What is this wall made from?

[Stevers]

Maybe an empty one of these.

https://www.amazon.co.uk/Westland-Organic-Chicken-Manure-Pellets/dp/B006KS5HHW/ref=asc_df_B006KS5HHW?tag=bingshoppinga-21&linkCode=df0&hvadid=79989527879996&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583589102955215&th=1

Correct! Suitable tubs may also contain blood fish & bone, or other fertilizers, and I buy two per year, mainly emptied out on the fruit and veg. gardens. My late father favoured a huge Sandtex paint tub for storing his cement, and he even gave me one that I still use for this. Needless to say I have no use for anything as naff as Sandtex! The 10L Tubs for contract emulsion paints would also work.

 

[Toby Newell]

Finally (and just in time, given the squeezing rental market) bought myself a 1920s semi in a former pit town near Doncaster. I've been going round the place finding the various things that need looking at, old bodges, etc etc; it's like a used car, but bigger and with fewer rusty bits. At any rate, I've a room upstairs that's surplus to requirements for the moment, and clearly has a fair number of problems, so I've decided to set that room aside as a project room. The aim is to get it at least basically habitable for guests by Christmas.

Among other issues, the plaster on the stud wall connecting the two small rooms upstairs is badly blown on the Project Room's side of the wall; when I moved in, I gave it a tap and it moved quite visibly in relation to the wall. I've set to removing the upper layers of plaster, and in the meantime, decided I'd support some shelves the former owners left behind (which were held up just by a couple of battens and a couple of table legs). First problem: Couldn't find the uprights. Some reading suggested the wall should be lath-and-plaster, but try as I might, finding the uprights was impossible. This was not helped by the fact that there's a layer of grey-black plaster, which turns out to be magnetic, on the wall; my guess is it was bulked out using slag from nearby ironworks. In any event, I decided I'd chance just drilling in where the wall sounded most solid. The wall didn't fall down and the shelves are now much better supported. Hurrah.

Today, I decided it was time to chop away a section of the blown black plaster and see what I found underneath. What I've found is below, and distinctly confusing! (Sorry if the pics are too large, please let me know and I'll resize.) It should be added that, so far as I can tell, this is all original and hasn't been altered since construction; indeed, the adjoining room still has what I suspect is its original plaster, complete with rather nice decorative rosettes and swirls.

Now as I understand it, the usual material for stud walls in the 1920s (which is, I'm told, when this place was built) is lath-and-plaster. I can't, so far, find any laths at all in this wall. I've measured the thickness of the white-grey stuff in the pics, and it's about 3/4" thick and rock-hard. (The water marks are from my splashing it to test absorbency, not a damp ingress issue.) The plant material embedded in the grey substance appears to be reeds, not wooden laths; the wall seems to have been built (judging by this section) out of some sort of blocks of the stuff; and the lines horizontal and vertical seem too neat, to me, to be the result of cracking, which makes me think it might be machine-cut. (Again, the thin gouges in the material on the left are from me taking the loose plaster off with a bolster chisel.) I still haven't seen anything to show there are any uprights in this section, and am a bit baffled as to what this material is and what to expect of it. It's certainly stout enough to withstand multiple hits with a cold chisel and a three-pound club hammer with little more than gouges in it (the two crude, square-shaped holes at the bottom of pic #1).

So, what am I up against?

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Don't shoot, but you appear to be drilling light grey, manufactured, possibly early or mid 20th century lightweight ceramic blocks, possibly made from plaster, of which you know nothing about.

FYI these are EXACTLY the type of building material to which asbestos was added to bulk out and increase strength / heat resistance / insulative properties.

Just sayin.

As you were everyone.

 

[Cluemore]

Well, that cheery thought launched me off on a right web dig. This, in turn, has led to my finally finding out who made these things, and from what: A company named Cafferata, primarily a brickworks, based in Newark, not too far away. Some further rummaging then located a brief company history (no sources cited, though some are listed at the end; I'll contact the author at some point), a filing from the US Patent Office (1925), and a brief article about a school in Derby that was built with very similar-sounding stuff (and, judging by the article text, the contractors there went through much the same process of discovery as me). No mentions of the use of asbestos anywhere - I'd especially think the journos would've liked to mention it, since the subtext "and now your school is asbestos-free" is always welcome. I'd also suggest that, given the cut lengths of reed were meant to promote rigidity and strengthen the blocks, while also reducing weight, the addition of asbestos fibres might have seemed unnecessary in the first place. It's not conclusive, as such, but I certainly feel a lot better than I did. I also now have an answer to my question, "What is this wall made from?"

