Dot and Dab Plasterboard on original barn walls causing problems

[lukebasterfield]

This is my first post, after having found this forum through looking for advice on old buildings!

We brought a new house back in February which is a conversion of old farm buildings, arranged in an L shape. One side of it, used to be a pig sty, and we had noticed some problems with what look like damp patches on some of the interior walls in this area. The walls are plasterboard straight onto original brick work (dot and dab), which was the dividing walls for the pig sty (and I imagine used to be exposed to the elements prior to the conversion), and only go up to about 6ft, and divide the internal space. Interestingly, all of the exterior walls seem fine.

We were advised that these damp patches are likely to have been caused by salts in the walls, probably due to the fact is used to house animals, and moisture in the area was being attracted to the plasterboard, and where the dabs have been placed, the salts have migrated to the surface of the plasterboard.

Based on this, I was expecting to pull the plasterboard off, attach a studded cavity membrane such as Oldroyd (which I was advised by a number of damp companies), and put plasterboard back on to stop any future salts migrating through to the plasterboard.

In addition, I was planning to put in some PIV ventialtion to increase airflow, to prevent any condensation build up that might be attracted to the walls (the property seems to be very airtight, with little airflow in this area), which I believed was causing the issue.

Anyway, I pulled off the plasterboard today on one wall, and was surprised at the sheer amount of salt on this internal wall. I was also concerned that at the bottom of the wall, it seems that a lot of the mortar is missing or has eroded away. The mortar higher up seems ok.

There is also evidence of a DPC having been injected at a lower level just below the floor slab, due to regular drill holes.

I am therefore now wondering what to do, if I am indeed doing the right thing with the membrane, and what I need to do about the gaps in the mortar of the walls. Could this be an issue with cement mortar having been used higher up perhaps? (I dont know that it has, just guessing) instead of lime mortar?

Obviously I dont want to pull the entire walls down if I can help it, and whilst only single storey, I think in places they support the roof beams.

Having just spent all our money on buying what we thought would be our dream forever home, I am trying to make all the necessary repairs myself DIY, but would appreciate any help/advice so I can make sure I am doing the right thing. Is plasterboard onto membrane the best way, or would a lime plaster straight onto the walls be better? What steps should I take to clean/prepare the walls due to the existing salt damage?
Thanks everyone in advance for any help/suggestions!

 

[Zebra]

A picture would be helpful, if you can upload one. If it's your first post it might take a while before you can, initial posts being moderated or something like that. Anyway, how old are those bricks? And how soft? Very old soft red bricks, once degraded and deteriorated with time, have a tendency to become rather porous and to attract moisture up from the ground. If the injected dpc is rather ineffective, as they tend to be I believe, then it may be a case of rising damp. Do the bricks feel or look damp? It could be, alternatively, that the salts already there are attracting moisture from the air. I believe you can buy salt neutraliser to remedy this. How damaging the stuff is to old bricks I'm not sure, I've not used it.
I had a similar problem with bricks approx 300 years old. Not salts, but rising damp.
You are lucky that whoever injected that dpc didn't go the whole hog (ha ha, hog! pigsty! geddit? oh alright then) and apply waterproof plaster up to 1.5m, which would have been harder to remove.
If you can stop the damp at source, it would be a better solution than covering it up with a membrane. Interesting that the external walls don't seem to be affected. Have you been tempted to pull a bit of plasterboard off and have a look?
Once the damp issue is solved, l don't know how much of a problem the residual salts will be in terms of replastering, but I would be looking to do it in lime straight onto the bricks, after repointing in lime where the mortar is missing. This can be a DIY job, lime plastering is great fun. If you like that sort of thing. But first you must make sure there is no damp coming in, or your efforts will be wasted.

 

[Zebra]

Oops. Duplicated post.

 

[paulc]

Once the damp issue is solved, l don't know how much of a problem the residual salts will be in terms of replastering, but I would be looking to do it in lime straight onto the bricks, after repointing in lime where the mortar is missing.

Alternatively, how about fixing Savolit wood wool boards to the wall and then lime plaster over the top. This would help to isolate the salts from the plaster as well as giving a flat surface to plaster on to.

 

[Abi Cott]

Why is the issue only on the internal walls? Salt build up due to animals seems a bit far fetched to me, but if it were the case the exterior walls should be equally effected. Have they been treated differently? Rendered? Is it a case of detecting porky pies rather than pigs?

 

[MatthewC]

Why is the issue only on the internal walls? Salt build up due to animals seems a bit far fetched to me, but if it were the case the exterior walls should be equally effected. Have they been treated differently? Rendered? Is it a case of detecting porky pies rather than pigs?

