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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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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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"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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