 

[Toby Newell]

Well, that cheery thought launched me off on a right web dig. This, in turn, has led to my finally finding out who made these things, and from what: A company named Cafferata, primarily a brickworks, based in Newark, not too far away. Some further rummaging then located a brief company history (no sources cited, though some are listed at the end; I'll contact the author at some point), a filing from the US Patent Office (1925), and a brief article about a school in Derby that was built with very similar-sounding stuff (and, judging by the article text, the contractors there went through much the same process of discovery as me). No mentions of the use of asbestos anywhere - I'd especially think the journos would've liked to mention it, since the subtext "and now your school is asbestos-free" is always welcome. I'd also suggest that, given the cut lengths of reed were meant to promote rigidity and strengthen the blocks, while also reducing weight, the addition of asbestos fibres might have seemed unnecessary in the first place. It's not conclusive, as such, but I certainly feel a lot better than I did. I also now have an answer to my question, "What is this wall made from?"

Glad it gave you a push! They really did put asbestos really in everything, bitumen for glueing wood blocks? yep. Asbestos was very often added to plaster products, very interesting the use of reeds.

I guess the school bods would of tested an obvious source like that.

Basically it was closer to a modern glass fibre reinforced rebar concrete rather than steel reinforced, because of the weight.

But then horsehair and straw predate that by a few hundred years. Shame they don't try and save more old schools rather than knocking them down. I'm sure Keir were happy about it I've done countless jobs for them in the past.

 

[Drayton]

i haven't been able to open the history so tis may be irrelevant but having a google around myself, they seem to have invented alpha plaster c1930, according to a leaflet by Saint Gobain, who appear to be their sucessors in Newark? If you think it is that, there's an outside chance someone there might know more (if you can find the right person...!) https://www.saintgobainformula.com/.../01/customer_service_charter_uk_-_issue_2.pdf p7

 

[Toby Newell]

i haven't been able to open the history so tis may be irrelevant but having a google around myself, they seem to have invented alpha plaster c1930, according to a leaflet by Saint Gobain, who appear to be their sucessors in Newark? If you think it is that, there's an outside chance someone there might know more (if you can find the right person...!) https://www.saintgobainformula.com/.../01/customer_service_charter_uk_-_issue_2.pdf p7

Saint Gobain bought about a billion companies

 

[Cluemore]

Glad it gave you a push! They really did put asbestos really in everything, bitumen for glueing wood blocks? yep. Asbestos was very often added to plaster products, very interesting the use of reeds.

I guess the school bods would of tested an obvious source like that.

Basically it was closer to a modern glass fibre reinforced rebar concrete rather than steel reinforced, because of the weight.

But then horsehair and straw predate that by a few hundred years. Shame they don't try and save more old schools rather than knocking them down. I'm sure Keir were happy about it I've done countless jobs for them in the past.

It's a fair point; I know asbestos found its way to the most unexpected places. I intend to get a sample tested at some point, just to be on the safe side.

It is good to see an old building being renewed rather than simply pulled down and replaced with some cheaply-built modern pile, I must say. Speaking of, I wasn't aware that concrete was also reinforced with fibreglass; I suppose that's the logical modern successor to asbestos-impregnated concrete. Hopefully, slightly less lethal.

 

[Toby Newell]

It's a fair point; I know asbestos found its way to the most unexpected places. I intend to get a sample tested at some point, just to be on the safe side.

It is good to see an old building being renewed rather than simply pulled down and replaced with some cheaply-built modern pile, I must say. Speaking of, I wasn't aware that concrete was also reinforced with fibreglass; I suppose that's the logical modern successor to asbestos-impregnated concrete. Hopefully, slightly less lethal.

No, the fibreglass is used in lieu of steel rebar, not as in horsehair matrix. It's much better, massive issues with steel rebar corrosion spalling and failure a la Champlain Towers in Miami. All rebar will one day be fibreglass, then carbon fibre. The only steel that should ever be in concrete is tensioning bars because glass or carbon fibre bars do not have the elastic range. I think they tried GF in matrix but now use polymer.

And yes, it was very common to mix asbestos with plaster and possibly concrete, they literally put it in everything!

 

[andyrew1]

Just to pick up on the digression, small glass fibre mixed through the concrete is used quite a bit for certain cases. It can be good for crack control and for when doing small dimensions like decorative panels (see MUCEM in Marseille).

I think we are a long way off replacing all steel with GFRP, it has quite a lot of advantages, but the ductile behaviour of steel reinforcement can't be well replicated at the moment as far as I am aware. And steel is just so cheap, familiar and readily available it'll take a long time to move the construction industry on from it!

