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N. Thornton
 
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Default Spalling

From: Mary Fisher )

wrote in message
oups.com...

We have a few bricks on the front of the round bay window near the

ground
and below the dpc. We haven't worried about it and we don't notice

it. Few
others could see it because of the planting (not touching the wall).

But in the light of what you said I wonder if it would be useful to

re-face
the bricks with (exactly matching) resin-based mastic?



Thats where it usually happens, due to damp freezing in the bricks.
Resin makes that dampness worse by preventing evaporation from the
bricks.

I've never tried refacing bricks, but have only ever heard one thing:
it doesnt last.

I'd check the ground levels relative to the dpc, ground should be 6"
below it, and if the damage isnt bad enough to affect structural
strength, leave it. Or if theyre bad, or an eyesore, replace em.

Cement pointing on old properties is a cause of this: lime pointing
allows more water movement and evaporation, cement prevents it
somewhat. Also old houses tend to move a bit, cement wont move at all,
and is stronger than the brick, so the bricks get damaged. Lime is
soft enough not not cause damage, and the lime will crack rather than
the brick, which is much preferable. Lime cracks are self healing, it
slowly grows hard crystals across the crack by reacting with CO2.


NT
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Mary Fisher
 
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Default


"N. Thornton" wrote in message
om...

We have a few bricks on the front of the round bay window near the

ground
and below the dpc. We haven't worried about it and we don't notice

it. Few
others could see it because of the planting (not touching the wall).

But in the light of what you said I wonder if it would be useful to

re-face
the bricks with (exactly matching) resin-based mastic?



Thats where it usually happens, due to damp freezing in the bricks.
Resin makes that dampness worse by preventing evaporation from the
bricks.


But it's happening anyway, with nothing preventing evaporation :-)

I've never tried refacing bricks, but have only ever heard one thing:
it doesnt last.


Nothing lasts :-(

The affected bricks aren't lasting as well as the unaffected ones although
neither has had any treatment.

I'd check the ground levels relative to the dpc, ground should be 6"
below it,


It is. It's only the odd brick, not all of them.

and if the damage isnt bad enough to affect structural
strength, leave it.


It won't be affecting the structure.

Or if theyre bad, or an eyesore, replace em.


They don't bother us. We're the ones who matter.

Cement pointing on old properties is a cause of this: lime pointing
allows more water movement and evaporation, cement prevents it
somewhat. Also old houses tend to move a bit, cement wont move at all,
and is stronger than the brick, so the bricks get damaged. Lime is
soft enough not not cause damage, and the lime will crack rather than
the brick, which is much preferable. Lime cracks are self healing, it
slowly grows hard crystals across the crack by reacting with CO2.


Well, what do you mean by 'old'?

I don't think of our house as old because I've known it all my life, it was
built in 1937.

Most of the houses here have the spalling, none has been rendered, some have
been cement pointed, we mastic pointed ours when we moved in 40 years ago.
Others' cement pointing hasn't lasted as long. Lime mortar isn't suitable
for our houses, in my opinion - but I'm not an expert. I've only ever seen
it used on stone building though. Believe me, if we had a stone built house
we'd only have used lime based mortar and pointing.

Thanks for your observations.

Mary



NT



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