dry, with minimal salting at the end of the drying process, and it seems to be OK now. My Doulting Stone basement fireplace (limestone) did salt heavily after it was re-installed, but the salting reduced over a few months and has now stopped. This experience would suggest that brushing the salts off and disposing of them might reduce the salt levels in a wall potentially to a level where salting stops, but I can't imagine any sort of paint finish surviving that level of abuse. One way forward would be to remove the presumably modern paint that has failed. If the wall is pointed in cement you'd want to repoint in lime (NHL will do), and you could even go on to apply a self colour lime plaster for a less bucolic look. Without damage to the new finish you should then be able brush the salts off until the salting stops, and at that point you might get away with a clay paint that would keep the surface dry enough to prevent further salt movement - at least until some idiot slaps a coat of Vinyl Slyk on it.

 

[GinnyLong]

What does nhl stand for please? I hoover the loose salts of every few days. Thanks for the suggestion of clay paint. I did wonder if that would help. Once it’s dried out enough

 

[Stevers]

NHL is Naturally Hydraulic Lime, there are lots of references to it on this forum. I buy mine from one of the independent builders merchants, and check that whichever brand is currently in stock there is cement free. I used a very rich mix with fine sand to make my finishing plaster, and that was salting freely without the surface being damaged, although there was a teeny bit of shrinkage. For base coats or pointing 1:3 should do - the aggregate can be 50/50 of soft and sharp sand. Tanking would just leave it cold and wet, and short of adding an inner leaf, insulation, cavity, DPC etc. I am wondering what else you could do with it.

This is the saga of my basement chimney breast (with that fireplace surround) that has dried out a treat from very unpromising beginnings:
https://www.periodproperty.co.uk/forum/threads/basement-chimney-breast.17787/

 

[GinnyLong]

Thank you

 

[stuart45]

NHL comes in different strengths. 2 is the softest, and the closest to an air lime. 3.5 is a bit stronger and often used for exterior pointing. 5.0 is stronger again and often used for limecrete floors.

 

[aockenden]

What are all the layers of coating on the inside walls where you’re getting the staining? You mentioned that you painted over it with limewash, what were you painting ontop of? What’s underneath that? All the way back to the underlying stone / brick.

 

[GinnyLong]

The brick shows streaks but doesn’t feel damp. I wonder if they were coated in unibond pva. Walls don’t feel damp either, I can’t tell what they were painted with before me.