Slightly more on topic your blocks @Cluemore remind me a lot of the modern carreaux de plâtre used in France for internal, walls obviously with the addition of the reeds.

 

[Toby Newell]

Just to pick up on the digression, small glass fibre mixed through the concrete is used quite a bit for certain cases. It can be good for crack control and for when doing small dimensions like decorative panels (see MUCEM in Marseille).

I think we are a long way off replacing all steel with GFRP, it has quite a lot of advantages, but the ductile behaviour of steel reinforcement can't be well replicated at the moment as far as I am aware. And steel is just so cheap, familiar and readily available it'll take a long time to move the construction industry on from it!

Slightly more on topic your blocks @Cluemore remind me a lot of the modern carreaux de plâtre used in France for internal, walls obviously with the addition of the reeds.

Yes, in small sections lack of corrosion trumps ductility, in larger sections there are often pre-stressed members which of course have to have a large plastic range. GFRP resins these days have a high enough modulus to work well for most purposes and yes the reason for their slow uptake is due to cost.

Interesting that straw, sticks and horsehair all work on the same principles. Never ceases to delight me when I find intact 400 or 500 year old wattle and daub still doing it's stuff.

FYI at the time you mention Saint Gobain were primarily known for their glass technology being world leaders in the field so it's possible they were early adopters of using glass fibre in the early 1930s.

 

[Chris G]

Finally (and just in time, given the squeezing rental market) bought myself a 1920s semi in a former pit town near Doncaster. I've been going round the place finding the various things that need looking at, old bodges, etc etc; it's like a used car, but bigger and with fewer rusty bits. At any rate, I've a room upstairs that's surplus to requirements for the moment, and clearly has a fair number of problems, so I've decided to set that room aside as a project room. The aim is to get it at least basically habitable for guests by Christmas.

Among other issues, the plaster on the stud wall connecting the two small rooms upstairs is badly blown on the Project Room's side of the wall; when I moved in, I gave it a tap and it moved quite visibly in relation to the wall. I've set to removing the upper layers of plaster, and in the meantime, decided I'd support some shelves the former owners left behind (which were held up just by a couple of battens and a couple of table legs). First problem: Couldn't find the uprights. Some reading suggested the wall should be lath-and-plaster, but try as I might, finding the uprights was impossible. This was not helped by the fact that there's a layer of grey-black plaster, which turns out to be magnetic, on the wall; my guess is it was bulked out using slag from nearby ironworks. In any event, I decided I'd chance just drilling in where the wall sounded most solid. The wall didn't fall down and the shelves are now much better supported. Hurrah.

Today, I decided it was time to chop away a section of the blown black plaster and see what I found underneath. What I've found is below, and distinctly confusing! (Sorry if the pics are too large, please let me know and I'll resize.) It should be added that, so far as I can tell, this is all original and hasn't been altered since construction; indeed, the adjoining room still has what I suspect is its original plaster, complete with rather nice decorative rosettes and swirls.

Now as I understand it, the usual material for stud walls in the 1920s (which is, I'm told, when this place was built) is lath-and-plaster. I can't, so far, find any laths at all in this wall. I've measured the thickness of the white-grey stuff in the pics, and it's about 3/4" thick and rock-hard. (The water marks are from my splashing it to test absorbency, not a damp ingress issue.) The plant material embedded in the grey substance appears to be reeds, not wooden laths; the wall seems to have been built (judging by this section) out of some sort of blocks of the stuff; and the lines horizontal and vertical seem too neat, to me, to be the result of cracking, which makes me think it might be machine-cut. (Again, the thin gouges in the material on the left are from me taking the loose plaster off with a bolster chisel.) I still haven't seen anything to show there are any uprights in this section, and am a bit baffled as to what this material is and what to expect of it. It's certainly stout enough to withstand multiple hits with a cold chisel and a three-pound club hammer with little more than gouges in it (the two crude, square-shaped holes at the bottom of pic #1).

So, what am I up against?

View attachment 10641 View attachment 10643 View attachment 10644

Hi we have found an internal wall in my daughters house exactly like this, part of the plaster has blown which we have removed but the rest is solid can I ask what did you use to replaster it?

 

[Cluemore]

Hi we have found an internal wall in my daughters house exactly like this, part of the plaster has blown which we have removed but the rest is solid can I ask what did you use to replaster it?

Hi Chris, sorry for the very late reply. I've been using Thistle bonding coat and Thistle finish coat; seems to be sticking well, and goes on easily enough. I've applied it to a thickness matching that of the original as closely as I can - about 11-12mm all in all (though it did vary a bit). It's a bloody laborious process, though, and makes me realise why plasterboard was invented!