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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Black mortar
I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? |
#2
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Black mortar
In article , Conrad Edwards
writes I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? As your account seems to suggest that the mortar was friable all the way through the walls, I'd not have supposed it was due to acidic rain. It seems more likely that the mortar had been tinted to match the bricks -- or to contrast with the bricks -- whilst the powdery nature of the mortar may have been due to the phlogistogen content of the materials used. What colour are the bricks? -- Paul |
#3
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Black mortar
Conrad Edwards wrote: I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? I've got a couple of barns built with stone and black mortar. My understanding is that this is from ash added to the mortar. No idea why this was done. I add black pigment to any mortar when making repairs. |
#4
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Black mortar
It's my guess that the mortar has had soot mixed with it to give it a dark
colour (cheap solution). I remember seeing this done 40 years ago. Unfortunately soot doesn't bond well with cement and if the builder mixed in an excessive amount it would eventually wash away leaving you with a honeycomb effect. You might get away with hacking out an inch or so and repointing. Good luck. Robin "Conrad Edwards" wrote in message ... I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? |
#5
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Black mortar
Black and powdery tends to indicate soot and a weak cement or lime
mix. Was it a coal store? Acid does not turn the mortar black, and only really occurs in chinmeys due to flue gases. Depending on the use of the wall and how loose the bricks are, then pointing may suffice. Weak mortar does not necessarily mean an unsound wall, so if it's not too high and relatively stable, then repoint it. However pointing will not increase the walls strength - just increase its' weather resitance Give it a good jet wash or hose down first though. dg Conrad Edwards wrote in message . .. I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? |
#6
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Black mortar
"Conrad Edwards" wrote in message ... I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? This is more than likely a black ash mortar ... if the wall is sound, just re-point but use a lime based mortar rather than OPC, it will work better with an ash mortar. Rick |
#7
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Black mortar
"Rick Hughes" wrote in message ...
"Conrad Edwards" wrote in message ... I've been knocking down an old (maybe 1950s) brick built shed, and it seems like most of the mortar is black and powdery. Is this acid-rain attack? I've left one wall standing...was going to repoint the bricks....this wall appears stable, so would repointing substantially uprate the strength of the wall or should I take it all down and try bricklaying? This is more than likely a black ash mortar ... if the wall is sound, just re-point but use a lime based mortar rather than OPC, it will work better with an ash mortar. Rick The bricks are just the standard red colour, nothing fancy. The area used to be quite middle class in the 30s when the house was built, I'm guessing the garage was added in the 50s-60s (and a council estate was built nearby in the 60s), so maybe it was done just to look posher than the ones down the road? |
#8
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