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?
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
What colour are the bricks?
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.
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
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.
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?
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.