I agree, that's an important question. Possibly the outer walls are stone not brick? Have they got dot 'n dab as well? I wonder if they have dried out properly as the outer face is open to the atmosphere, whereas the dampness was retained in the internal walls due to the plasterboard?!

I can certainly imagine that animal stalls were used to having copious amounts of water hosed around at regular intervals, which could be why the walls are so damp. As ever, understand the cause before you tackle the symptom!

Matthew

 

[lukebasterfield]

All,
Thanks for your suggestions so far. Ive tried uploading some photos, but unfortunately it just says 'File to Large', even though I have made the pictures a lot smaller (just screenshots), maybe its as I am a new user?

Anyway, not sure about the external walls, I am tempted to remove a section of plasterboard in one of the worst affected rooms to take a look, if its all fine, I can easily put it back.

I am now interested in the idea of using wood wool boards and then lime plater on top. Are the wood wool board breathable? I understand that is the greatest issue here, in allowing the fabric of the walls to dry if they become damp.

I am thinking the main cause of the problem is condensation and lack of air flow rather than anything else. Interestingly, the lowest level of bricks visible where the DPC was drilled in look like more solid engineering bricks, and whilst the mortar has still deterioirated here, the bricks themselves are showing no signs of spalling compared to the 3 layers above.
I am thinking the salt in the walls is attracting any moisture which may have been pulled through via the dabs perhaps. We only moved in 2 months ago, but I noticed the previous owners had the bathroom redone in the last 10 years, however there is no extraction fan installed. Also, the air flow in this part of the building seems particular stagnent, the air feels stail and stagnent, i.e due to lack of fresh air.

I had been suggested to consider PIV as a way of bringing fresh air in and pushing out the stale air. Does anyone have experience of these being successful or any thoughts on any other ventiliation systems?

Thanks.

 

[lukebasterfield]

Does anyone have experience of alternative finishes onto existing old brick walls that would still be breathable? Maybe wood panelling, or even leave the walls exposed, maybe just painted?

 

[Abi Cott]

Does anyone have experience of alternative finishes onto existing old brick walls that would still be breathable? Maybe wood panelling, or even leave the walls exposed, maybe just painted?

I've done a LOT of research on this, but I'm just starting to put it into practice.

Lime plaster breathes. Gypsum and cement based ones don't.

Wallpaper breathes.

Claypaint, lime wash and some distemper breathes

Standard emulsion does not breathe, even the ones that say they do, don't do it very much.

Wooden panelling with the batons isolated with strips of dpm is seriously worth investigating. It's the method I will be using in my dampest areas. Even my mortgage required damp surveyor quite liked the idea.

 

[Kearn]

Does anyone have experience of alternative finishes onto existing old brick walls that would still be breathable? Maybe wood panelling, or even leave the walls exposed, maybe just painted?

really depends on the quality of the bricks and also the rest of the space in case it dominates - I am a big fan of leaving them visible when they are beautiful to appreciate the craftsmanship and tones, but fully appreciate that often faces are shot through incorrect surface covering being removed, palling through moisture and incorrect pointing, people messing over the years and removing / cutting channels etc, or some brick walls were simply never designed to be seen and the bond and finish won't be aesthetically pleasing. getting a beautiful bare brick pointed wall will undoubtedly take the most time and work, but like they say, if a job is worth doing...

if you cover, and want a flatter finish, then lime plaster, and if required breathable insulation, will give you a blank canvas. if the faces of the bricks are ok and a more industrial look will work, then limewash onto the bricks. I haven't experience with limewash, but others on here will give you a view I'm sure, opinions seem to be mixed in terms of effort vs. longevity.

what is the floor covering / roofspace / function of the room etc as these will help with visual choices. for example, I have recently restored a Tudor inglenook, the rear of which is in our entrance hall (old animal shelter). I have also dug out the concrete floor and we are laying brick pavers back down and removing the false ceiling so the room will be 3.5m high with a lovely truss exposed up high. So a lot of brick on show, but it works in the space and is as it should have been. However the walls are also lovely 400 yr brick, but I am lime plastering these once the gypsum is off (I am fortunate that centuries of limewash layers have provided a buffer to protect the bricks from the modern render and it pulls off in satisfying sheets with little/no damage) as it would be too much otherwise to leave them on show and they would visually detract from the chimney stack. However, if those walls were in a different room, with less interesting features, they would certainly be an exposed focal point.

 

[Zebra]

Are the wood wool board breathable?

Yes.

 

[lukebasterfield]

All,

Thanks for all your inputs so far. The areas impacted are a walk way to the bedrooms and the bedrooms themselves. I was thinking I could leave the walkway brick exposed, but for the bedrooms I would ideally like some other finish, that is easily manageable for an average DIYer, yet still breathable.
I have also finally worked out how to attach pictures. I had added 3 pictures showing the one brick wall I have exposed so far showing the salt damage, the spalling to the lower course of brick and the missing mortar.
Any further thoughts would be gratefully appreciated!

 

[Spoilt Victorian Child]

Wallpaper breathes.

I've heard to the contrary of this, and indeed when I pulled back the wallpaper in a damp corner of my lounge, the plaster behind was sopping wet, suggesting the wallpaper was trapping moisture.

What are your findings on breathable wallpaper?

 

[Spoilt Victorian Child]

We brought a new house back in February which is a conversion of old farm buildings...

Won't this problem be covered for 10 years by some sort of NHBC Builder's Warranty which (I think) is mandatory now for builders/developers?

Having said that, did the developer really understand the building to dot and dab such walls like that? And a chemical injection?? You might want an expert in old buildings to explain why that system isn't suitable/working, suggest the remedy, and use the warranty to pay for it?

 

[Abi Cott]

Wallpaper breathes.

I've heard to the contrary of this, and indeed when I pulled back the wallpaper in a damp corner of my lounge, the plaster behind was sopping wet, suggesting the wallpaper was trapping moisture.

What are your findings on breathable wallpaper?

You are probably right to sound a note of caution. Vinyl papers would likely cause an issue due to the plastic coating, but my research suggests traditional papers and lining papers hung using traditional paste are fine.

 

[Kearn]

Wallpaper breathes.

I've heard to the contrary of this, and indeed when I pulled back the wallpaper in a damp corner of my lounge, the plaster behind was sopping wet, suggesting the wallpaper was trapping moisture.

What are your findings on breathable wallpaper?

You are probably right to sound a note of caution. Vinyl papers would likely cause an issue due to the plastic coating, but my research suggests traditional papers and lining papers hung using traditional paste are fine.

I guess this is analogous to saying 'paint breathes' - clay yes, plastic modern gunk, no. I've found various traces of paper as I've pared back walls to the original lime paster, removing gypsum skims, some not all that old, say 1940-60's - none of which seemed to have been doing any moisture retention itself, but then if the 'paper' is in fact some nasty chemical based covering and the adhesive used is similar, then I can't see all wallpaper being breathable... but as the OP is the one applying the covering, then there is obviously the ability to pick a breathable approach and do it properly!

 

[Spoilt Victorian Child]

Vinyl papers would likely cause an issue due to the plastic coating, but my research suggests traditional papers and lining papers hung using traditional paste are fine.

I'm not sure if mine was vinyl, it wasn't that shiny spit n wipe stuff, it was matt. But it would've come from the likes of B&Q in the early 90s.

What would be a traditional breathable paste? Does anyone have any tried and tested brands/products?

 

[Abi Cott]

A quick Google search suggests Volvox is a brand to look for. Earthborn also do a paste which might be worth looking into.

 

[livias]

Well ... traditional wallpaper paste is flour and water and a splash of bleach to stop it going mouldy. Have to say i have never tried it tho it should be very breathable

 

[lukebasterfield]

We brought a new house back in February which is a conversion of old farm buildings...

Won't this problem be covered for 10 years by some sort of NHBC Builder's Warranty which (I think) is mandatory now for builders/developers?

Having said that, did the developer really understand the building to dot and dab such walls like that? And a chemical injection?? You might want an expert in old buildings to explain why that system isn't suitable/working, suggest the remedy, and use the warranty to pay for it?

Unfortunately the conversion was done 30 years ago, so no warranty! Also, with limited funds, trying to get the work done myself. Already had 3 lots of people round who say the same thing.... it needs a new injected DPC (although there already is one), a membrane layer to stop any water coming through, and new plasterboard. Problem is, none of that fixes the problem, only hides it. In fact, I am shocked that so many 'specialists' advise the same treatment that will only end up causing further damage!
One of them even suggested I had rising damp, despite the lowest course of bricks being dry (where the DPC was injected) and only the 2 layers above showing spalling, and yes, no signs of actual water! I sometime even wonder if there is such a thing as 'rising damp' or is just a favoured term to make potential customers quake in their boots and part with their hard earned cash? Sorry, I am getting sceptical, as I have pretty much given up on finding real help locally as noone seems to specialise around here in period properties, despite the sheer volume of period properties that actually exist!